Belt printer: qualify Slic3r::Polygon in the blocker-index test (#16196 )

Fixes the Windows x64 and arm64 build failures on `belt-printer` after #16195: `tests/fff_print/test_print.cpp` includes `<Windows.h>`, so the unqualified `Polygon` in the new TreeModelVolumes blocker test is ambiguous with GDI's `Polygon()` (`error: reference to 'Polygon' is ambiguous`). It is the only error in both logs. The type is now written `Slic3r::Polygon`.
Qualify Slic3r::Polygon in the blocker-index test
2026-10-06 15:21:09 +00:00 · 2026-10-06 00:23:50 -05:00 · 2026-10-06 00:12:59 -05:00 · 2026-10-05 23:20:23 -05:00 · 2026-10-05 23:19:41 -05:00 · 2026-10-05 23:06:01 -05:00
183 changed files with 13522 additions and 1092 deletions
@@ -74,12 +74,26 @@ jobs:
          set +e
          ./OrcaSlicer_profile_validator -p ${{ github.workspace }}/resources/profiles -l 2 2>&1 | tee ${{ runner.temp }}/validate_system.log
          exit ${PIPESTATUS[0]}
+      # The validator above is the nightly build of main, so it cannot slice profiles that use
+      # settings a PR adds to the engine: it reports their placeholders as undefined. A PR that
+      # changes src/ also runs Build all, whose Slice check runs this same sweep with the
+      # validator built from the PR, so the sweep below only runs for the other PRs.
+      - name: Detect engine changes
+        id: engine_changes
+        if: ${{ github.event_name == 'pull_request' }}
+        run: |
+          base=${{ github.event.pull_request.base.sha }}
+          if git fetch --no-tags --depth=1 origin "$base" && ! git diff --quiet "$base" HEAD -- src/; then
+            echo "changed=true" >> "$GITHUB_OUTPUT"
+            echo "::notice::This PR changes src/, so Build all's Slice check slices the profiles with the PR-built validator."
+          fi
      # Slice a two-colour cube through every printer, and through every system process/filament whose
      # templates no printer's own slice reaches, so every custom g-code and filename_format shipped is
      # expanded (names in {if} branches not taken included) - catches undefined-placeholder /
      # invalid-flow bugs the static checks above cannot see.
      - name: validate slice (expand custom g-code)
        id: validate_slice
+        if: ${{ steps.engine_changes.outputs.changed != 'true' }}
        continue-on-error: true
        run: |
          set +e
@@ -88,6 +88,18 @@ struct NfpPConfig {
     */
    bool explore_holes = false;

+    /**
+     * @brief Keep the final pile on the bin.
+     *
+     * The final alignment centres the pile on the alignment target. A target
+     * near an edge (a belt printer starts its parts at the leading end of the
+     * belt) would push part of a pile that is larger than the room around that
+     * point off the bed; with this set the pile stops at the edge instead, and a
+     * pile that does not fit along an axis is centred on it. Off by default, so
+     * the alignment of every other printer is unchanged.
+     */
+    bool clamp_to_bin = false;
+
    /**
     * @brief If true, use all CPUs available. Run on a single core otherwise.
     */
@@ -1111,7 +1123,24 @@ private:
        default: ; // DONT_ALIGN
        }

-        auto d = cb - ci;       
+        auto d = cb - ci;
+
+        // Keep the pile on the bin (see Config::clamp_to_bin). The items' boxes carry
+        // their inflation, which is the margin left at the edge.
+        if (config_.clamp_to_bin) {
+            auto on_bin = [](Coord lo, Coord hi, Coord bin_lo, Coord bin_hi, Coord shift) {
+                if (hi - lo >= bin_hi - bin_lo)
+                    return (bin_lo + bin_hi) / 2 - (lo + hi) / 2;
+                if (lo + shift < bin_lo)
+                    shift = bin_lo - lo;
+                if (hi + shift > bin_hi)
+                    shift = bin_hi - hi;
+                return shift;
+            };
+            setX(d, on_bin(getX(bb.minCorner()), getX(bb.maxCorner()), getX(bbin.minCorner()), getX(bbin.maxCorner()), getX(d)));
+            setY(d, on_bin(getY(bb.minCorner()), getY(bb.maxCorner()), getY(bbin.minCorner()), getY(bbin.maxCorner()), getY(d)));
+            cb = ci + d;
+        }

        // BBS make sure the item won't clash with excluded regions
        // do we have wipe tower after arranging?
@@ -0,0 +1,79 @@
+#!/usr/bin/env python3
+"""Belt temperature-tower asset generator (discrete-provini design).
+
+A vertical temperature tower cannot be sliced on a belt printer, so lay a row of
+DISCRETE provini (one per temperature) along the belt (designed Y) with a fixed
+surface gap. Each provino is the chevron+arc unit (belt_temp_provino_unit.stl,
+keel-first); its temperature is ENGRAVED upright into the 50 mm face — a raised
+number would be an unsupported overhang on the belt. The C++ calib_temp belt branch
+(Plater.cpp) injects one M104 per zone 70 layers INTO provino i:
+  print_z[i] = i * PITCH * cos(theta) + 70 * layer_height   (theta = 45)
+inside the body, not in the empty inter-provino gap (which has no sliced layers for
+the event to attach to). PITCH below is the shared geometry contract with that code —
+keep them in sync.
+
+Generates one STL per filament temp range used by Temp_Calibration_Dlg.
+"""
+import numpy as np, trimesh, os
+from matplotlib.textpath import TextPath
+from matplotlib.font_manager import FontProperties
+from shapely.geometry import Polygon as ShPoly
+from shapely.ops import unary_union
+
+HERE = os.path.dirname(os.path.abspath(__file__))
+UNIT = os.path.join(HERE, 'belt_temp_provino_unit.stl')   # single provino, keel-first
+SURF_GAP = 25.0            # surface-to-surface gap between provini (mm) — user spec
+TEXT_H = 9.0
+TEXT_DEPTH = 0.8           # engraving depth (numbers are CUT into the face, not raised:
+                          # a raised number is an unsupported Y-overhang on the belt)
+TEXT_OVERSHOOT = 0.6       # extra height poking out of the face for a clean boolean cut
+
+# Temperature ranges (start, end) per filament family, 5 C step. File name encodes them.
+RANGES = [(230,190),(270,230),(250,230),(280,240),(240,210),(320,280)]
+
+unit = trimesh.load(UNIT)
+dY = unit.bounds[1,1] - unit.bounds[0,1]
+PITCH = dY + SURF_GAP                       # designed-Y pitch == C++ contract constant
+print(f"unit dY={dY:.2f}  PITCH={PITCH:.3f}  (C++ contract: print_z[i]=i*{PITCH:.3f}*cos45)")
+
+# 50 mm face normal (0,-1,1)/sqrt2 ; UPRIGHT basis u=+X det(+1) (verified non-mirrored)
+n = np.array([0,-1,1.])/np.sqrt(2)
+u = np.array([1,0,0.]); v = np.array([0,1,1.])/np.sqrt(2)
+R = np.column_stack([u,v,n])
+fn = unit.face_normals; fc = unit.triangles_center; fa = unit.area_faces
+sel = (fn@n) > 0.9
+face_c = (fc[sel]*fa[sel,None]).sum(0)/fa[sel].sum()
+
+def text_mesh(s):
+    tp = TextPath((0,0), s, size=TEXT_H, prop=FontProperties(family='DejaVu Sans'))
+    rings = [ShPoly(p) for p in tp.to_polygons() if len(p)>=3]
+    rings.sort(key=lambda r:r.area, reverse=True)
+    used=[False]*len(rings); parts=[]
+    for i,o in enumerate(rings):
+        if used[i]: continue
+        holes=[]
+        for j in range(i+1,len(rings)):
+            if not used[j] and o.contains(rings[j]): holes.append(rings[j].exterior.coords); used[j]=True
+        parts.append(ShPoly(o.exterior.coords,holes)); used[i]=True
+    poly = unary_union(parts)
+    geoms = list(poly.geoms) if poly.geom_type=='MultiPolygon' else [poly]
+    m = trimesh.util.concatenate([trimesh.creation.extrude_polygon(g,height=TEXT_DEPTH+TEXT_OVERSHOOT) for g in geoms])
+    c = m.bounds.mean(axis=0); m.apply_translation([-c[0],-c[1],0]); return m
+
+for t_start, t_end in RANGES:
+    temps = list(range(t_start, t_end-1, -5))
+    parts=[]
+    for i,T in enumerate(temps):
+        c = unit.copy(); c.apply_translation([0, i*PITCH, 0])
+        t = text_mesh(str(T)); M=np.eye(4); M[:3,:3]=R; t.apply_transform(M)
+        # place the text spanning from TEXT_DEPTH inside the face to TEXT_OVERSHOOT outside,
+        # then CUT it out of the provino (engrave) — no raised material, no Y-overhang.
+        t.apply_translation(face_c - n*TEXT_DEPTH + np.array([0,i*PITCH,0]))
+        c = trimesh.boolean.difference([c, t], engine='manifold')
+        parts.append(c)
+    asset = trimesh.util.concatenate(parts)
+    out = os.path.join(HERE, f"belt_temp_tower_{t_start}_{t_end}.stl")
+    asset.export(out)
+    dims = np.round(asset.bounds[1]-asset.bounds[0],1)
+    wt = all(p.is_watertight for p in parts)
+    print(f"  {t_start}->{t_end}: {len(temps)} zones  bbox={dims}  watertight={wt}  -> {os.path.basename(out)}")
@@ -1,9 +1,13 @@
 {
 	"name": "Custom Printer",
-	"version": "02.04.00.07",
+	"version": "02.04.00.08",
 	"force_update": "0",
 	"description": "My configurations",
 	"machine_model_list": [
+		{
+			"name": "Generic Belt Printer",
+			"sub_path": "machine/MyBeltPrinter.json"
+		},
 		{
 			"name": "Generic Klipper Printer",
 			"sub_path": "machine/MyKlipper.json"
@@ -50,6 +54,10 @@
 			"name": "0.08mm Extra Fine @MyKlipper",
 			"sub_path": "process/0.08mm Extra Fine @MyKlipper.json"
 		},
+		{
+			"name": "0.12mm Fine @MyBeltPrinter",
+			"sub_path": "process/0.12mm Fine @MyBeltPrinter.json"
+		},
 		{
 			"name": "0.12mm Fine @MyKlipper",
 			"sub_path": "process/0.12mm Fine @MyKlipper.json"
@@ -62,6 +70,10 @@
 			"name": "0.16mm Optimal @MyKlipper",
 			"sub_path": "process/0.16mm Optimal @MyKlipper.json"
 		},
+		{
+			"name": "0.20mm Standard @MyBeltPrinter",
+			"sub_path": "process/0.20mm Standard @MyBeltPrinter.json"
+		},
 		{
 			"name": "0.20mm Standard @MyKlipper",
 			"sub_path": "process/0.20mm Standard @MyKlipper.json"
@@ -262,6 +274,10 @@
 			"name": "MyKlipper 0.8 nozzle",
 			"sub_path": "machine/MyKlipper 0.8 nozzle.json"
 		},
+		{
+			"name": "fdm_belt_common",
+			"sub_path": "machine/fdm_belt_common.json"
+		},
 		{
 			"name": "fdm_toolchanger_common",
 			"sub_path": "machine/fdm_toolchanger_common.json"
@@ -274,6 +290,22 @@
 			"name": "MyRRF 0.4 nozzle",
 			"sub_path": "machine/MyRRF 0.4 nozzle.json"
 		},
+		{
+			"name": "MyBeltPrinter 0.2 nozzle",
+			"sub_path": "machine/MyBeltPrinter 0.2 nozzle.json"
+		},
+		{
+			"name": "MyBeltPrinter 0.4 nozzle",
+			"sub_path": "machine/MyBeltPrinter 0.4 nozzle.json"
+		},
+		{
+			"name": "MyBeltPrinter 0.6 nozzle",
+			"sub_path": "machine/MyBeltPrinter 0.6 nozzle.json"
+		},
+		{
+			"name": "MyBeltPrinter 0.8 nozzle",
+			"sub_path": "machine/MyBeltPrinter 0.8 nozzle.json"
+		},
 		{
 			"name": "MyToolChanger 0.2 nozzle",
 			"sub_path": "machine/MyToolChanger 0.2 nozzle.json"
@@ -0,0 +1,27 @@
+{
+	"type": "machine",
+	"name": "MyBeltPrinter 0.2 nozzle",
+	"inherits": "fdm_belt_common",
+	"from": "system",
+	"setting_id": "3w1uyJdmm14QhDnH",
+	"instantiation": "true",
+	"printer_model": "Generic Belt Printer",
+	"default_print_profile": "0.12mm Fine @MyBeltPrinter",
+	"nozzle_diameter": [
+		"0.2"
+	],
+	"max_layer_height": [
+		"0.16"
+	],
+	"min_layer_height": [
+		"0.04"
+	],
+	"printer_variant": "0.2",
+	"printable_area": [
+		"0x0",
+		"350x0",
+		"350x350",
+		"0x350"
+	],
+	"printable_height": "300"
+}
@@ -0,0 +1,20 @@
+{
+	"type": "machine",
+	"name": "MyBeltPrinter 0.4 nozzle",
+	"inherits": "fdm_belt_common",
+	"from": "system",
+	"setting_id": "6nRHUtvJOUffocbu",
+	"instantiation": "true",
+	"printer_model": "Generic Belt Printer",
+	"nozzle_diameter": [
+		"0.4"
+	],
+	"printer_variant": "0.4",
+	"printable_area": [
+		"0x0",
+		"350x0",
+		"350x350",
+		"0x350"
+	],
+	"printable_height": "300"
+}
@@ -0,0 +1,26 @@
+{
+	"type": "machine",
+	"name": "MyBeltPrinter 0.6 nozzle",
+	"inherits": "fdm_belt_common",
+	"from": "system",
+	"setting_id": "K0m9HbUNwKT4UCJV",
+	"instantiation": "true",
+	"printer_model": "Generic Belt Printer",
+	"nozzle_diameter": [
+		"0.6"
+	],
+	"max_layer_height": [
+		"0.4"
+	],
+	"min_layer_height": [
+		"0.12"
+	],
+	"printer_variant": "0.6",
+	"printable_area": [
+		"0x0",
+		"350x0",
+		"350x350",
+		"0x350"
+	],
+	"printable_height": "300"
+}
@@ -0,0 +1,26 @@
+{
+	"type": "machine",
+	"name": "MyBeltPrinter 0.8 nozzle",
+	"inherits": "fdm_belt_common",
+	"from": "system",
+	"setting_id": "rHAweDz4eNwttPNA",
+	"instantiation": "true",
+	"printer_model": "Generic Belt Printer",
+	"nozzle_diameter": [
+		"0.8"
+	],
+	"max_layer_height": [
+		"0.6"
+	],
+	"min_layer_height": [
+		"0.2"
+	],
+	"printer_variant": "0.8",
+	"printable_area": [
+		"0x0",
+		"350x0",
+		"350x350",
+		"0x350"
+	],
+	"printable_height": "300"
+}
@@ -0,0 +1,12 @@
+{
+	"type": "machine_model",
+	"name": "Generic Belt Printer",
+	"model_id": "my_belt_01",
+	"nozzle_diameter": "0.4;0.2;0.6;0.8",
+	"machine_tech": "FFF",
+	"family": "MyPrinter",
+	"bed_model": "Custom_350_bed.stl",
+	"bed_texture": "orcaslicer_bed_texture.svg",
+	"hotend_model": "",
+	"default_materials": "Generic PLA @System;Generic PLA-CF @System;Generic PETG @System;Generic TPU @System;Generic PC @System;Generic PVA @System;Generic PA @System;Generic PA-CF @System"
+}
@@ -0,0 +1,96 @@
+{
+	"type": "machine",
+	"name": "fdm_belt_common",
+	"inherits": "fdm_klipper_common",
+	"from": "system",
+	"instantiation": "false",
+	"gcode_flavor": "klipper",
+	"single_extruder_multi_material": "0",
+	"default_filament_profile": [
+		"Generic PLA @System"
+	],
+	"default_print_profile": "0.20mm Standard @MyBeltPrinter",
+	"max_layer_height": [
+		"0.32"
+	],
+	"min_layer_height": [
+		"0.08"
+	],
+	"deretraction_speed": [
+		"30"
+	],
+	"extruder_colour": [
+		"#FCE94F"
+	],
+	"extruder_offset": [
+		"0x0"
+	],
+	"long_retractions_when_cut": [
+		"0"
+	],
+	"nozzle_diameter": [
+		"0.4"
+	],
+	"retract_before_wipe": [
+		"70%"
+	],
+	"retract_length_toolchange": [
+		"2"
+	],
+	"retract_lift_above": [
+		"0"
+	],
+	"retract_lift_below": [
+		"0"
+	],
+	"retract_lift_enforce": [
+		"All Surfaces"
+	],
+	"retract_restart_extra": [
+		"0"
+	],
+	"retract_restart_extra_toolchange": [
+		"0"
+	],
+	"retract_when_changing_layer": [
+		"1"
+	],
+	"retraction_distances_when_cut": [
+		"18"
+	],
+	"retraction_length": [
+		"0.8"
+	],
+	"retraction_minimum_travel": [
+		"1"
+	],
+	"retraction_speed": [
+		"30"
+	],
+	"travel_slope": [
+		"3"
+	],
+	"wipe": [
+		"1"
+	],
+	"wipe_distance": [
+		"1"
+	],
+	"z_hop": [
+		"0"
+	],
+	"z_hop_types": [
+		"Normal Lift"
+	],
+	"gcode_remap_x": "rev_x",
+	"gcode_remap_y": "pos_z",
+	"gcode_remap_z": "pos_y",
+	"belt_printer": "1",
+	"belt_slice_rotation": "x",
+	"belt_slice_rotation_angle": "45",
+	"belt_slice_rotation_global": "1",
+	"build_plate_tilt_x": "45",
+	"purge_in_prime_tower": "0",
+	"scan_first_layer": "0",
+	"auxiliary_fan": "0"
+}
@@ -0,0 +1,20 @@
+{
+	"type": "process",
+	"name": "0.12mm Fine @MyBeltPrinter",
+	"inherits": "fdm_process_klipper_common",
+	"from": "system",
+	"setting_id": "EugqqdLJ423bgEwN",
+	"instantiation": "true",
+	"layer_height": "0.12",
+	"initial_layer_print_height": "0.12",
+	"bottom_shell_layers": "5",
+	"top_shell_layers": "6",
+	"support_top_z_distance": "0.08",
+	"support_bottom_z_distance": "0.08",
+	"skirt_loops": "0",
+	"skirt_distance": "0",
+	"compatible_printers": [
+		"MyBeltPrinter 0.2 nozzle",
+		"MyBeltPrinter 0.4 nozzle"
+	]
+}
@@ -0,0 +1,17 @@
+{
+	"type": "process",
+	"name": "0.20mm Standard @MyBeltPrinter",
+	"inherits": "fdm_process_klipper_common",
+	"from": "system",
+	"setting_id": "YzCDAgH3uLOM53pF",
+	"instantiation": "true",
+	"layer_height": "0.2",
+	"initial_layer_print_height": "0.2",
+	"skirt_loops": "0",
+	"skirt_distance": "0",
+	"compatible_printers": [
+		"MyBeltPrinter 0.4 nozzle",
+		"MyBeltPrinter 0.6 nozzle",
+		"MyBeltPrinter 0.8 nozzle"
+	]
+}
@@ -0,0 +1,54 @@
+{
+    "name": "IdeaFormer",
+    "version": "02.00.00.06",
+    "force_update": "0",
+    "description": "IdeaFormer belt printer configurations",
+    "machine_model_list": [
+        {
+            "name": "IdeaFormer IR3 V2",
+            "sub_path": "machine/IdeaFormer IR3 V2.json"
+        }
+    ],
+    "process_list": [
+        {
+            "name": "fdm_process_common",
+            "sub_path": "process/fdm_process_common.json"
+        },
+        {
+            "name": "0.20mm Standard @IdeaFormer IR3 V2",
+            "sub_path": "process/0.20mm Standard @IdeaFormer IR3 V2.json"
+        }
+    ],
+    "filament_list": [
+        {
+            "name": "Generic PLA @IdeaFormer IR3 V2",
+            "sub_path": "filament/Generic PLA @IdeaFormer IR3 V2.json"
+        },
+        {
+            "name": "eSUN PLA @IdeaFormer IR3 V2",
+            "sub_path": "filament/eSUN PLA @IdeaFormer IR3 V2.json"
+        },
+        {
+            "name": "Generic PETG @IdeaFormer IR3 V2",
+            "sub_path": "filament/Generic PETG @IdeaFormer IR3 V2.json"
+        }
+    ],
+    "machine_list": [
+        {
+            "name": "fdm_machine_common",
+            "sub_path": "machine/fdm_machine_common.json"
+        },
+        {
+            "name": "fdm_klipper_common",
+            "sub_path": "machine/fdm_klipper_common.json"
+        },
+        {
+            "name": "fdm_belt_common",
+            "sub_path": "machine/fdm_belt_common.json"
+        },
+        {
+            "name": "IdeaFormer IR3 V2 0.4 nozzle",
+            "sub_path": "machine/IdeaFormer IR3 V2 0.4 nozzle.json"
+        }
+    ]
+}
@@ -0,0 +1,77 @@
+{
+	"type": "filament",
+	"name": "Generic PETG @IdeaFormer IR3 V2",
+	"inherits": "Generic PETG @System",
+	"from": "system",
+	"setting_id": "n4zaXcUUzTqAxq5f",
+	"instantiation": "true",
+	"filament_extruder_variant": [
+		"Direct Drive Standard"
+	],
+	"compatible_printers": [
+		"IdeaFormer IR3 V2 0.4 nozzle"
+	],
+	"filament_type": [
+		"PETG"
+	],
+	"filament_vendor": [
+		"Generic"
+	],
+	"filament_settings_id": [
+		"Generic PETG @IdeaFormer IR3 V2"
+	],
+	"filament_flow_ratio": [
+		"0.95"
+	],
+	"filament_cost": [
+		"25"
+	],
+	"nozzle_temperature": [
+		"240"
+	],
+	"nozzle_temperature_initial_layer": [
+		"245"
+	],
+	"cool_plate_temp": [
+		"80"
+	],
+	"cool_plate_temp_initial_layer": [
+		"80"
+	],
+	"fan_min_speed": [
+		"40"
+	],
+	"fan_max_speed": [
+		"60"
+	],
+	"overhang_fan_threshold": [
+		"25%"
+	],
+	"overhang_fan_speed": [
+		"80"
+	],
+	"full_fan_speed_layer": [
+		"8"
+	],
+	"slow_down_min_speed": [
+		"20"
+	],
+	"slow_down_layer_time": [
+		"4"
+	],
+	"fan_cooling_layer_time": [
+		"100"
+	],
+	"filament_retraction_length": [
+		"2"
+	],
+	"filament_retraction_speed": [
+		"40"
+	],
+	"filament_deretraction_speed": [
+		"40"
+	],
+	"filament_start_gcode": [
+		"; Generic PETG @IdeaFormer IR3 V2 — belt PETG, bed 80C"
+	]
+}
@@ -0,0 +1,65 @@
+{
+	"type": "filament",
+	"name": "Generic PLA @IdeaFormer IR3 V2",
+	"inherits": "Generic PLA @System",
+	"from": "system",
+	"setting_id": "1xjycsEAFh6KQIhp",
+	"instantiation": "true",
+	"filament_extruder_variant": [
+		"Direct Drive Standard"
+	],
+	"compatible_printers": [
+		"IdeaFormer IR3 V2 0.4 nozzle"
+	],
+	"filament_type": [
+		"PLA"
+	],
+	"filament_vendor": [
+		"Generic"
+	],
+	"filament_settings_id": [
+		"Generic PLA @IdeaFormer IR3 V2"
+	],
+	"nozzle_temperature": [
+		"215"
+	],
+	"hot_plate_temp": [
+		"75"
+	],
+	"hot_plate_temp_initial_layer": [
+		"75"
+	],
+	"cool_plate_temp": [
+		"75"
+	],
+	"cool_plate_temp_initial_layer": [
+		"75"
+	],
+	"textured_plate_temp": [
+		"75"
+	],
+	"textured_plate_temp_initial_layer": [
+		"75"
+	],
+	"close_fan_the_first_x_layers": [
+		"3"
+	],
+	"full_fan_speed_layer": [
+		"8"
+	],
+	"slow_down_min_speed": [
+		"20"
+	],
+	"filament_retraction_length": [
+		"1.5"
+	],
+	"filament_retraction_speed": [
+		"35"
+	],
+	"filament_deretraction_speed": [
+		"30"
+	],
+	"filament_start_gcode": [
+		"; Generic PLA @IdeaFormer IR3 V2 — belt PLA, bed 75C"
+	]
+}
@@ -0,0 +1,36 @@
+{
+	"type": "filament",
+	"name": "eSUN PLA @IdeaFormer IR3 V2",
+	"inherits": "Generic PLA @IdeaFormer IR3 V2",
+	"from": "system",
+	"setting_id": "XqkviBmFHEglXueX",
+	"filament_id": "OFkrxQC4",
+	"instantiation": "true",
+	"compatible_printers": [
+		"IdeaFormer IR3 V2 0.4 nozzle"
+	],
+	"filament_type": [
+		"PLA"
+	],
+	"filament_vendor": [
+		"eSUN"
+	],
+	"filament_settings_id": [
+		"eSUN PLA @IdeaFormer IR3 V2"
+	],
+	"nozzle_temperature_initial_layer": [
+		"200"
+	],
+	"nozzle_temperature": [
+		"200"
+	],
+	"enable_pressure_advance": [
+		"1"
+	],
+	"pressure_advance": [
+		"0.12"
+	],
+	"filament_max_volumetric_speed": [
+		"20"
+	]
+}
@@ -0,0 +1,98 @@
+{
+	"type": "machine",
+	"name": "IdeaFormer IR3 V2 0.4 nozzle",
+	"inherits": "fdm_belt_common",
+	"from": "system",
+	"setting_id": "MDQZgwRgg72lmjtu",
+	"instantiation": "true",
+	"printer_model": "IdeaFormer IR3 V2",
+	"printer_variant": "0.4",
+	"nozzle_diameter": [
+		"0.4"
+	],
+	"printable_area": [
+		"0x0",
+		"250x0",
+		"250x2000",
+		"0x2000"
+	],
+	"printable_height": "250",
+	"belt_printer_infinite_y": "1",
+	"thumbnails": [
+		"48x48/PNG",
+		"300x300/PNG"
+	],
+	"default_filament_profile": [
+		"Generic PLA @IdeaFormer IR3 V2"
+	],
+	"default_print_profile": "0.20mm Standard @IdeaFormer IR3 V2",
+	"use_relative_e_distances": "1",
+	"machine_max_acceleration_extruding": [
+		"5000",
+		"5000"
+	],
+	"machine_max_acceleration_retracting": [
+		"1000",
+		"1000"
+	],
+	"machine_max_acceleration_travel": [
+		"9000",
+		"9000"
+	],
+	"machine_max_acceleration_x": [
+		"5000",
+		"5000"
+	],
+	"machine_max_acceleration_y": [
+		"5000",
+		"5000"
+	],
+	"machine_max_acceleration_z": [
+		"100",
+		"100"
+	],
+	"machine_max_jerk_x": [
+		"10",
+		"10"
+	],
+	"machine_max_jerk_y": [
+		"10",
+		"10"
+	],
+	"machine_max_jerk_z": [
+		"0.4",
+		"0.4"
+	],
+	"machine_max_speed_e": [
+		"60",
+		"60"
+	],
+	"machine_max_speed_x": [
+		"500",
+		"500"
+	],
+	"machine_max_speed_y": [
+		"500",
+		"500"
+	],
+	"machine_max_speed_z": [
+		"20",
+		"20"
+	],
+	"retraction_length": [
+		"2"
+	],
+	"retraction_speed": [
+		"40"
+	],
+	"deretraction_speed": [
+		"40"
+	],
+	"retract_lift_below": [
+		"300"
+	],
+	"machine_start_gcode": "; === IdeaFormer IR3 V2 Belt Printer Start ===\n; Axes: X=lateral, Y=gantry height (probe), Z=belt\nG90 ; absolute positioning\nM82 ; absolute extruder\nG21 ; millimeters\nG28 ; home all axes\nG1 Y20 F500 ; lift nozzle 20mm from belt\n; Bed + hotend temps come from the active filament profile. Belt PLA requires 75 C bed — use Generic/eSun PLA @IdeaFormer IR3 V2 filament presets to get it automatically.\nM140 S[hot_plate_temp_initial_layer] ; set bed temp\nM104 S[nozzle_temperature_initial_layer] ; hotend temp\nM109 S[nozzle_temperature_initial_layer] ; wait hotend\nM190 S[hot_plate_temp_initial_layer] ; wait bed\n; --- Purge blob ---\nG92 E0 ; zero extruder\nG1 Y.1 ; nozzle 0.1mm above belt\nG1 E15 F1000 ; purge 15mm blob\nG1 Z20 E25 F800 ; belt advance 20mm + extrude\nG1 E23 ; retract 2mm\nG28 Y ; re-probe belt surface\nG1 E25 ; de-retract\n; --- Prime lines (full 250mm bed width) ---\nFMS_on ; filament motion sensor\nG1 X250 E50 F2000 ; prime line 1\nG92 Z0 ; reset belt origin\nG1 Z.4 ; belt advance 0.4mm\nG1 X0 E75 ; prime line 2\nG1 F1000 ; default feedrate\nG92 E0 Z0 ; zero extruder + belt = print origin\n",
+	"machine_end_gcode": "; === IdeaFormer IR3 V2 Belt Printer End ===\nM400 ; wait for moves to finish\nM104 S0 ; heater off\nM140 S0 ; bed off\nG92 E0 ; zero extruder\nG1 E-5 F300 ; retract 5mm\nG4 P5000 ; wait for ooze\nG91 ; relative mode - keep every end move relative on a belt\nG1 Y20 F1000 ; raise gantry 20mm for clearance over the part\nG1 Z676 F3000 ; advance belt one full machine-depth to eject the part and clean the belt\nG90 ; back to absolute\nG28 X ; home X only - NEVER 'G28' all: that homes Z/belt and reverses the whole print back into the gantry\nFMS_off ; filament motion sensor off\nBED_MESH_CLEAR\nM84 ; disable motors\n",
+	"machine_pause_gcode": "PAUSE",
+	"layer_change_gcode": "G92 E0 ; belt: reset extruder at layer change (relative E)"
+}
@@ -0,0 +1,12 @@
+{
+	"type": "machine_model",
+	"name": "IdeaFormer IR3 V2",
+	"model_id": "IdeaFormer_IR3_V2",
+	"nozzle_diameter": "0.4",
+	"machine_tech": "FFF",
+	"family": "IdeaFormer",
+	"bed_model": "",
+	"bed_texture": "",
+	"hotend_model": "",
+	"default_materials": "Generic PLA @IdeaFormer IR3 V2;Generic PETG @IdeaFormer IR3 V2"
+}
@@ -0,0 +1,99 @@
+{
+	"type": "machine",
+	"name": "fdm_belt_common",
+	"inherits": "fdm_klipper_common",
+	"from": "system",
+	"instantiation": "false",
+	"gcode_flavor": "klipper",
+	"single_extruder_multi_material": "0",
+	"default_filament_profile": [
+		"Generic PLA @System"
+	],
+	"default_print_profile": "0.20mm Standard @IdeaFormer IR3 V2",
+	"max_layer_height": [
+		"0.32"
+	],
+	"min_layer_height": [
+		"0.08"
+	],
+	"deretraction_speed": [
+		"30"
+	],
+	"extruder_colour": [
+		"#FCE94F"
+	],
+	"extruder_offset": [
+		"0x0"
+	],
+	"long_retractions_when_cut": [
+		"0"
+	],
+	"nozzle_diameter": [
+		"0.4"
+	],
+	"retract_before_wipe": [
+		"70%"
+	],
+	"retract_length_toolchange": [
+		"2"
+	],
+	"retract_lift_above": [
+		"0"
+	],
+	"retract_lift_below": [
+		"0"
+	],
+	"retract_lift_enforce": [
+		"All Surfaces"
+	],
+	"retract_restart_extra": [
+		"0"
+	],
+	"retract_restart_extra_toolchange": [
+		"0"
+	],
+	"retract_when_changing_layer": [
+		"1"
+	],
+	"retraction_distances_when_cut": [
+		"18"
+	],
+	"retraction_length": [
+		"0.8"
+	],
+	"retraction_minimum_travel": [
+		"1"
+	],
+	"retraction_speed": [
+		"30"
+	],
+	"travel_slope": [
+		"3"
+	],
+	"wipe": [
+		"1"
+	],
+	"wipe_distance": [
+		"1"
+	],
+	"z_hop": [
+		"0"
+	],
+	"z_hop_types": [
+		"Normal Lift"
+	],
+	"gcode_remap_x": "rev_x",
+	"gcode_remap_y": "pos_z",
+	"gcode_remap_z": "pos_y",
+	"printer_extruder_id": [
+		"1"
+	],
+	"belt_printer": "1",
+	"belt_slice_rotation": "x",
+	"belt_slice_rotation_angle": "45",
+	"belt_slice_rotation_global": "1",
+	"build_plate_tilt_x": "45",
+	"purge_in_prime_tower": "0",
+	"scan_first_layer": "0",
+	"auxiliary_fan": "0"
+}
@@ -0,0 +1,140 @@
+{
+	"type": "machine",
+	"name": "fdm_klipper_common",
+	"inherits": "fdm_machine_common",
+	"from": "system",
+	"instantiation": "false",
+	"gcode_flavor": "klipper",
+	"machine_max_acceleration_e": [
+		"5000",
+		"5000"
+	],
+	"machine_max_acceleration_extruding": [
+		"20000",
+		"20000"
+	],
+	"machine_max_acceleration_retracting": [
+		"5000",
+		"5000"
+	],
+	"machine_max_acceleration_travel": [
+		"20000",
+		"20000"
+	],
+	"machine_max_acceleration_x": [
+		"20000",
+		"20000"
+	],
+	"machine_max_acceleration_y": [
+		"20000",
+		"20000"
+	],
+	"machine_max_acceleration_z": [
+		"500",
+		"200"
+	],
+	"machine_max_speed_e": [
+		"25",
+		"25"
+	],
+	"machine_max_speed_x": [
+		"500",
+		"200"
+	],
+	"machine_max_speed_y": [
+		"500",
+		"200"
+	],
+	"machine_max_speed_z": [
+		"12",
+		"12"
+	],
+	"machine_max_jerk_e": [
+		"2.5",
+		"2.5"
+	],
+	"machine_max_jerk_x": [
+		"9",
+		"9"
+	],
+	"machine_max_jerk_y": [
+		"9",
+		"9"
+	],
+	"machine_max_jerk_z": [
+		"0.2",
+		"0.4"
+	],
+	"machine_min_extruding_rate": [
+		"0",
+		"0"
+	],
+	"machine_min_travel_rate": [
+		"0",
+		"0"
+	],
+	"max_layer_height": [
+		"0.32"
+	],
+	"min_layer_height": [
+		"0.08"
+	],
+	"printable_height": "250",
+	"extruder_clearance_radius": "65",
+	"extruder_clearance_height_to_rod": "36",
+	"extruder_clearance_height_to_lid": "140",
+	"printer_settings_id": "",
+	"printer_technology": "FFF",
+	"printer_variant": "0.4",
+	"retraction_minimum_travel": [
+		"1"
+	],
+	"retract_before_wipe": [
+		"70%"
+	],
+	"retract_when_changing_layer": [
+		"1"
+	],
+	"retraction_length": [
+		"0.8"
+	],
+	"retract_length_toolchange": [
+		"2"
+	],
+	"z_hop": [
+		"0.4"
+	],
+	"retract_restart_extra": [
+		"0"
+	],
+	"retract_restart_extra_toolchange": [
+		"0"
+	],
+	"retraction_speed": [
+		"30"
+	],
+	"deretraction_speed": [
+		"30"
+	],
+	"z_hop_types": "Normal Lift",
+	"single_extruder_multi_material": "1",
+	"change_filament_gcode": "",
+	"wipe": [
+		"1"
+	],
+	"default_filament_profile": [
+		"Generic PLA @System"
+	],
+	"default_print_profile": "0.20mm Standard @MyKlipper",
+	"bed_exclude_area": [
+		"0x0"
+	],
+	"machine_start_gcode": "M190 S[bed_temperature_initial_layer_single]\nM109 S[nozzle_temperature_initial_layer]\nPRINT_START EXTRUDER=[nozzle_temperature_initial_layer] BED=[bed_temperature_initial_layer_single]\n",
+	"machine_end_gcode": "PRINT_END",
+	"layer_change_gcode": ";AFTER_LAYER_CHANGE\n;[layer_z]",
+	"before_layer_change_gcode": ";BEFORE_LAYER_CHANGE\n;[layer_z]\nG92 E0\n",
+	"machine_pause_gcode": "PAUSE",
+	"scan_first_layer": "0",
+	"nozzle_type": "undefine",
+	"auxiliary_fan": "0"
+}
@@ -0,0 +1,118 @@
+{
+	"type": "machine",
+	"name": "fdm_machine_common",
+	"from": "system",
+	"instantiation": "false",
+	"printer_technology": "FFF",
+	"deretraction_speed": [
+		"40"
+	],
+	"extruder_colour": [
+		"#FCE94F"
+	],
+	"extruder_offset": [
+		"0x0"
+	],
+	"gcode_flavor": "marlin",
+	"machine_max_acceleration_e": [
+		"5000"
+	],
+	"machine_max_acceleration_extruding": [
+		"10000"
+	],
+	"machine_max_acceleration_retracting": [
+		"1000"
+	],
+	"machine_max_acceleration_x": [
+		"10000"
+	],
+	"machine_max_acceleration_y": [
+		"10000"
+	],
+	"machine_max_acceleration_z": [
+		"500"
+	],
+	"machine_max_speed_e": [
+		"60"
+	],
+	"machine_max_speed_x": [
+		"500"
+	],
+	"machine_max_speed_y": [
+		"500"
+	],
+	"machine_max_speed_z": [
+		"10"
+	],
+	"machine_max_jerk_e": [
+		"5"
+	],
+	"machine_max_jerk_x": [
+		"8"
+	],
+	"machine_max_jerk_y": [
+		"8"
+	],
+	"machine_max_jerk_z": [
+		"0.4"
+	],
+	"machine_min_extruding_rate": [
+		"0"
+	],
+	"machine_min_travel_rate": [
+		"0"
+	],
+	"max_layer_height": [
+		"0.32"
+	],
+	"min_layer_height": [
+		"0.08"
+	],
+	"printable_height": "250",
+	"extruder_clearance_radius": "65",
+	"extruder_clearance_height_to_rod": "36",
+	"extruder_clearance_height_to_lid": "140",
+	"nozzle_diameter": [
+		"0.4"
+	],
+	"printer_settings_id": "",
+	"printer_variant": "0.4",
+	"retraction_minimum_travel": [
+		"2"
+	],
+	"retract_before_wipe": [
+		"70%"
+	],
+	"retract_when_changing_layer": [
+		"1"
+	],
+	"retraction_length": [
+		"1"
+	],
+	"retract_length_toolchange": [
+		"1"
+	],
+	"z_hop": [
+		"0"
+	],
+	"retract_restart_extra": [
+		"0"
+	],
+	"retract_restart_extra_toolchange": [
+		"0"
+	],
+	"retraction_speed": [
+		"60"
+	],
+	"single_extruder_multi_material": "1",
+	"change_filament_gcode": "",
+	"wipe": [
+		"1"
+	],
+	"default_print_profile": "",
+	"machine_start_gcode": "G0 Z20 F9000\nG92 E0; G1 E-10 F1200\nG28\nM970 Q1 A10 B10 C130 K0\nM970 Q1 A10 B131 C250 K1\nM974 Q1 S1 P0\nM970 Q0 A10 B10 C130 H20 K0\nM970 Q0 A10 B131 C250 K1\nM974 Q0 S1 P0\nM220 S100 ;Reset Feedrate\nM221 S100 ;Reset Flowrate\nG29 ;Home\nG90;\nG92 E0 ;Reset Extruder \nG1 Z2.0 F3000 ;Move Z Axis up \nG1 X10.1 Y20 Z0.28 F5000.0 ;Move to start position\nM109 S205;\nG1 X10.1 Y200.0 Z0.28 F1500.0 E15 ;Draw the first line\nG1 X10.4 Y200.0 Z0.28 F5000.0 ;Move to side a little\nG1 X10.4 Y20 Z0.28 F1500.0 E30 ;Draw the second line\nG92 E0 ;Reset Extruder \nG1 X110 Y110 Z2.0 F3000 ;Move Z Axis up",
+	"machine_end_gcode": "M400 ; wait for buffer to clear\nG92 E0 ; zero the extruder\nG1 E-4.0 F3600; retract \nG91\nG1 Z3;\nM104 S0 ; turn off hotend\nM140 S0 ; turn off bed\nM106 S0 ; turn off fan\nG90 \nG0 X110 Y200 F3600 \nprint_end",
+	"layer_change_gcode": ";AFTER_LAYER_CHANGE\n;[layer_z]",
+	"before_layer_change_gcode": ";BEFORE_LAYER_CHANGE\n;[layer_z]\nG92 E0\n",
+	"machine_pause_gcode": "M601"
+}
@@ -0,0 +1,23 @@
+{
+	"type": "process",
+	"name": "0.20mm Standard @IdeaFormer IR3 V2",
+	"inherits": "fdm_process_common",
+	"from": "system",
+	"setting_id": "91atcIwv5728phqX",
+	"instantiation": "true",
+	"layer_height": "0.2",
+	"initial_layer_print_height": "0.2",
+	"initial_layer_line_width": "0.42",
+	"wall_loops": "2",
+	"reduce_infill_retraction": "1",
+	"detect_overhang_wall": "1",
+	"skirt_loops": "0",
+	"skirt_distance": "0",
+	"sparse_infill_pattern": "grid",
+	"sparse_infill_speed": "200",
+	"support_base_pattern": "rectilinear",
+	"support_interface_pattern": "rectilinear",
+	"compatible_printers": [
+		"IdeaFormer IR3 V2 0.4 nozzle"
+	]
+}
@@ -0,0 +1,106 @@
+{
+	"type": "process",
+	"name": "fdm_process_common",
+	"from": "system",
+	"instantiation": "false",
+	"reduce_crossing_wall": "0",
+	"max_travel_detour_distance": "0",
+	"bottom_surface_pattern": "monotonic",
+	"bottom_shell_thickness": "0",
+	"bridge_speed": "50",
+	"brim_width": "5",
+	"brim_object_gap": "0.1",
+	"compatible_printers": [],
+	"compatible_printers_condition": "",
+	"print_sequence": "by layer",
+	"default_acceleration": "1000",
+	"initial_layer_acceleration": "500",
+	"top_surface_acceleration": "1000",
+	"travel_acceleration": "1000",
+	"inner_wall_acceleration": "1000",
+	"outer_wall_acceleration": "700",
+	"bridge_no_support": "0",
+	"draft_shield": "disabled",
+	"elefant_foot_compensation": "0",
+	"enable_arc_fitting": "0",
+	"wall_infill_order": "inner wall/outer wall/infill",
+	"infill_direction": "45",
+	"sparse_infill_density": "15%",
+	"sparse_infill_pattern": "crosshatch",
+	"initial_layer_print_height": "0.2",
+	"infill_combination": "0",
+	"infill_wall_overlap": "25%",
+	"interface_shells": "0",
+	"ironing_flow": "10%",
+	"ironing_spacing": "0.15",
+	"ironing_speed": "30",
+	"ironing_type": "no ironing",
+	"reduce_infill_retraction": "1",
+	"filename_format": "{input_filename_base}_{layer_height}mm_{filament_type[initial_tool]}_{printer_model}_{print_time}.gcode",
+	"detect_overhang_wall": "1",
+	"slowdown_for_curled_perimeters": "1",
+	"overhang_1_4_speed": "0",
+	"overhang_2_4_speed": "50",
+	"overhang_3_4_speed": "30",
+	"overhang_4_4_speed": "10",
+	"line_width": "110%",
+	"inner_wall_line_width": "110%",
+	"outer_wall_line_width": "100%",
+	"top_surface_line_width": "93.75%",
+	"sparse_infill_line_width": "110%",
+	"initial_layer_line_width": "120%",
+	"internal_solid_infill_line_width": "120%",
+	"support_line_width": "96%",
+	"wall_loops": "3",
+	"print_settings_id": "",
+	"raft_layers": "0",
+	"seam_position": "aligned",
+	"skirt_distance": "2",
+	"skirt_height": "3",
+	"min_skirt_length": "4",
+	"skirt_loops": "0",
+	"minimum_sparse_infill_area": "15",
+	"spiral_mode": "0",
+	"standby_temperature_delta": "-5",
+	"enable_support": "0",
+	"resolution": "0.012",
+	"support_type": "normal(auto)",
+	"support_on_build_plate_only": "0",
+	"support_top_z_distance": "0.2",
+	"support_bottom_z_distance": "0.2",
+	"support_filament": "0",
+	"support_interface_loop_pattern": "0",
+	"support_interface_filament": "0",
+	"support_interface_top_layers": "2",
+	"support_interface_bottom_layers": "2",
+	"support_interface_spacing": "0.5",
+	"support_interface_speed": "80",
+	"support_base_pattern": "default",
+	"support_base_pattern_spacing": "2.5",
+	"support_speed": "150",
+	"support_threshold_angle": "30",
+	"support_object_xy_distance": "0.35",
+	"tree_support_branch_angle": "30",
+	"tree_support_wall_count": "0",
+	"detect_thin_wall": "0",
+	"top_surface_pattern": "monotonicline",
+	"top_shell_thickness": "0.8",
+	"enable_prime_tower": "1",
+	"wipe_tower_no_sparse_layers": "0",
+	"prime_tower_width": "60",
+	"xy_hole_compensation": "0",
+	"xy_contour_compensation": "0",
+	"layer_height": "0.2",
+	"bottom_shell_layers": "3",
+	"top_shell_layers": "4",
+	"bridge_flow": "1",
+	"initial_layer_speed": "45",
+	"initial_layer_infill_speed": "45",
+	"outer_wall_speed": "45",
+	"inner_wall_speed": "80",
+	"sparse_infill_speed": "150",
+	"internal_solid_infill_speed": "150",
+	"top_surface_speed": "50",
+	"gap_infill_speed": "30",
+	"travel_speed": "200"
+}
@@ -0,0 +1,54 @@
+{
+	"name": "Printcepts",
+	"version": "01.00.00.04",
+	"force_update": "0",
+	"description": "Printcepts belt printer configurations",
+	"machine_model_list": [
+		{
+			"name": "BabyBelt Pro",
+			"sub_path": "machine/BabyBelt Pro.json"
+		}
+	],
+	"process_list": [
+		{
+			"name": "fdm_process_common",
+			"sub_path": "process/fdm_process_common.json"
+		},
+		{
+			"name": "0.20mm Standard @BabyBelt Pro",
+			"sub_path": "process/0.20mm Standard @BabyBelt Pro.json"
+		}
+	],
+	"filament_list": [
+		{
+			"name": "Generic PLA @BabyBelt Pro",
+			"sub_path": "filament/Generic PLA @BabyBelt Pro.json"
+		},
+		{
+			"name": "eSUN PLA @BabyBelt Pro",
+			"sub_path": "filament/eSUN PLA @BabyBelt Pro.json"
+		},
+		{
+			"name": "Generic PETG @BabyBelt Pro",
+			"sub_path": "filament/Generic PETG @BabyBelt Pro.json"
+		}
+	],
+	"machine_list": [
+		{
+			"name": "fdm_machine_common",
+			"sub_path": "machine/fdm_machine_common.json"
+		},
+		{
+			"name": "fdm_klipper_common",
+			"sub_path": "machine/fdm_klipper_common.json"
+		},
+		{
+			"name": "fdm_belt_common",
+			"sub_path": "machine/fdm_belt_common.json"
+		},
+		{
+			"name": "BabyBelt Pro 0.4 nozzle",
+			"sub_path": "machine/BabyBelt Pro 0.4 nozzle.json"
+		}
+	]
+}
@@ -0,0 +1,70 @@
+<?xml version="1.0" encoding="UTF-8"?>
+<svg xmlns="http://www.w3.org/2000/svg" xmlns:xlink="http://www.w3.org/1999/xlink" width="95.0mm" height="500.0mm" viewBox="0 0 95.0 500.0" preserveAspectRatio="xMidYMid meet">
+  <!-- Printcepts BabyBelt Pro bed texture: 95 x 500 mm belt plate. -->
+  <!-- Transparent plate; green (#195F30) BabyBelt Pro logo centered along X, near the bottom edge. -->
+  <rect x="0" y="0" width="95.0" height="500.0" fill="none"/>
+  <g transform="translate(14.2500,436.3488) scale(0.067538)">
+    <g transform="translate(-11.000000,692.938562) scale(0.100000,-0.100000)"
+fill="#195F30" stroke="none">
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+</g>
+  </g>
+</svg>
@@ -0,0 +1,77 @@
+{
+	"type": "filament",
+	"name": "Generic PETG @BabyBelt Pro",
+	"inherits": "Generic PETG @System",
+	"from": "system",
+	"setting_id": "gCzHpDNgVwQR6tgk",
+	"instantiation": "true",
+	"filament_extruder_variant": [
+		"Direct Drive Standard"
+	],
+	"compatible_printers": [
+		"BabyBelt Pro 0.4 nozzle"
+	],
+	"filament_type": [
+		"PETG"
+	],
+	"filament_vendor": [
+		"Generic"
+	],
+	"filament_settings_id": [
+		"Generic PETG @BabyBelt Pro"
+	],
+	"filament_flow_ratio": [
+		"0.95"
+	],
+	"filament_cost": [
+		"25"
+	],
+	"nozzle_temperature": [
+		"240"
+	],
+	"nozzle_temperature_initial_layer": [
+		"245"
+	],
+	"cool_plate_temp": [
+		"80"
+	],
+	"cool_plate_temp_initial_layer": [
+		"80"
+	],
+	"fan_min_speed": [
+		"40"
+	],
+	"fan_max_speed": [
+		"60"
+	],
+	"overhang_fan_threshold": [
+		"25%"
+	],
+	"overhang_fan_speed": [
+		"80"
+	],
+	"full_fan_speed_layer": [
+		"8"
+	],
+	"slow_down_min_speed": [
+		"20"
+	],
+	"slow_down_layer_time": [
+		"4"
+	],
+	"fan_cooling_layer_time": [
+		"100"
+	],
+	"filament_retraction_length": [
+		"2"
+	],
+	"filament_retraction_speed": [
+		"40"
+	],
+	"filament_deretraction_speed": [
+		"40"
+	],
+	"filament_start_gcode": [
+		"; Generic PETG @BabyBelt Pro — belt PETG, bed 80C"
+	]
+}
@@ -0,0 +1,65 @@
+{
+	"type": "filament",
+	"name": "Generic PLA @BabyBelt Pro",
+	"inherits": "Generic PLA @System",
+	"from": "system",
+	"setting_id": "24PpcnhVx9v5f4fD",
+	"instantiation": "true",
+	"filament_extruder_variant": [
+		"Direct Drive Standard"
+	],
+	"compatible_printers": [
+		"BabyBelt Pro 0.4 nozzle"
+	],
+	"filament_type": [
+		"PLA"
+	],
+	"filament_vendor": [
+		"Generic"
+	],
+	"filament_settings_id": [
+		"Generic PLA @BabyBelt Pro"
+	],
+	"nozzle_temperature": [
+		"215"
+	],
+	"hot_plate_temp": [
+		"75"
+	],
+	"hot_plate_temp_initial_layer": [
+		"75"
+	],
+	"cool_plate_temp": [
+		"75"
+	],
+	"cool_plate_temp_initial_layer": [
+		"75"
+	],
+	"textured_plate_temp": [
+		"75"
+	],
+	"textured_plate_temp_initial_layer": [
+		"75"
+	],
+	"close_fan_the_first_x_layers": [
+		"3"
+	],
+	"full_fan_speed_layer": [
+		"8"
+	],
+	"slow_down_min_speed": [
+		"20"
+	],
+	"filament_retraction_length": [
+		"1.5"
+	],
+	"filament_retraction_speed": [
+		"35"
+	],
+	"filament_deretraction_speed": [
+		"30"
+	],
+	"filament_start_gcode": [
+		"; Generic PLA @BabyBelt Pro — belt PLA, bed 75C"
+	]
+}
@@ -0,0 +1,36 @@
+{
+	"type": "filament",
+	"name": "eSUN PLA @BabyBelt Pro",
+	"inherits": "Generic PLA @BabyBelt Pro",
+	"from": "system",
+	"setting_id": "EH3X7oE0DU5tSpjW",
+	"filament_id": "OFkrxQC4",
+	"instantiation": "true",
+	"compatible_printers": [
+		"BabyBelt Pro 0.4 nozzle"
+	],
+	"filament_type": [
+		"PLA"
+	],
+	"filament_vendor": [
+		"eSUN"
+	],
+	"filament_settings_id": [
+		"eSUN PLA @BabyBelt Pro"
+	],
+	"nozzle_temperature_initial_layer": [
+		"200"
+	],
+	"nozzle_temperature": [
+		"200"
+	],
+	"enable_pressure_advance": [
+		"1"
+	],
+	"pressure_advance": [
+		"0.12"
+	],
+	"filament_max_volumetric_speed": [
+		"20"
+	]
+}
@@ -0,0 +1,88 @@
+{
+	"type": "machine",
+	"name": "BabyBelt Pro 0.4 nozzle",
+	"inherits": "fdm_belt_common",
+	"from": "system",
+	"setting_id": "34OWINlJpJgA9DwQ",
+	"instantiation": "true",
+	"printer_model": "BabyBelt Pro",
+	"printer_variant": "0.4",
+	"nozzle_diameter": [
+		"0.4"
+	],
+	"default_filament_profile": [
+		"Generic PLA @BabyBelt Pro"
+	],
+	"default_print_profile": "0.20mm Standard @BabyBelt Pro",
+	"printable_area": [
+		"0x0",
+		"95x0",
+		"95x500",
+		"0x500"
+	],
+	"printable_height": "100",
+	"best_object_pos": "0.5,0.05",
+	"nozzle_type": [
+		"hardened_steel"
+	],
+	"printer_extruder_id": [
+		"1"
+	],
+	"printer_extruder_variant": [
+		"Direct Drive Standard"
+	],
+	"thumbnails": [
+		"48x48/PNG",
+		"300x300/PNG"
+	],
+	"machine_max_acceleration_e": [
+		"500",
+		"5000"
+	],
+	"machine_max_acceleration_extruding": [
+		"500",
+		"20000"
+	],
+	"machine_max_acceleration_retracting": [
+		"500",
+		"5000"
+	],
+	"machine_max_acceleration_x": [
+		"500",
+		"20000"
+	],
+	"machine_max_acceleration_y": [
+		"500",
+		"20000"
+	],
+	"machine_max_junction_deviation": [
+		"0.01",
+		"0.01"
+	],
+	"machine_max_speed_x": [
+		"50",
+		"200"
+	],
+	"machine_max_speed_y": [
+		"50",
+		"200"
+	],
+	"machine_max_speed_z": [
+		"5",
+		"12"
+	],
+	"retraction_length": [
+		"1.5"
+	],
+	"retraction_speed": [
+		"20"
+	],
+	"deretraction_speed": [
+		"25"
+	],
+	"retract_lift_enforce": [
+		"Top and Bottom"
+	],
+	"support_chamber_temp_control": "0",
+	"machine_start_gcode": ";Start GCode\nPRINT_START ANGLE=[belt_slice_rotation_angle] EXTRUDER=[nozzle_temperature_initial_layer] BED=[hot_plate_temp_initial_layer] MATERIAL=[filament_type]\n"
+}
@@ -0,0 +1,12 @@
+{
+	"type": "machine_model",
+	"name": "BabyBelt Pro",
+	"model_id": "Printcepts_BabyBelt_Pro",
+	"nozzle_diameter": "0.4",
+	"machine_tech": "FFF",
+	"family": "Printcepts",
+	"bed_model": "",
+	"bed_texture": "BabyBelt Pro_bed_texture.svg",
+	"hotend_model": "",
+	"default_materials": "Generic PLA @BabyBelt Pro;Generic PETG @BabyBelt Pro"
+}
@@ -0,0 +1,99 @@
+{
+	"type": "machine",
+	"name": "fdm_belt_common",
+	"inherits": "fdm_klipper_common",
+	"from": "system",
+	"instantiation": "false",
+	"gcode_flavor": "klipper",
+	"single_extruder_multi_material": "0",
+	"default_filament_profile": [
+		"Generic PLA @System"
+	],
+	"default_print_profile": "0.20mm Standard @BabyBelt Pro",
+	"max_layer_height": [
+		"0.32"
+	],
+	"min_layer_height": [
+		"0.08"
+	],
+	"deretraction_speed": [
+		"30"
+	],
+	"extruder_colour": [
+		"#FCE94F"
+	],
+	"extruder_offset": [
+		"0x0"
+	],
+	"long_retractions_when_cut": [
+		"0"
+	],
+	"nozzle_diameter": [
+		"0.4"
+	],
+	"retract_before_wipe": [
+		"70%"
+	],
+	"retract_length_toolchange": [
+		"2"
+	],
+	"retract_lift_above": [
+		"0"
+	],
+	"retract_lift_below": [
+		"0"
+	],
+	"retract_lift_enforce": [
+		"All Surfaces"
+	],
+	"retract_restart_extra": [
+		"0"
+	],
+	"retract_restart_extra_toolchange": [
+		"0"
+	],
+	"retract_when_changing_layer": [
+		"1"
+	],
+	"retraction_distances_when_cut": [
+		"18"
+	],
+	"retraction_length": [
+		"0.8"
+	],
+	"retraction_minimum_travel": [
+		"1"
+	],
+	"retraction_speed": [
+		"30"
+	],
+	"travel_slope": [
+		"3"
+	],
+	"wipe": [
+		"1"
+	],
+	"wipe_distance": [
+		"1"
+	],
+	"z_hop": [
+		"0"
+	],
+	"z_hop_types": [
+		"Normal Lift"
+	],
+	"gcode_remap_x": "rev_x",
+	"gcode_remap_y": "pos_z",
+	"gcode_remap_z": "pos_y",
+	"printer_extruder_id": [
+		"1"
+	],
+	"belt_printer": "1",
+	"belt_slice_rotation": "x",
+	"belt_slice_rotation_angle": "45",
+	"belt_slice_rotation_global": "1",
+	"build_plate_tilt_x": "45",
+	"purge_in_prime_tower": "0",
+	"scan_first_layer": "0",
+	"auxiliary_fan": "0"
+}
@@ -0,0 +1,140 @@
+{
+	"type": "machine",
+	"name": "fdm_klipper_common",
+	"inherits": "fdm_machine_common",
+	"from": "system",
+	"instantiation": "false",
+	"gcode_flavor": "klipper",
+	"machine_max_acceleration_e": [
+		"5000",
+		"5000"
+	],
+	"machine_max_acceleration_extruding": [
+		"20000",
+		"20000"
+	],
+	"machine_max_acceleration_retracting": [
+		"5000",
+		"5000"
+	],
+	"machine_max_acceleration_travel": [
+		"20000",
+		"20000"
+	],
+	"machine_max_acceleration_x": [
+		"20000",
+		"20000"
+	],
+	"machine_max_acceleration_y": [
+		"20000",
+		"20000"
+	],
+	"machine_max_acceleration_z": [
+		"500",
+		"200"
+	],
+	"machine_max_speed_e": [
+		"25",
+		"25"
+	],
+	"machine_max_speed_x": [
+		"500",
+		"200"
+	],
+	"machine_max_speed_y": [
+		"500",
+		"200"
+	],
+	"machine_max_speed_z": [
+		"12",
+		"12"
+	],
+	"machine_max_jerk_e": [
+		"2.5",
+		"2.5"
+	],
+	"machine_max_jerk_x": [
+		"9",
+		"9"
+	],
+	"machine_max_jerk_y": [
+		"9",
+		"9"
+	],
+	"machine_max_jerk_z": [
+		"0.2",
+		"0.4"
+	],
+	"machine_min_extruding_rate": [
+		"0",
+		"0"
+	],
+	"machine_min_travel_rate": [
+		"0",
+		"0"
+	],
+	"max_layer_height": [
+		"0.32"
+	],
+	"min_layer_height": [
+		"0.08"
+	],
+	"printable_height": "250",
+	"extruder_clearance_radius": "65",
+	"extruder_clearance_height_to_rod": "36",
+	"extruder_clearance_height_to_lid": "140",
+	"printer_settings_id": "",
+	"printer_technology": "FFF",
+	"printer_variant": "0.4",
+	"retraction_minimum_travel": [
+		"1"
+	],
+	"retract_before_wipe": [
+		"70%"
+	],
+	"retract_when_changing_layer": [
+		"1"
+	],
+	"retraction_length": [
+		"0.8"
+	],
+	"retract_length_toolchange": [
+		"2"
+	],
+	"z_hop": [
+		"0.4"
+	],
+	"retract_restart_extra": [
+		"0"
+	],
+	"retract_restart_extra_toolchange": [
+		"0"
+	],
+	"retraction_speed": [
+		"30"
+	],
+	"deretraction_speed": [
+		"30"
+	],
+	"z_hop_types": "Normal Lift",
+	"single_extruder_multi_material": "1",
+	"change_filament_gcode": "",
+	"wipe": [
+		"1"
+	],
+	"default_filament_profile": [
+		"Generic PLA @System"
+	],
+	"default_print_profile": "0.20mm Standard @MyKlipper",
+	"bed_exclude_area": [
+		"0x0"
+	],
+	"machine_start_gcode": "M190 S[bed_temperature_initial_layer_single]\nM109 S[nozzle_temperature_initial_layer]\nPRINT_START EXTRUDER=[nozzle_temperature_initial_layer] BED=[bed_temperature_initial_layer_single]\n",
+	"machine_end_gcode": "PRINT_END",
+	"layer_change_gcode": ";AFTER_LAYER_CHANGE\n;[layer_z]",
+	"before_layer_change_gcode": ";BEFORE_LAYER_CHANGE\n;[layer_z]\nG92 E0\n",
+	"machine_pause_gcode": "PAUSE",
+	"scan_first_layer": "0",
+	"nozzle_type": "undefine",
+	"auxiliary_fan": "0"
+}
@@ -0,0 +1,118 @@
+{
+	"type": "machine",
+	"name": "fdm_machine_common",
+	"from": "system",
+	"instantiation": "false",
+	"printer_technology": "FFF",
+	"deretraction_speed": [
+		"40"
+	],
+	"extruder_colour": [
+		"#FCE94F"
+	],
+	"extruder_offset": [
+		"0x0"
+	],
+	"gcode_flavor": "marlin",
+	"machine_max_acceleration_e": [
+		"5000"
+	],
+	"machine_max_acceleration_extruding": [
+		"10000"
+	],
+	"machine_max_acceleration_retracting": [
+		"1000"
+	],
+	"machine_max_acceleration_x": [
+		"10000"
+	],
+	"machine_max_acceleration_y": [
+		"10000"
+	],
+	"machine_max_acceleration_z": [
+		"500"
+	],
+	"machine_max_speed_e": [
+		"60"
+	],
+	"machine_max_speed_x": [
+		"500"
+	],
+	"machine_max_speed_y": [
+		"500"
+	],
+	"machine_max_speed_z": [
+		"10"
+	],
+	"machine_max_jerk_e": [
+		"5"
+	],
+	"machine_max_jerk_x": [
+		"8"
+	],
+	"machine_max_jerk_y": [
+		"8"
+	],
+	"machine_max_jerk_z": [
+		"0.4"
+	],
+	"machine_min_extruding_rate": [
+		"0"
+	],
+	"machine_min_travel_rate": [
+		"0"
+	],
+	"max_layer_height": [
+		"0.32"
+	],
+	"min_layer_height": [
+		"0.08"
+	],
+	"printable_height": "250",
+	"extruder_clearance_radius": "65",
+	"extruder_clearance_height_to_rod": "36",
+	"extruder_clearance_height_to_lid": "140",
+	"nozzle_diameter": [
+		"0.4"
+	],
+	"printer_settings_id": "",
+	"printer_variant": "0.4",
+	"retraction_minimum_travel": [
+		"2"
+	],
+	"retract_before_wipe": [
+		"70%"
+	],
+	"retract_when_changing_layer": [
+		"1"
+	],
+	"retraction_length": [
+		"1"
+	],
+	"retract_length_toolchange": [
+		"1"
+	],
+	"z_hop": [
+		"0"
+	],
+	"retract_restart_extra": [
+		"0"
+	],
+	"retract_restart_extra_toolchange": [
+		"0"
+	],
+	"retraction_speed": [
+		"60"
+	],
+	"single_extruder_multi_material": "1",
+	"change_filament_gcode": "",
+	"wipe": [
+		"1"
+	],
+	"default_print_profile": "",
+	"machine_start_gcode": "G0 Z20 F9000\nG92 E0; G1 E-10 F1200\nG28\nM970 Q1 A10 B10 C130 K0\nM970 Q1 A10 B131 C250 K1\nM974 Q1 S1 P0\nM970 Q0 A10 B10 C130 H20 K0\nM970 Q0 A10 B131 C250 K1\nM974 Q0 S1 P0\nM220 S100 ;Reset Feedrate\nM221 S100 ;Reset Flowrate\nG29 ;Home\nG90;\nG92 E0 ;Reset Extruder \nG1 Z2.0 F3000 ;Move Z Axis up \nG1 X10.1 Y20 Z0.28 F5000.0 ;Move to start position\nM109 S205;\nG1 X10.1 Y200.0 Z0.28 F1500.0 E15 ;Draw the first line\nG1 X10.4 Y200.0 Z0.28 F5000.0 ;Move to side a little\nG1 X10.4 Y20 Z0.28 F1500.0 E30 ;Draw the second line\nG92 E0 ;Reset Extruder \nG1 X110 Y110 Z2.0 F3000 ;Move Z Axis up",
+	"machine_end_gcode": "M400 ; wait for buffer to clear\nG92 E0 ; zero the extruder\nG1 E-4.0 F3600; retract \nG91\nG1 Z3;\nM104 S0 ; turn off hotend\nM140 S0 ; turn off bed\nM106 S0 ; turn off fan\nG90 \nG0 X110 Y200 F3600 \nprint_end",
+	"layer_change_gcode": ";AFTER_LAYER_CHANGE\n;[layer_z]",
+	"before_layer_change_gcode": ";BEFORE_LAYER_CHANGE\n;[layer_z]\nG92 E0\n",
+	"machine_pause_gcode": "M601"
+}
@@ -0,0 +1,23 @@
+{
+	"type": "process",
+	"name": "0.20mm Standard @BabyBelt Pro",
+	"inherits": "fdm_process_common",
+	"from": "system",
+	"setting_id": "JGfGtqX6CWjCt437",
+	"instantiation": "true",
+	"layer_height": "0.2",
+	"initial_layer_print_height": "0.2",
+	"initial_layer_line_width": "0.42",
+	"wall_loops": "2",
+	"reduce_infill_retraction": "1",
+	"detect_overhang_wall": "1",
+	"skirt_loops": "0",
+	"skirt_distance": "0",
+	"sparse_infill_pattern": "grid",
+	"sparse_infill_speed": "200",
+	"support_base_pattern": "rectilinear",
+	"support_interface_pattern": "rectilinear",
+	"compatible_printers": [
+		"BabyBelt Pro 0.4 nozzle"
+	]
+}
@@ -0,0 +1,106 @@
+{
+	"type": "process",
+	"name": "fdm_process_common",
+	"from": "system",
+	"instantiation": "false",
+	"reduce_crossing_wall": "0",
+	"max_travel_detour_distance": "0",
+	"bottom_surface_pattern": "monotonic",
+	"bottom_shell_thickness": "0",
+	"bridge_speed": "50",
+	"brim_width": "5",
+	"brim_object_gap": "0.1",
+	"compatible_printers": [],
+	"compatible_printers_condition": "",
+	"print_sequence": "by layer",
+	"default_acceleration": "1000",
+	"initial_layer_acceleration": "500",
+	"top_surface_acceleration": "1000",
+	"travel_acceleration": "1000",
+	"inner_wall_acceleration": "1000",
+	"outer_wall_acceleration": "700",
+	"bridge_no_support": "0",
+	"draft_shield": "disabled",
+	"elefant_foot_compensation": "0",
+	"enable_arc_fitting": "0",
+	"wall_infill_order": "inner wall/outer wall/infill",
+	"infill_direction": "45",
+	"sparse_infill_density": "15%",
+	"sparse_infill_pattern": "crosshatch",
+	"initial_layer_print_height": "0.2",
+	"infill_combination": "0",
+	"infill_wall_overlap": "25%",
+	"interface_shells": "0",
+	"ironing_flow": "10%",
+	"ironing_spacing": "0.15",
+	"ironing_speed": "30",
+	"ironing_type": "no ironing",
+	"reduce_infill_retraction": "1",
+	"filename_format": "{input_filename_base}_{layer_height}mm_{filament_type[initial_tool]}_{printer_model}_{print_time}.gcode",
+	"detect_overhang_wall": "1",
+	"slowdown_for_curled_perimeters": "1",
+	"overhang_1_4_speed": "0",
+	"overhang_2_4_speed": "50",
+	"overhang_3_4_speed": "30",
+	"overhang_4_4_speed": "10",
+	"line_width": "110%",
+	"inner_wall_line_width": "110%",
+	"outer_wall_line_width": "100%",
+	"top_surface_line_width": "93.75%",
+	"sparse_infill_line_width": "110%",
+	"initial_layer_line_width": "120%",
+	"internal_solid_infill_line_width": "120%",
+	"support_line_width": "96%",
+	"wall_loops": "3",
+	"print_settings_id": "",
+	"raft_layers": "0",
+	"seam_position": "aligned",
+	"skirt_distance": "2",
+	"skirt_height": "3",
+	"min_skirt_length": "4",
+	"skirt_loops": "0",
+	"minimum_sparse_infill_area": "15",
+	"spiral_mode": "0",
+	"standby_temperature_delta": "-5",
+	"enable_support": "0",
+	"resolution": "0.012",
+	"support_type": "normal(auto)",
+	"support_on_build_plate_only": "0",
+	"support_top_z_distance": "0.2",
+	"support_bottom_z_distance": "0.2",
+	"support_filament": "0",
+	"support_interface_loop_pattern": "0",
+	"support_interface_filament": "0",
+	"support_interface_top_layers": "2",
+	"support_interface_bottom_layers": "2",
+	"support_interface_spacing": "0.5",
+	"support_interface_speed": "80",
+	"support_base_pattern": "default",
+	"support_base_pattern_spacing": "2.5",
+	"support_speed": "150",
+	"support_threshold_angle": "30",
+	"support_object_xy_distance": "0.35",
+	"tree_support_branch_angle": "30",
+	"tree_support_wall_count": "0",
+	"detect_thin_wall": "0",
+	"top_surface_pattern": "monotonicline",
+	"top_shell_thickness": "0.8",
+	"enable_prime_tower": "1",
+	"wipe_tower_no_sparse_layers": "0",
+	"prime_tower_width": "60",
+	"xy_hole_compensation": "0",
+	"xy_contour_compensation": "0",
+	"layer_height": "0.2",
+	"bottom_shell_layers": "3",
+	"top_shell_layers": "4",
+	"bridge_flow": "1",
+	"initial_layer_speed": "45",
+	"initial_layer_infill_speed": "45",
+	"outer_wall_speed": "45",
+	"inner_wall_speed": "80",
+	"sparse_infill_speed": "150",
+	"internal_solid_infill_speed": "150",
+	"top_surface_speed": "50",
+	"gap_infill_speed": "30",
+	"travel_speed": "200"
+}
@@ -26,6 +26,7 @@ struct SlopeDetection
    bool actived;
 	float normal_z;
    mat3 volume_world_normal_matrix;
+    vec3 up_direction;
 };

 uniform vec4 uniform_color;
@@ -23,6 +23,7 @@ struct SlopeDetection
    bool actived;
 	float normal_z;
    mat3 volume_world_normal_matrix;
+    vec3 up_direction;
 };

 uniform mat4 view_model_matrix;
@@ -77,8 +78,8 @@ void main()
    // Point in homogenous coordinates.
    world_pos = volume_world_matrix * vec4(v_position, 1.0);

-    // z component of normal vector in world coordinate used for slope shading
-    world_normal_z = slope.actived ? (normalize(slope.volume_world_normal_matrix * v_normal)).z : 0.0;
+    // dot product of world normal with up direction, used for slope shading
+    world_normal_z = slope.actived ? dot(normalize(slope.volume_world_normal_matrix * v_normal), slope.up_direction) : 0.0;

    gl_Position = projection_matrix * position;
    if (is_outline) {
@@ -37,6 +37,7 @@ struct SlopeDetection
    bool actived;
 	 float normal_z;
    mat3 volume_world_normal_matrix;
+    vec3 up_direction;
 };
 uniform SlopeDetection slope;

@@ -85,7 +86,7 @@ void main()
              color = LightBlue;
              alpha = 1.0;
         }
-         else if( transformed_normal.z < slope.normal_z - EPSILON)
+         else if( dot(transformed_normal, slope.up_direction) < slope.normal_z - EPSILON)
        {
            color = color * 0.5 + LightRed * 0.5;
            alpha = 1.0;
@@ -24,6 +24,7 @@ struct SlopeDetection
    bool actived;
 	float normal_z;
    mat3 volume_world_normal_matrix;
+    vec3 up_direction;
 };
 uniform SlopeDetection slope;
 void main()
@@ -7,6 +7,7 @@ struct SlopeDetection
    bool actived;
    float normal_z;
    mat3 volume_world_normal_matrix;
+    vec3 up_direction;
 };

 uniform mat4 view_model_matrix;
@@ -46,8 +47,8 @@ void main()
    // Point in homogenous coordinates.
    world_pos = volume_world_matrix * vec4(v_position, 1.0);

-    // z component of normal vector in world coordinate used for slope shading
-    world_normal_z = slope.actived ? (normalize(slope.volume_world_normal_matrix * v_normal)).z : 0.0;
+    // dot product of world normal with up direction, used for slope shading
+    world_normal_z = slope.actived ? dot(normalize(slope.volume_world_normal_matrix * v_normal), slope.up_direction) : 0.0;

    gl_Position = projection_matrix * position;
    if (is_outline) {
@@ -29,6 +29,7 @@ struct SlopeDetection
    bool actived;
 	float normal_z;
    mat3 volume_world_normal_matrix;
+    vec3 up_direction;
 };

 uniform vec4 uniform_color;
@@ -23,6 +23,7 @@ struct SlopeDetection
    bool actived;
 	float normal_z;
    mat3 volume_world_normal_matrix;
+    vec3 up_direction;
 };

 uniform mat4 view_model_matrix;
@@ -77,8 +78,8 @@ void main()
    // Point in homogenous coordinates.
    world_pos = volume_world_matrix * vec4(v_position, 1.0);

-    // z component of normal vector in world coordinate used for slope shading
-    world_normal_z = slope.actived ? (normalize(slope.volume_world_normal_matrix * v_normal)).z : 0.0;
+    // dot product of world normal with up direction, used for slope shading
+    world_normal_z = slope.actived ? dot(normalize(slope.volume_world_normal_matrix * v_normal), slope.up_direction) : 0.0;

    gl_Position = projection_matrix * position;
    if (is_outline) {
@@ -37,6 +37,7 @@ struct SlopeDetection
    bool actived;
 	 float normal_z;
    mat3 volume_world_normal_matrix;
+    vec3 up_direction;
 };
 uniform SlopeDetection slope;

@@ -87,7 +88,7 @@ void main()
              color = LightBlue;
              alpha = 1.0;
         }
-         else if( transformed_normal.z < slope.normal_z - EPSILON)
+         else if( dot(transformed_normal, slope.up_direction) < slope.normal_z - EPSILON)
        {
            color = color * 0.5 + LightRed * 0.5;
            alpha = 1.0;
@@ -24,6 +24,7 @@ struct SlopeDetection
    bool actived;
 	float normal_z;
    mat3 volume_world_normal_matrix;
+    vec3 up_direction;
 };
 uniform SlopeDetection slope;
 void main()
@@ -7,6 +7,7 @@ struct SlopeDetection
    bool actived;
    float normal_z;
    mat3 volume_world_normal_matrix;
+    vec3 up_direction;
 };

 uniform mat4 view_model_matrix;
@@ -46,8 +47,8 @@ void main()
    // Point in homogenous coordinates.
    world_pos = volume_world_matrix * vec4(v_position, 1.0);

-    // z component of normal vector in world coordinate used for slope shading
-    world_normal_z = slope.actived ? (normalize(slope.volume_world_normal_matrix * v_normal)).z : 0.0;
+    // dot product of world normal with up direction, used for slope shading
+    world_normal_z = slope.actived ? dot(normalize(slope.volume_world_normal_matrix * v_normal), slope.up_direction) : 0.0;

    gl_Position = projection_matrix * position;
    if (is_outline) {
@@ -8,9 +8,6 @@ include) fails wherever the error is. Headers are compiled on their own, and
 fail only on errors in their changed lines. Deleting an #include also fails
 on every use, changed or not, that now lacks the header it provided.

-With -- --fix, clang-tidy adds the missing includes, on those lines only, and
-each file it changed is checked again so that only what remains is reported.
-
 The checks come from .clang-tidy at the repository root. The compile database
 must come from a configure with SLIC3R_PCH=OFF, or the precompiled header hides
 missing includes.
@@ -105,10 +102,9 @@ def is_checked(path):

 def changed_files(merge_base):
    # Against the working tree, so a local run covers uncommitted edits too.
-    # core.quotePath=false keeps a non-ASCII path unquoted, and the explicit prefixes
-    # override diff.noprefix and diff.mnemonicPrefix, so parse_diff sees its b/ prefix.
+    # core.quotePath=false keeps a non-ASCII path unquoted, so parse_diff sees its b/ prefix.
    diff = subprocess.run(["git", "-c", "core.quotePath=false", "diff", "-U0", "--no-color", "--no-ext-diff",
-                           "--src-prefix=a/", "--dst-prefix=b/", "--diff-filter=AMR", merge_base],
+                           "--diff-filter=AMR", merge_base],
                          check=True, capture_output=True, **UTF8).stdout
    return {path: change for path, change in parse_diff(diff).items() if is_checked(path)}

@@ -205,19 +201,13 @@ def errors_alone_at(revision, clang_tidy, build_dir, path):


 def check_file(clang_tidy, build_dir, merge_base, path, change, extra_args):
-    """Run clang-tidy on one file and return (failed, output, failing diagnostics, fixed)."""
-    fixing = any(arg.startswith("--fix") for arg in extra_args)
-    if fixing:
-        with open(path, "rb") as f:
-            before = f.read()
+    """Run clang-tidy on one file and return (failed, output, failing diagnostics)."""
    # A deleted include can orphan uses on unchanged lines, so such a file is
-    # checked whole and the findings narrowed here. --fix keeps a line filter so
-    # it never rewrites unrelated code, which for such a file means a second,
-    # fixing run limited to the lines the first one found wanting.
-    whole = bool(change.removed_includes)
+    # checked whole and the findings narrowed here. --fix keeps the line filter
+    # so it never rewrites unrelated code.
+    whole = bool(change.removed_includes) and not extra_args
    returncode, output, diagnostics = run_clang_tidy(clang_tidy, build_dir, path,
-                                                     None if whole else change.lines,
-                                                     [] if whole else extra_args)
+                                                     None if whole else change.lines, extra_args)
    real = os.path.realpath(path)

    def introduced(d):
@@ -233,25 +223,14 @@ def check_file(clang_tidy, build_dir, merge_base, path, change, extra_args):
        if errors and change.removed_includes:
            with open(path, encoding="utf-8") as f:
                text = f.read()
-            before_sites = errors_alone_at(merge_base, clang_tidy, build_dir, path)
+            before = errors_alone_at(merge_base, clang_tidy, build_dir, path)
            failing += [d for d in errors if d not in failing
-                        and (error_sites([d], text) - before_sites)]
-        failed = bool(failing)
-    elif whole:
+                        and (error_sites([d], text) - before)]
+        return bool(failing), output, failing
+    if whole:
        failing = [d for d in diagnostics if d.is_compile_error or introduced(d)]
-        failed = bool(failing)
-    else:
-        failing, failed = diagnostics, returncode != 0
-    if not fixing:
-        return failed, output, failing, False
-    if whole and failing:
-        lines = change.lines + [[d.line, d.line] for d in failing if os.path.realpath(d.file) == real]
-        run_clang_tidy(clang_tidy, build_dir, path, lines, extra_args)
-    with open(path, "rb") as f:
-        if f.read() == before:
-            return failed, output, failing, False
-    # Checked again, so what is reported is what the fixes left.
-    return check_file(clang_tidy, build_dir, merge_base, path, change, [])[:3] + (True,)
+        return bool(failing), output, failing
+    return returncode != 0, output, diagnostics


 def main():
@@ -284,14 +263,11 @@ def main():
    annotate = os.environ.get("GITHUB_ACTIONS") == "true"
    root = os.getcwd() + os.sep
    failed = []
-    fixed = []
    with ThreadPoolExecutor(max_workers=args.jobs) as pool:
        jobs = {path: pool.submit(check_file, args.clang_tidy, args.build_dir, merge_base, path, change, args.extra_args)
                for path, change in todo}
        for path, job in jobs.items():
-            file_failed, output, diagnostics, file_fixed = job.result()
-            if file_fixed:
-                fixed.append(path)
+            file_failed, output, diagnostics = job.result()
            if not file_failed:
                continue
            failed.append(path)
@@ -306,13 +282,6 @@ def main():
            if len(diagnostics) > MAX_REPORTED:
                print(f"... and {len(diagnostics) - MAX_REPORTED} more")

-    if fixed:
-        print(f"\nAdded includes to {len(fixed)} file(s):")
-        for path in fixed:
-            print(f"    {path}")
-    if failed and fixed:
-        print(f"\nclang-tidy still fails on {len(failed)} file(s); the findings above are what --fix could not add.")
-        return 1
    if failed:
        print(f"\nclang-tidy failed on {len(failed)} file(s). Add the includes it names, or apply its "
              "suggestions locally with scripts/run_clang_tidy.sh --fix (scripts\\run_clang_tidy.ps1 -Fix on Windows).")
@@ -6,9 +6,8 @@
 #   scripts/run_clang_tidy.sh --fix      also add the missing includes it names
 #
 # It configures a separate build directory (build-tidy) without the precompiled
-# header, uses the clang-tidy on your system or installs the pinned one into a
-# virtual environment inside it, and runs scripts/clang_tidy_diff.py the way CI
-# does. Uncommitted changes are checked too.
+# header, installs the pinned clang-tidy into a virtual environment inside it, and
+# runs scripts/clang_tidy_diff.py the way CI does. Uncommitted changes are checked too.

 set -euo pipefail

@@ -24,8 +23,7 @@ Usage: scripts/run_clang_tidy.sh [options]
                       deps/build/<arch> on macOS)
  -j, --jobs N         parallel clang-tidy runs (default: all cores)
      --fix            apply clang-tidy's fixes (adds the missing includes)
-  -y, --yes            install missing tools without asking; another clang-tidy
-                       version found on the system is then not offered
+  -y, --yes            install missing tools without asking
  -h, --help           show this help
 EOF
 }
@@ -138,38 +136,12 @@ REQUIREMENTS="$ROOT/scripts/clang_tidy_requirements.txt"
 PINNED=$(sed -n 's/^clang-tidy==//p' "$REQUIREMENTS")
 VENV="$BUILD_DIR/clang-tidy-venv"

-is_pinned() {
-    [ -x "$1" ] && "$1" --version 2>/dev/null | grep -q "version $PINNED"
-}
-
-CLANG_TIDY="${CLANG_TIDY:-}"
-if [ -n "$CLANG_TIDY" ]; then
+if [ -n "${CLANG_TIDY:-}" ]; then
    # Set by the caller: use it as is.
-    is_pinned "$CLANG_TIDY" || echo "Warning: $CLANG_TIDY is not clang-tidy $PINNED, so results may differ from CI." >&2
+    :
 else
-    # One already on the system comes first: the pinned version outright, another
-    # version if the user accepts the difference. The pinned version is installed
-    # into a virtual environment otherwise.
-    INSTALLED=""
-    for candidate in $(command -v clang-tidy "clang-tidy-${PINNED%%.*}" || true) \
-                     "/usr/lib/llvm-${PINNED%%.*}/bin/clang-tidy" \
-                     "$(brew --prefix llvm 2>/dev/null || true)/bin/clang-tidy"; do
-        if is_pinned "$candidate"; then
-            CLANG_TIDY="$candidate"
-            break
-        fi
-        [ -z "$INSTALLED" ] && [ -x "$candidate" ] && INSTALLED="$candidate"
-    done
-    if [ -z "$CLANG_TIDY" ] && [ -n "$INSTALLED" ] && [ "$YES" = 0 ] && ! is_pinned "$VENV/bin/clang-tidy"; then
-        echo "Found $INSTALLED, which is $("$INSTALLED" --version | sed -n 's/.*version \([0-9.]*\).*/\1/p' | head -n 1), not the $PINNED CI uses, so results may differ slightly."
-        if ask "Use it anyway?"; then
-            CLANG_TIDY="$INSTALLED"
-        fi
-    fi
-fi
-if [ -z "$CLANG_TIDY" ]; then
    CLANG_TIDY="$VENV/bin/clang-tidy"
-    if ! is_pinned "$CLANG_TIDY"; then
+    if [ ! -x "$CLANG_TIDY" ] || ! "$CLANG_TIDY" --version | grep -q "version $PINNED"; then
        if ask "clang-tidy $PINNED (the version CI uses) is not installed. Install it into $VENV?"; then
            mkdir -p "$BUILD_DIR"
            if ! python3 -m venv "$VENV"; then
@@ -186,6 +158,9 @@ if [ -z "$CLANG_TIDY" ]; then
        fi
    fi
 fi
+if ! "$CLANG_TIDY" --version | grep -q "version $PINNED"; then
+    echo "Warning: $CLANG_TIDY is not clang-tidy $PINNED, so results may differ from CI." >&2
+fi

 # --- Dependencies -------------------------------------------------------------

@@ -242,12 +217,7 @@ cmake --build "$BUILD_DIR" --target git_commit_hash_header >/dev/null

 if [ -z "$BASE" ]; then
    REMOTE=$(git remote -v | awk '/github\.com[:\/]OrcaSlicer\/OrcaSlicer(\.git)? \(fetch\)/ { print $1; exit }')
-    if [ -z "$REMOTE" ]; then
-        # Against a fork's main that already has the commits, nothing is checked.
-        echo "Warning: no remote points at github.com/OrcaSlicer/OrcaSlicer, so this compares against origin/main." >&2
-        echo "If origin is your fork, add the upstream remote (git remote add upstream https://github.com/OrcaSlicer/OrcaSlicer.git) or pass --base." >&2
-        REMOTE=origin
-    fi
+    REMOTE="${REMOTE:-origin}"
    if [ "$FETCH" = 1 ]; then
        git fetch --quiet "$REMOTE" main
    fi
@@ -155,8 +155,6 @@ class TestSubprocessCalls(unittest.TestCase):
        diff = "+++ b/src/libslic3r/Über.cpp\n@@ -1,0 +2 @@\n+// 打印\n"
        files, call, _ = self.run_patched(clang_tidy_diff.changed_files, "base", stdout=diff)
        self.assertIn("core.quotePath=false", call.args[0])
-        # Whatever diff.noprefix or diff.mnemonicPrefix a user has set.
-        self.assertIn("--dst-prefix=b/", call.args[0])
        self.assertEqual(call.kwargs["encoding"], "utf-8")
        self.assertEqual(files["src/libslic3r/Über.cpp"].lines, [[2, 2]])

@@ -169,60 +167,5 @@ class TestSubprocessCalls(unittest.TestCase):
        self.assertEqual(call.kwargs["encoding"], "utf-8")


-class TestCheckFileFix(unittest.TestCase):
-    """check_file with -- --fix: what clang-tidy is run on, and what is reported afterwards."""
-
-    def setUp(self):
-        self.dir = tempfile.TemporaryDirectory()
-        self.addCleanup(self.dir.cleanup)
-        self.path = os.path.join(self.dir.name, "Color.cpp")
-        with open(self.path, "w") as f:
-            f.write("int x;\n")
-
-    def finding(self, line, include=""):
-        return clang_tidy_diff.Diagnostic(self.path, line, 1, "error",
-                                          'no header providing "x" is directly included [misc-include-cleaner]', include)
-
-    def check(self, change, results, fix_writes=None):
-        """Run check_file with run_clang_tidy answering from `results` in turn; the --fix run
-        rewrites the file with `fix_writes` when given. Returns (result, calls)."""
-        calls = []
-
-        def run(clang_tidy, build_dir, path, lines, extra_args):
-            calls.append((lines, extra_args))
-            if "--fix" in extra_args and fix_writes is not None:
-                with open(path, "w") as f:
-                    f.write(fix_writes)
-            return results[len(calls) - 1]
-
-        with mock.patch.object(clang_tidy_diff, "run_clang_tidy", side_effect=run):
-            result = clang_tidy_diff.check_file("clang-tidy", "build", "base", self.path, change, ["--fix"])
-        return result, calls
-
-    def test_a_deleted_include_is_fixed_on_the_lines_it_orphaned_only(self):
-        change = clang_tidy_diff.FileChange(lines=[[4, 4]], removed_includes={"libslic3r/Point.hpp"})
-        orphaned = self.finding(50, "<libslic3r/Point.hpp>")
-        unrelated = self.finding(60, "<vector>")
-        (failed, _, failing, fixed), calls = self.check(
-            change, [(1, "", [orphaned, unrelated]), (1, "", [orphaned]), (0, "", [])], fix_writes="#include <libslic3r/Point.hpp>\n")
-        self.assertEqual(calls, [(None, []), ([[4, 4], [50, 50]], ["--fix"]), (None, [])])
-        self.assertEqual((failed, failing, fixed), (False, [], True))
-
-    def test_a_file_the_fix_did_not_change_keeps_its_findings(self):
-        change = clang_tidy_diff.FileChange(lines=[[4, 4]])
-        error = clang_tidy_diff.Diagnostic(self.path, 4, 1, "error", "unknown type name 'Foo' [clang-diagnostic-error]")
-        (failed, _, failing, fixed), calls = self.check(change, [(1, "", [error])])
-        self.assertEqual(calls, [([[4, 4]], ["--fix"])])
-        self.assertEqual((failed, failing, fixed), (True, [error], False))
-
-    def test_a_changed_file_is_checked_again_and_reports_what_is_left(self):
-        change = clang_tidy_diff.FileChange(lines=[[4, 4]])
-        error = clang_tidy_diff.Diagnostic(self.path, 4, 1, "error", "unknown type name 'Foo' [clang-diagnostic-error]")
-        (failed, _, failing, fixed), calls = self.check(
-            change, [(1, "", [self.finding(4, "<vector>"), error]), (1, "", [error])], fix_writes="#include <vector>\n")
-        self.assertEqual(calls, [([[4, 4]], ["--fix"]), ([[4, 4]], [])])
-        self.assertEqual((failed, failing, fixed), (True, [error], True))
-
-
 if __name__ == "__main__":
    unittest.main()
@@ -91,6 +91,12 @@ if (SLIC3R_GUI)
 #    list(REMOVE_ITEM wxWidgets_LIBRARIES oleacc)

    find_package(wxInspector REQUIRED)
+    # wxInspector 1.0.0 installs its headers but accidentally declares the
+    # INSTALL_INTERFACE include directory PRIVATE, so its imported target does
+    # not expose them to consumers. Restore the package prefix include path until
+    # the upstream export is fixed.
+    get_filename_component(WXINSPECTOR_PREFIX "${wxInspector_DIR}/../../.." ABSOLUTE)
+    target_include_directories(wxInspector::wxInspector INTERFACE "${WXINSPECTOR_PREFIX}/include")

    # wxInspector's exported interface names the release wxWidgets import
    # libraries, which a Debug build cannot link. wx is linked above instead.
@@ -186,7 +192,7 @@ endif ()
 # Add the Slic3r GUI library, libcurl, OpenGL and GLU libraries.
 if (SLIC3R_GUI)
 #    target_link_libraries(OrcaSlicer ws2_32 uxtheme setupapi libslic3r_gui ${wxWidgets_LIBRARIES})
-target_link_libraries(OrcaSlicer libslic3r_gui)
+target_link_libraries(OrcaSlicer libslic3r_gui wxInspector::wxInspector)
    if (MSVC)
        # Generate debug symbols even in release mode.
        target_link_options(OrcaSlicer PUBLIC "$<$<CONFIG:RELEASE>:/DEBUG>")
@@ -3434,9 +3434,14 @@ int CLI::run(int argc, char **argv)
                max_self_index = std::max(max_self_index, v);
                min_self_index = std::min(min_self_index, v);
            }
-            if (max_self_index > filament_count || min_self_index < 1) {
-                BOOST_LOG_TRIVIAL(warning) << boost::format("filament_self_index range [%1%, %2%] is invalid for filament_count %3%, regenerating")
-                        % min_self_index % max_self_index % filament_count;
+            // And a project saved with FEWER filaments than are now loaded (a
+            // one-filament project sliced with two --load-filaments) leaves the tables half filled:
+            // the variant matching below then reads past filament_extruder_variant and
+            // set_with_restore_2 throws an uncaught size error. Regenerate in that case too.
+            if (max_self_index > filament_count || min_self_index < 1 || max_self_index < filament_count
+                || (int) filament_self_index_opt->values.size() < filament_count) {
+                BOOST_LOG_TRIVIAL(warning) << boost::format("filament_self_index range [%1%, %2%] (size %4%) is invalid for filament_count %3%, regenerating")
+                        % min_self_index % max_self_index % filament_count % filament_self_index_opt->values.size();
                need_regenerate_self_index = true;
            }
        }
@@ -3527,6 +3532,10 @@ int CLI::run(int argc, char **argv)
                std::vector<string>& filament_variants = curr_variant_opt->values;
                filament_variants.resize(filament_count, get_extruder_variant_string(etDirectDrive, nvtStandard));
            }
+            // See the filament_self_index note above: one variant per filament for
+            // the filaments the project did not know about.
+            if ((int) curr_variant_opt->values.size() < filament_count)
+                curr_variant_opt->values.resize(filament_count, get_extruder_variant_string(etDirectDrive, nvtStandard));
            const ConfigOptionStrings *new_variant_opt = dynamic_cast<const ConfigOptionStrings*>(config.option("filament_extruder_variant", true));

            std::vector<int> new_variant_indice;
@@ -3535,7 +3544,7 @@ int CLI::run(int argc, char **argv)

            for (int i = 0; i < new_variant_count; i++)
            {
-                for (int j = old_start_indice[filament_index - 1]; j < old_start_indice[filament_index - 1] + old_variant_count; j++)
+                for (int j = old_start_indice[filament_index - 1]; j < old_start_indice[filament_index - 1] + old_variant_count && j < (int) curr_variant_opt->values.size(); j++)
                {
                    if (curr_variant_opt->values[j] == new_variant_opt->values[i]) {
                        new_variant_indice[i] = j;
@@ -3587,7 +3596,18 @@ int CLI::run(int argc, char **argv)
                                ConfigOptionVectorBase* opt_vec_dst = static_cast<ConfigOptionVectorBase*>(opt);
                                const ConfigOptionVectorBase* opt_vec_src = static_cast<const ConfigOptionVectorBase*>(source_opt);
                                //set with index
-                                opt_vec_dst->set_with_restore_2(opt_vec_src, new_variant_indice, old_start_indice[filament_index - 1], old_variant_count);
+                                try {
+                                    // A project with fewer filaments than are loaded: grow the
+                                    // destination to the filament's slot first (set_with_restore_2 only restores).
+                                    if (opt_vec_src->size() > 0 && opt_vec_dst->size() < size_t(old_start_indice[filament_index - 1] + old_variant_count))
+                                        opt_vec_dst->resize(size_t(old_start_indice[filament_index - 1] + old_variant_count), opt_vec_src);
+                                    opt_vec_dst->set_with_restore_2(opt_vec_src, new_variant_indice, old_start_indice[filament_index - 1], old_variant_count);
+                                } catch (const std::exception &ex) {   // Was an uncaught abort
+                                    BOOST_LOG_TRIVIAL(error) << boost::format("filament %1%: option %2% could not be applied: %3%") % filament_index % opt_key % ex.what();
+                                    boost::nowide::cerr << "filament " << filament_index << ": option " << opt_key << " could not be applied: " << ex.what() << std::endl;
+                                    record_exit_reson(outfile_dir, CLI_CONFIG_FILE_ERROR, 0, cli_errors[CLI_CONFIG_FILE_ERROR], sliced_info);
+                                    flush_and_exit(CLI_CONFIG_FILE_ERROR);
+                                }
                            }

                            continue;
@@ -3633,7 +3653,16 @@ int CLI::run(int argc, char **argv)
                    if (filament_options_with_variant.find(opt_key) != filament_options_with_variant.end()) {
                        std::vector<int> temp_variant_indice;
                        temp_variant_indice.resize(new_variant_count, -1);
-                        opt_vec_dst->set_with_restore_2(opt_vec_src, temp_variant_indice, old_start_indice[filament_index - 1], old_variant_count, true);
+                        try {
+                            if (opt_vec_src->size() > 0 && opt_vec_dst->size() < size_t(old_start_indice[filament_index - 1] + old_variant_count))   // See above
+                                opt_vec_dst->resize(size_t(old_start_indice[filament_index - 1] + old_variant_count), opt_vec_src);
+                            opt_vec_dst->set_with_restore_2(opt_vec_src, temp_variant_indice, old_start_indice[filament_index - 1], old_variant_count, true);
+                        } catch (const std::exception &ex) {   // Was an uncaught abort
+                            BOOST_LOG_TRIVIAL(error) << boost::format("filament %1%: option %2% could not be applied: %3%") % filament_index % opt_key % ex.what();
+                            boost::nowide::cerr << "filament " << filament_index << ": option " << opt_key << " could not be applied: " << ex.what() << std::endl;
+                            record_exit_reson(outfile_dir, CLI_CONFIG_FILE_ERROR, 0, cli_errors[CLI_CONFIG_FILE_ERROR], sliced_info);
+                            flush_and_exit(CLI_CONFIG_FILE_ERROR);
+                        }

                        if (opt_key == "filament_extruder_variant")
                            new_variant_counts[filament_index - 1] = opt_vec_src->size();
@@ -4139,6 +4168,10 @@ int CLI::run(int argc, char **argv)
        BOOST_LOG_TRIVIAL(info) << boost::format("%1%, set disable_wipe_tower_after_mapping back to false due to wrapping detect")%__LINE__;
    }

+    // Belt printers never get the classic wipe tower (see Print::has_wipe_tower()), so reserve no space for it.
+    const ConfigOptionBool* belt_printer_opt = m_print_config.option<ConfigOptionBool>("belt_printer");
+    const bool is_belt_printer = belt_printer_opt && belt_printer_opt->value;
+
    auto timelapse_type_opt = m_print_config.option("timelapse_type");
    bool is_smooth_timelapse = false;
    if (enable_timelapse && timelapse_type_opt && (timelapse_type_opt->getInt() == TimelapseType::tlSmooth))
@@ -4376,11 +4409,11 @@ int CLI::run(int argc, char **argv)
        }
    };

-    auto check_plate_wipe_tower = [get_print_sequence, is_smooth_timelapse](Slic3r::GUI::PartPlate* plate, int plate_index, DynamicPrintConfig& print_config, plate_obj_size_info_t &plate_obj_size_info) {
+    auto check_plate_wipe_tower = [get_print_sequence, is_smooth_timelapse, is_belt_printer](Slic3r::GUI::PartPlate* plate, int plate_index, DynamicPrintConfig& print_config, plate_obj_size_info_t &plate_obj_size_info) {
        plate_obj_size_info.obj_bbox= plate->get_objects_bounding_box();
        BOOST_LOG_TRIVIAL(info) << boost::format("plate %1%, object bbox: min {%2%, %3%, %4%} - max {%5%, %6%, %7%}")
                    %(plate_index+1) %plate_obj_size_info.obj_bbox.min.x() % plate_obj_size_info.obj_bbox.min.y() % plate_obj_size_info.obj_bbox.min.z() %plate_obj_size_info.obj_bbox.max.x() % plate_obj_size_info.obj_bbox.max.y() % plate_obj_size_info.obj_bbox.max.z();
-        if (!print_config.has("wipe_tower_x")) {
+        if (is_belt_printer || !print_config.has("wipe_tower_x")) {
            plate_obj_size_info.has_wipe_tower = false;
            BOOST_LOG_TRIVIAL(info) << boost::format("can not found wipe_tower_x in config, set to no wipe tower");
            return;
@@ -5250,7 +5283,7 @@ int CLI::run(int argc, char **argv)
                    }
                }

-                if ((!arrange_cfg.is_seq_print && (assemble_plate.filaments_count > 1))||(enable_wrapping_detect && !current_wrapping_exclude_area.empty()))
+                if (!is_belt_printer && ((!arrange_cfg.is_seq_print && (assemble_plate.filaments_count > 1)) || (enable_wrapping_detect && !current_wrapping_exclude_area.empty())))
                {
                    //prepare the wipe tower
                    int plate_count = partplate_list.get_plate_count();
@@ -5402,7 +5435,7 @@ int CLI::run(int argc, char **argv)
                bool is_seq_print = false;
                get_print_sequence(cur_plate, m_print_config, is_seq_print);

-                if (!is_seq_print && (assemble_plate.filaments_count > 1) && !has_wipe_tower_position)
+                if (!is_belt_printer && !is_seq_print && (assemble_plate.filaments_count > 1) && !has_wipe_tower_position)
                {
                    //prepare the wipe tower
                    auto printer_structure_opt = m_print_config.option<ConfigOptionEnum<PrinterStructure>>("printer_structure");
@@ -5570,7 +5603,7 @@ int CLI::run(int argc, char **argv)
                    };
                    const int max_filament_count = plate_count > 0 ? *std::max_element(plate_filament_counts.begin(), plate_filament_counts.end()) : 0;

-                    if (plate_needs_wipe_tower(max_filament_count))
+                    if (!is_belt_printer && plate_needs_wipe_tower(max_filament_count))
                    {
                        //prepare the wipe tower
                        auto printer_structure_opt = m_print_config.option<ConfigOptionEnum<PrinterStructure>>("printer_structure");
@@ -5677,7 +5710,7 @@ int CLI::run(int argc, char **argv)
                        BOOST_LOG_TRIVIAL(info) << __FUNCTION__ << boost::format(": found single object mode");
                    }

-                    if (m_print_config.has("wipe_tower_x") && (is_smooth_timelapse || !arrange_cfg.is_seq_print || (selected.size() <= 1))) {
+                    if (!is_belt_printer && m_print_config.has("wipe_tower_x") && (is_smooth_timelapse || !arrange_cfg.is_seq_print || (selected.size() <= 1))) {
                        float x;
                        float y;
                        if (duplicate_count > 0) {
@@ -6302,7 +6335,7 @@ int CLI::run(int argc, char **argv)
                // The stored (or default) tower position may not fit the tower these plates
                // need, and no CLI placement site runs on a plain slice - mirror the GUI's
                // reload clamp and fit every plate's tower into the printable area first.
-                if (m_print_config.option<ConfigOptionBool>("enable_prime_tower", true)->value) {
+                if (!is_belt_printer && m_print_config.option<ConfigOptionBool>("enable_prime_tower", true)->value) {
                    for (int index = 0; index < partplate_list.get_plate_count(); index++) {
                        if ((plate_to_slice != 0) && (plate_to_slice != (index + 1)))
                            continue;
@@ -521,11 +521,16 @@ int slice_all_printers(const std::string &vendor, const std::string &outdir)
        const std::string filament_name = bundle.filaments.get_selected_preset_name();
        const std::string what          = "Printer \"" + printer + "\"";
        const std::string file_base     = sanitize_filename(vendor_name) + "__" + sanitize_filename(printer);
+        // A belt printer has no wipe tower (it purges into a prism object on the belt), so its
+        // filament change is the plain tool change set_extruder() emits rather than the tower's block.
+        const bool        belt   = bundle.printers.get_selected_preset().config.opt_bool("belt_printer");
+        const std::string marker = belt ? "\nT1\n" : "CP TOOLCHANGE START";
        if (const std::string out = slice_selection(bundle, what, false, outdir, file_base); out.empty())
            ++failures;
-        else if (out.find("CP TOOLCHANGE START") == std::string::npos) {
-            // The filament change never rode the tower, so change_filament_gcode was not exercised.
-            BOOST_LOG_TRIVIAL(error) << what << " sliced but the filament change never fired (no CP TOOLCHANGE START)";
+        else if (out.find(marker) == std::string::npos) {
+            // The filament change never fired, so change_filament_gcode was not exercised.
+            BOOST_LOG_TRIVIAL(error) << what << " sliced but the filament change never fired (no "
+                                     << (belt ? "T1" : "CP TOOLCHANGE START") << ")";
            ++failures;
        }
        cover(bundle.prints.get_selected_preset());
@@ -300,7 +300,15 @@ Points get_shrink_bedpts(const DynamicPrintConfig* print_cfg, const ArrangeParam
 template<class PConf>
 void fill_config(PConf& pcfg, const ArrangeParams &params) {

-        if (params.is_seq_print) {
+        if (params.is_belt) {
+            // Pack from the end of the belt that prints first, and keep the pile on the
+            // bed when it is larger than the room around that end.
+            pcfg.starting_point = !params.belt_reversed    ? PConf::Alignment::BOTTOM_LEFT :
+                                  params.belt_axis == 1    ? PConf::Alignment::TOP_LEFT :
+                                                             PConf::Alignment::BOTTOM_RIGHT;
+            pcfg.clamp_to_bin = true;
+        }
+        else if (params.is_seq_print) {
            // Start placing the items from the center of the print bed
            pcfg.starting_point = PConf::Alignment::BOTTOM_LEFT;
        }
@@ -445,6 +453,50 @@ protected:
        return bindist;
    }

+    // Belt printers pack from the end of the belt that prints first, and a corner
+    // packer's checks (pile inside the bin, pack origin) apply to them as well.
+    bool corner_packing() const { return params.is_belt || m_pconf.starting_point == PConfig::Alignment::BOTTOM_LEFT; }
+
+    static double at(const Box::PointType &pt, int i) { return double(i == 0 ? getX(pt) : getY(pt)); }
+
+    // Position along the belt in print order: increasing from the end that prints first.
+    double belt_pos(const Box::PointType &pt) const { return params.belt_reversed ? -at(pt, params.belt_axis) : at(pt, params.belt_axis); }
+    double belt_start(const Box &bb) const { return belt_pos(params.belt_reversed ? bb.maxCorner() : bb.minCorner()); }
+    double belt_end(const Box &bb) const { return belt_pos(params.belt_reversed ? bb.minCorner() : bb.maxCorner()); }
+
+    // The corner of the bin the belt pile grows from.
+    Box::PointType belt_origin() const
+    {
+        const Box bb = sl::boundingBox(m_bin);
+        auto o = bb.minCorner();
+        if (params.belt_reversed) {
+            if (params.belt_axis == 0) setX(o, getX(bb.maxCorner()));
+            else                       setY(o, getY(bb.maxCorner()));
+        }
+        return o;
+    }
+
+    // An item's far edge in print order is what it costs (so a row fills across the
+    // belt before the pile advances), with a slight pull toward the near lateral
+    // edge and the same penalty as the bottom-left heuristic for sitting outside
+    // the corner.
+    double dist_along_belt(const Box &ibb)
+    {
+        const Box    bin = sl::boundingBox(m_bin);
+        const int    l   = 1 - params.belt_axis;
+        const double lat = at(ibb.minCorner(), l) - at(bin.minCorner(), l);
+        double       d   = belt_end(ibb) - belt_start(bin);
+        d += lat < 0 ? 10 * -lat : 0.1 * lat;
+        if (double behind = belt_start(ibb) - belt_start(bin); behind < 0)
+            d += 10 * -behind;
+        return norm(d);
+    }
+
+    double corner_bindist(const Box &ibb, const Slic3r::Point &origin_pack)
+    {
+        return params.is_belt ? dist_along_belt(ibb) : dist_for_BOTTOM_LEFT(ibb, origin_pack);
+    }
+
    double dist_to_bin(const Box& ibb, const Slic3r::Point& origin_pack, typename Packer::PlacementConfig::Alignment starting_point_alignment)
    {
        double bindist = 0;
@@ -534,8 +586,8 @@ protected:

            // The smalles distance from the arranged pile center:
            double dist = norm(*(std::min_element(dists.begin(), dists.end())));
-            if (m_pconf.starting_point == PConfig::Alignment::BOTTOM_LEFT) {
-                double bindist = dist_for_BOTTOM_LEFT(ibb, origin_pack);
+            if (corner_packing()) {
+                double bindist = corner_bindist(ibb, origin_pack);
                score = 0.2 * dist + 0.8 * bindist;
            }
            else {
@@ -592,8 +644,8 @@ protected:
            break;
        }
        case LAST_BIG_ITEM: {
-            if (m_pconf.starting_point == PConfig::Alignment::BOTTOM_LEFT) {
-                score = dist_for_BOTTOM_LEFT(ibb, origin_pack);
+            if (corner_packing()) {
+                score = corner_bindist(ibb, origin_pack);
            }
            else {
                if (m_pilebb.defined)
@@ -608,8 +660,8 @@ protected:
            // already processed bigger items.
            // No need to play around with the anchor points, the center will be
            // just fine for small items
-            if (m_pconf.starting_point == PConfig::Alignment::BOTTOM_LEFT)
-                score = dist_for_BOTTOM_LEFT(ibb, origin_pack);
+            if (corner_packing())
+                score = corner_bindist(ibb, origin_pack);
            else {
                // Align mainly around existing items
                score = 0.8 * norm(pl::distance(ibb.center(), bigbb.center()))+ 0.2*norm(pl::distance(ibb.center(), origin_pack));
@@ -710,6 +762,28 @@ protected:
            score += 1 * (new_extruder_cnt-last_extruder_cnt);
        }

+        // On a belt the parts print in belt order, so every colour change between
+        // parts is a filament change. Items arrive sorted by extruder and the pile
+        // grows from the leading end; keep each colour's run contiguous by charging
+        // an item for every packed item of another colour it does not fully follow,
+        // counting the tilted layers that reach belt_tilt_slope * height past that
+        // item's far edge.
+        if (params.is_belt && !params.is_seq_print) {
+            const std::set<int> item_colours(item.extrude_ids.begin(), item.extrude_ids.end());
+            const double        item_start = belt_start(ibb);
+            for (Item &p : m_items) {
+                if (p.is_virt_object)
+                    continue;
+                const std::set<int> p_colours(p.extrude_ids.begin(), p.extrude_ids.end());
+                const bool same_colour = std::includes(item_colours.begin(), item_colours.end(), p_colours.begin(), p_colours.end())
+                                      || std::includes(p_colours.begin(), p_colours.end(), item_colours.begin(), item_colours.end());
+                if (same_colour)
+                    continue;
+                if (item_start < belt_end(p.boundingBox()) + scaled(p.height * params.belt_tilt_slope))
+                    score += 10.;
+            }
+        }
+
        return std::make_tuple(score, fullbb);
    }

@@ -786,7 +860,8 @@ public:

            auto binbb = sl::boundingBox(m_bin);

-            auto starting_point = cfg.starting_point == PConfig::Alignment::BOTTOM_LEFT ? binbb.minCorner() : binbb.center();
+            auto starting_point = this->params.is_belt ? belt_origin() :
+                cfg.starting_point == PConfig::Alignment::BOTTOM_LEFT ? binbb.minCorner() : binbb.center();
            // if we have wipe tower, items should be arranged around wipe tower
            for (Item itm : items) {
                if (itm.is_wipe_tower) {
@@ -937,7 +1012,7 @@ std::function<double(const Item &, const ItemGroup&)> AutoArranger<ExPolygon>::g
        auto mp = m_merged_pile;
        mp.emplace_back(itm.transformedShape());
        auto chull = sl::convexHull(mp);
-        if (m_pconf.starting_point == PConfig::Alignment::BOTTOM_LEFT)
+        if (corner_packing())
        {
            if (!sl::isInside(chull, m_bin))
                score += LARGE_COST_TO_REJECT;
@@ -146,6 +146,13 @@ struct ArrangeParams {
    float nozzle_height = 0;
    float printable_height = 256.0;
    Vec2d align_center{ 0.5,0.5 };
+    // Belt printer: items print in the order they lie along the belt axis, from
+    // its low end unless belt_reversed, and a part's top prints
+    // belt_tilt_slope * height further along it than its base.
+    bool  is_belt         = false;
+    int   belt_axis       = 1;   // 0 = X, 1 = Y
+    bool  belt_reversed   = false;
+    float belt_tilt_slope = 1.f; // cot(belt tilt angle), 0 when the belt is not tilted

    ArrangePolygons excluded_regions;   // regions cant't be used
    ArrangePolygons nonprefered_regions; // regions can be used but not prefered
@@ -0,0 +1,554 @@
+#include <limits>
+#include "BeltBrim.hpp"
+
+#include "ClipperUtils.hpp"
+#include "Flow.hpp"
+#include "Layer.hpp"
+#include "Polygon.hpp"
+#include "Print.hpp"
+#include "ShortestPath.hpp"
+#include "Support/BeltFloorContext.hpp"
+#include "BoundingBox.hpp"
+#include "ExPolygon.hpp"
+#include "ExtrusionEntity.hpp"
+#include "ExtrusionEntityCollection.hpp"
+#include "Point.hpp"
+#include "Polyline.hpp"
+#include "PrintConfig.hpp"
+#include "libslic3r.h"
+
+#include <algorithm>
+#include <cmath>
+#include <cstddef>
+#include <cstdint>
+#include <cstdlib>
+#include <utility>
+#include <vector>
+
+namespace Slic3r {
+
+// ---------------------------------------------------------------- scaling
+
+static inline Point scale_u_point(const Point &p, int from_axis, double factor)
+{
+    // llround, not a cast: casting truncates toward zero, so a round trip would
+    // walk every vertex toward the origin by up to one unit per pass.
+    return from_axis == 0 ?
+        Point(coord_t(std::llround(double(p.x()) * factor)), p.y()) :
+        Point(p.x(), coord_t(std::llround(double(p.y()) * factor)));
+}
+
+static inline void scale_u_polygon(Polygon &poly, int from_axis, double factor)
+{
+    for (Point &p : poly.points)
+        p = scale_u_point(p, from_axis, factor);
+}
+
+ExPolygons belt_scale_u(const ExPolygons &src, const BeltBrimFrame &frame, double factor)
+{
+    ExPolygons out = src;
+    for (ExPolygon &ex : out) {
+        scale_u_polygon(ex.contour, frame.from_axis, factor);
+        for (Polygon &hole : ex.holes)
+            scale_u_polygon(hole, frame.from_axis, factor);
+    }
+    return out;
+}
+
+Polylines belt_scale_u(const Polylines &src, const BeltBrimFrame &frame, double factor)
+{
+    Polylines out = src;
+    for (Polyline &pl : out)
+        for (Point &p : pl.points)
+            p = scale_u_point(p, frame.from_axis, factor);
+    return out;
+}
+
+// ---------------------------------------------------------------- sweep
+
+ExPolygons sweep_ex(const ExPolygons &src, const Point &t)
+{
+    if (src.empty())
+        return {};
+    if (t == Point(0, 0))
+        return src;
+
+    // One parallelogram per boundary edge.  Together with P and P + t these
+    // cover the Minkowski sum exactly: for any q = p + s*t with p in P and
+    // s in [0, 1], let s* be the smallest lambda >= 0 with q - lambda*t in P.
+    // Either s* == 0 (so q is in P) or q - s* * t lies on some boundary edge e,
+    // putting q in that edge's parallelogram.  Hole edges must be included, or
+    // holes narrower than t along t would wrongly survive the sweep.
+    Polygons quads;
+    for (const ExPolygon &ex : src)
+        for (size_t c = 0; c < ex.num_contours(); ++ c)
+            for (const Line &e : ex.contour_or_hole(c).lines()) {
+                if (e.a == e.b)
+                    continue;
+                Polygon q;
+                q.points = { e.a, e.b, e.b + t, e.a + t };
+                // The non-zero fill rule counts a clockwise ring as -1, which
+                // would punch a hole instead of adding material.  Edges parallel
+                // to t give a zero-area quad; Clipper discards those harmlessly.
+                if (q.is_clockwise())
+                    q.reverse();
+                quads.emplace_back(std::move(q));
+            }
+
+    ExPolygons shifted = src;
+    for (ExPolygon &ex : shifted)
+        ex.translate(t);
+
+    // union_ex(ExPolygons, Polygons) uses pftNonZero, which is the fill rule the
+    // argument above relies on.
+    return union_ex(union_ex(src, shifted), quads);
+}
+
+// ---------------------------------------------------------------- brim region
+
+ExPolygons belt_brim_region(const ExPolygons    &footprint_flat,
+                            bool                 has_outer,
+                            bool                 has_inner,
+                            coord_t              brim_width,
+                            coord_t              object_gap,
+                            coord_t              leading,
+                            coord_t              lateral,
+                            const BeltBrimFrame &frame)
+{
+    if (footprint_flat.empty() || (! has_outer && ! has_inner))
+        return {};
+
+    ExPolygons out;
+
+    if (has_outer) {
+        // Offset the outer ring from the contours only, so a hole cannot punch
+        // through it.  Same reasoning as the plate brim in Brim.cpp.
+        Polygons contours;
+        contours.reserve(footprint_flat.size());
+        for (const ExPolygon &ex : footprint_flat)
+            contours.emplace_back(ex.contour);
+
+        // Inner and outer boundary offset from the same polygon, to avoid
+        // round-off mismatch between them.
+        ExPolygons inner = offset_ex(contours, float(object_gap), jtRound, SCALED_RESOLUTION);
+
+        // Close the interior before offsetting outwards.  A belt contact patch is often a
+        // narrow, broken-up strip, and the offset rings of two islands less than
+        // 2 x brim_width apart merge and fill the space between them - space that lies
+        // UNDER the part, which is not what "outer brim" means.  Closing also swallows
+        // holes in the patch for the same reason.  Concavity-filling only, so an apron or
+        // any other outward protrusion is untouched.
+        ExPolygons envelope = brim_width > 0 ? closing_ex(inner, float(brim_width)) : inner;
+
+        ExPolygons base  = envelope;
+        if (leading > 0) {
+            // Sweep downhill from the gapped keep-out, so the apron is contiguous with
+            // the ring instead of starting inside the gap.
+            const Point t = frame.from_axis == 0 ?
+                Point(frame.downhill_sign() * leading, 0) :
+                Point(0, frame.downhill_sign() * leading);
+            base = union_ex(base, sweep_ex(envelope, t));
+        }
+        if (lateral > 0) {
+            // Across the belt, both ways.  Swept from `base` so the apron is widened
+            // too, and in the flattened frame the cross-belt axis is unscaled, so this
+            // distance is already a true on-belt distance.
+            const Point t = frame.from_axis == 0 ? Point(0, lateral) : Point(lateral, 0);
+            ExPolygons widened = union_ex(sweep_ex(base, t), sweep_ex(base, Point(-t.x(), -t.y())));
+            base = union_ex(base, to_polygons(widened));
+        }
+        ExPolygons outer = offset_ex(base, float(brim_width), jtRound, SCALED_RESOLUTION);
+        expolygons_append(out, diff_ex(outer, envelope));
+    }
+
+    if (has_inner) {
+        // Holes reversed so a negative offset grows inward, mirroring Brim.cpp.
+        // No apron here: an apron growing into a hole interior is never useful.
+        Polygons holes;
+        for (const ExPolygon &ex : footprint_flat)
+            polygons_append(holes, ex.holes);
+        polygons_reverse(holes);
+        if (! holes.empty()) {
+            ExPolygons hole_inner = offset_ex(holes, - float(brim_width + object_gap));
+            ExPolygons hole_outer = offset_ex(holes, - float(object_gap));
+            expolygons_append(out, intersection_ex(diff_ex(hole_outer, hole_inner), holes));
+        }
+    }
+
+    return union_ex(out);
+}
+
+// ---------------------------------------------------------------- line lattice
+
+std::vector<coord_t> belt_brim_line_positions(coord_t u_lo,
+                                              coord_t u_hi,
+                                              coord_t pitch_u,
+                                              coord_t u_anchor)
+{
+    std::vector<coord_t> out;
+    if (pitch_u <= 0 || u_hi <= u_lo)
+        return out;
+
+    // Walk the lattice from just below u_lo.  Integer arithmetic throughout, so
+    // the half-open interval needs no epsilon: a point landing exactly on u_hi
+    // belongs to the next band.
+    int64_t k = int64_t(std::floor(double(u_lo - u_anchor) / double(pitch_u))) - 1;
+    while (u_anchor + coord_t(k) * pitch_u < u_lo)
+        ++ k;
+    for (;; ++ k) {
+        const coord_t u = u_anchor + coord_t(k) * pitch_u;
+        if (u >= u_hi)
+            break;
+        out.emplace_back(u);
+    }
+    return out;
+}
+
+// ---------------------------------------------------------------- pipeline
+
+// A band of the belt surface as an explicit box, clamped to `bounds` along the
+// shear axis.  Deliberately not BeltFloorContext::surface_polygon(): those
+// half-planes span +-1000 mm, which is wasteful to clip against and dangerous to
+// feed through the flattening scale.
+static Polygon band_box(const BoundingBox &bounds, int from_axis, coordf_t u_lo, coordf_t u_hi)
+{
+    coord_t lo = scale_(u_lo);
+    coord_t hi = scale_(u_hi);
+    const coord_t bmin = from_axis == 0 ? bounds.min.x() : bounds.min.y();
+    const coord_t bmax = from_axis == 0 ? bounds.max.x() : bounds.max.y();
+    lo = std::max(lo, bmin);
+    hi = std::min(hi, bmax);
+    Polygon poly;
+    if (hi <= lo)
+        return poly;
+    if (from_axis == 0)
+        poly.points = { Point(lo, bounds.min.y()), Point(hi, bounds.min.y()),
+                        Point(hi, bounds.max.y()), Point(lo, bounds.max.y()) };
+    else
+        poly.points = { Point(bounds.min.x(), lo), Point(bounds.max.x(), lo),
+                        Point(bounds.max.x(), hi), Point(bounds.min.x(), hi) };
+    return poly;
+}
+
+ExPolygons belt_brim_clip_leading_edge(const ExPolygons &region, const BeltBrimFrame &frame, coordf_t u_cut)
+{
+    if (region.empty())
+        return region;
+    BoundingBox keep_bb = get_extents(region);
+    keep_bb.offset(scale_(1.));
+    const bool    low_side = frame.downhill_sign() < 0;   // downhill is -u
+    const Polygon keep = band_box(keep_bb, frame.from_axis,
+        low_side ? unscale<double>(frame.from_axis == 0 ? keep_bb.min.x() : keep_bb.min.y()) : u_cut,
+        low_side ? u_cut : unscale<double>(frame.from_axis == 0 ? keep_bb.max.x() : keep_bb.max.y()));
+    return keep.empty() ? ExPolygons{} : intersection_ex(region, Polygons{ keep });
+}
+
+// Everything the per-band line generator needs, gathered once per object.
+struct BeltBrimContext
+{
+    BeltFloorContext ctx;
+    BeltBrimFrame    frame;
+    ExPolygons       region;      // brim region, object-local slicing XY
+    BoundingBox      region_bbox;
+    Flow             brim_flow;
+    coord_t          pitch_u   = 0;
+    coord_t          u_anchor  = 0;
+    double           in_plane_pitch = 0.;   // mm
+};
+
+// Emit the cross-belt brim lines that belong to the band [print_z - height, print_z].
+static void belt_brim_band_paths(const BeltBrimContext      &bc,
+                                 coordf_t                    print_z,
+                                 coordf_t                    height,
+                                 const Polygons             &obstacles,
+                                 ExtrusionEntityCollection  &out,
+                                 ExPolygons                 &areas_out)
+{
+    coordf_t u_lo = bc.ctx.cutoff_u(print_z - height);
+    coordf_t u_hi = bc.ctx.cutoff_u(print_z);
+    if (u_lo > u_hi)
+        std::swap(u_lo, u_hi);
+
+    // How wide this band is measured ON the belt, versus one nominal bead.
+    const double band_in_plane = (u_hi - u_lo) * bc.frame.u_stretch();
+
+    // Fraction of the layer height at which a line sits above the belt.  Toward the
+    // downhill edge, so the sheet is reasonably thick while the nozzle stays clear of
+    // the belt itself.
+    static constexpr double BAND_CLEARANCE_FRACTION = 0.75;
+
+    std::vector<coord_t> us;
+    double uniform_clearance = 0.;   // 0 => derive per line from its own position
+    double line_pitch        = bc.in_plane_pitch;
+    // One line also serves a band up to half a bead wider than the nominal pitch (a 0.3 mm
+    // first layer at 45 degrees): its flow is matched to the band, so the bead is that much
+    // wider. Two lattice lines in such a band would land almost on top of each other.
+    if (band_in_plane <= 1.5 * bc.in_plane_pitch + EPSILON) {
+        // Steep belt, which is the normal case: the band is narrower than one bead, so
+        // exactly one line fits.  Place it at a FIXED fraction of the band rather than
+        // on a nominal-spacing lattice.  On a lattice each line lands at an arbitrary
+        // point in its band, the clearance sweeps [0, height] from band to band, and the
+        // bead width therefore varies by 2x - visible as ragged, uneven brim lines.
+        // Anchoring to the band makes the clearance identical everywhere, so every bead
+        // is the same width.
+        //
+        // The spacing is then whatever the bands give (height / sin(tilt) on the belt)
+        // rather than the nominal bead spacing, so the flow below is matched to THAT
+        // pitch.  Matched flow at the real pitch is what keeps the sheet uniform and
+        // gap-free; using nominal flow at band spacing would over-feed it.
+        us.push_back(scale_(bc.ctx.cutoff_u(print_z - BAND_CLEARANCE_FRACTION * height)));
+        uniform_clearance = BAND_CLEARANCE_FRACTION * height;
+        line_pitch        = band_in_plane;
+    } else {
+        // Shallow belt: the band is wider than a bead, so it takes several lines and they
+        // have to sit on the nominal lattice.  Their clearances then differ, and so do
+        // their widths - unavoidable here, but shallow belts are the rare case.
+        us = belt_brim_line_positions(scale_(u_lo), scale_(u_hi), bc.pitch_u, bc.u_anchor);
+    }
+    if (us.empty())
+        return;
+
+    const Polygons region_polys = to_polygons(bc.region);
+
+    // One lattice line at a time: the clearance - and therefore the extrusion
+    // volume - is a property of the line's u, so the pieces of different lines
+    // must not be pooled before the flow is resolved.
+    // Overshoot the region so the clip, not the line's ends, decides the extent.
+    const coord_t margin = coord_t(SCALED_EPSILON) + 1;
+    coord_t       u_prev = std::numeric_limits<coord_t>::min();
+    for (coord_t u : us) {
+        // Nozzle-to-belt clearance for this line.  Constant along the line, because the
+        // belt height depends only on the shear-axis coordinate.  Band-anchored lines
+        // share one clearance by construction; lattice lines (shallow belts, or a first
+        // layer thick enough that the band is wider than a bead) each get their own.
+        //
+        // A lattice line can fall where the belt is only a hair below the band's print_z.
+        // The bead there would be laid scraping the belt while its flow is sized for a
+        // taller cell, so it is moved uphill to the same fraction of the band the
+        // single-line case uses.  (The clearance is along slice Z; the real gap under the
+        // nozzle is clearance x cos(tilt), 0.53 h at 45 degrees for the 0.75 fraction.)
+        double clearance = uniform_clearance;
+        if (clearance <= 0.) {
+            const Point probe = bc.frame.from_axis == 0 ? Point(u, 0) : Point(0, u);
+            clearance = print_z - bc.ctx.floor_print_z(probe);
+            if (clearance < BAND_CLEARANCE_FRACTION * height) {
+                clearance = BAND_CLEARANCE_FRACTION * height;
+                u         = scale_(bc.ctx.cutoff_u(print_z - clearance));
+            }
+            clearance = std::min(clearance, height);
+        }
+        // A line moved uphill can land on, or almost on, its neighbour; two beads closer
+        // than half a pitch would be laid into the same cell.
+        if (u_prev != std::numeric_limits<coord_t>::min() && std::abs(u - u_prev) < bc.pitch_u / 2)
+            continue;
+        u_prev = u;
+
+        Polyline line;
+        if (bc.frame.from_axis == 0)
+            line.points = { Point(u, coord_t(bc.region_bbox.min.y() - margin)),
+                            Point(u, coord_t(bc.region_bbox.max.y() + margin)) };
+        else
+            line.points = { Point(coord_t(bc.region_bbox.min.x() - margin), u),
+                            Point(coord_t(bc.region_bbox.max.x() + margin), u) };
+
+        Polylines pieces = intersection_pl(Polylines{ line }, region_polys);
+        if (! obstacles.empty())
+            pieces = diff_pl(pieces, obstacles);
+        if (pieces.empty())
+            continue;
+
+        // with_cross_section, not with_height: it reaches the prescribed volume while
+        // KEEPING the extrusion spacing, so the bead is sized to fill exactly one
+        // pitch x clearance cell of the sheet.
+        const Flow f = bc.brim_flow.with_cross_section(float(line_pitch * clearance));
+
+        // Footprint of these beads, for the first-layer convex hull and bbox.
+        for (const Polygon &p : offset(pieces, 0.5f * float(f.scaled_width())))
+            areas_out.emplace_back(ExPolygon(p));
+
+        extrusion_entities_append_paths(out.entities, chain_polylines(std::move(pieces)),
+                                        erBrim, f.mm3_per_mm(), f.width(), float(clearance));
+    }
+}
+
+// Union of everything extruded at `print_z` that the brim must keep clear of, expressed
+// in `self`'s local slicing frame.  Includes `self` itself: its slice at this Z can
+// overhang outside the belt footprint and land in the brim ring, which the flattened
+// brim_object_gap - a belt-plane separation - does not cover.
+//
+// THREADING: this runs inside posSupportMaterial, which Print::process() executes for all
+// objects in a tbb::parallel_for (Print.cpp).  Object slices are finished by then and safe
+// to read across objects, but SUPPORT layers are not: another object's thread may be
+// inside clear_support_layers() - which deletes the SupportLayer pointers - right now, so
+// touching a foreign object's support_layers() here is a use-after-free.  Only this
+// object's own supports are consulted; they are complete, because make_belt_brim() runs at
+// the tail of this object's own generate_support_material().  The cost is that the brim
+// does not dodge a *different* object's support at the same Z, which needs the objects to
+// overlap in the belt direction in the first place.
+// `region_bbox` bounds the brim; anything outside it cannot clip a brim line, so whole
+// objects are skipped without materialising their polygons.  On a typical plate the
+// objects do not overlap and every foreign object drops out here, which matters because
+// this runs once per band - hundreds of times per object.
+static Polygons belt_brim_obstacles(const Print &print, const PrintObject &self,
+                                    const BoundingBox &region_bbox, coordf_t print_z, coordf_t tol)
+{
+    const Point shift_self = self.instances().empty() ? Point(0, 0)
+                                                      : self.instances().front().shift_without_plate_offset();
+    Polygons out;
+    for (const PrintObject *o : print.objects()) {
+        const bool is_self = (o == &self);
+        for (const PrintInstance &inst : o->instances()) {
+            const Point delta = inst.shift_without_plate_offset() - shift_self;
+            if (const Layer *l = o->get_layer_at_printz(print_z, tol)) {
+                BoundingBox lb = get_extents(l->lslices);
+                lb.translate(delta.x(), delta.y());
+                if (lb.overlap(region_bbox)) {
+                    Polygons ps = to_polygons(l->lslices);
+                    for (Polygon &p : ps)
+                        p.translate(delta);
+                    polygons_append(out, std::move(ps));
+                }
+            }
+            if (! is_self)
+                continue;
+            if (const SupportLayer *sl = o->get_support_layer_at_printz(print_z, tol)) {
+                Polygons ps = sl->support_fills.polygons_covered_by_spacing();
+                for (Polygon &p : ps)
+                    p.translate(delta);
+                polygons_append(out, std::move(ps));
+            }
+        }
+    }
+    if (out.size() < 2)
+        return out;   // union_() of 0 or 1 polygons is pure overhead
+    return union_(out);
+}
+
+void make_belt_brim(PrintObject &object)
+{
+    object.clear_belt_brim();
+    if (! object.has_belt_brim())
+        return;
+
+    const Print &print = *object.print();
+    BeltBrimContext bc;
+    if (! bc.ctx.init(object.slicing_parameters(), print.config()))
+        return;
+    bc.frame = BeltBrimFrame{ bc.ctx.shear_factor(), bc.ctx.from_axis() };
+
+    const size_t nlayers = object.layers().size();
+    if (nlayers == 0)
+        return;
+
+    // 1. Belt footprint: the union of each layer's slice clipped to that layer's
+    //    own contact band.  This is the object's bottom face, which on a belt is
+    //    spread over every layer instead of sitting in layer 0.
+    ExPolygons footprint_acc;
+    for (size_t i = 0; i < nlayers; ++ i) {
+        const Layer &layer = *object.layers()[i];
+        if (layer.lslices.empty())
+            continue;
+        // print_z - height, not the previous layer's print_z: variable layer
+        // heights make the latter wrong.
+        coordf_t u_lo = bc.ctx.cutoff_u(layer.print_z - layer.height);
+        coordf_t u_hi = bc.ctx.cutoff_u(layer.print_z);
+        if (u_lo > u_hi)
+            std::swap(u_lo, u_hi);
+        BoundingBox bb = get_extents(layer.lslices);
+        bb.offset(scale_(1.));
+        const Polygon band = band_box(bb, bc.frame.from_axis, u_lo, u_hi);
+        if (band.empty())
+            continue;
+        expolygons_append(footprint_acc, intersection_ex(layer.lslices, Polygons{ band }));
+    }
+    const ExPolygons footprint = union_ex(footprint_acc);
+    if (footprint.empty())
+        return;
+
+    // 2. Brim region, offset in the flattened (true on-belt) metric.
+    const PrintObjectConfig &cfg = object.config();
+    bc.brim_flow = print.brim_flow();
+    const double  flow_w = bc.brim_flow.scaled_spacing() * SCALING_FACTOR;
+    // Quantize to an even number of lines, as the plate brim does.
+    const coord_t width   = scale_(std::floor(cfg.brim_width.value / flow_w / 2) * flow_w * 2);
+    const coord_t leading = scale_(cfg.leading_brim_length.value);
+    const coord_t lateral = scale_(cfg.extra_brim_width.value);
+    const coord_t gap     = scale_(cfg.brim_object_gap.value);
+
+    // Belt printers collapse Auto / Mouse ear / Painted to outer-only: the auto width
+    // heuristic and flat ear discs have no meaning on a tilted plane.  Leading-edge-only
+    // is an outer brim too; it is narrowed down to the first contact below.
+    const BrimType bt = cfg.brim_type.value;
+    const bool has_outer = bt == btOuterOnly || bt == btOuterAndInner
+                        || bt == btAutoBrim  || bt == btEar || bt == btPainted
+                        || bt == btLeadingEdgeOnly;
+    const bool has_inner = bt == btInnerOnly || bt == btOuterAndInner;
+
+    bc.region = belt_unflatten(
+        belt_brim_region(belt_flatten(footprint, bc.frame), has_outer, has_inner,
+                         width, gap, leading, lateral, bc.frame),
+        bc.frame);
+
+    if (bt == btLeadingEdgeOnly && ! bc.region.empty())
+        // The cut is the uphill edge of the first layer's contact band: everything
+        // past it belongs to later contacts.
+        bc.region = belt_brim_clip_leading_edge(bc.region, bc.frame,
+                                                bc.ctx.cutoff_u(object.layers().front()->print_z));
+
+    if (bc.region.empty())
+        return;
+    bc.region_bbox = get_extents(bc.region);
+
+    // 3. Line lattice.  Fixed pitch in the flattened metric, anchored at the
+    //    footprint's leading-most edge so lines stay collinear across
+    //    disconnected islands and across the apron prologue.
+    bc.pitch_u = std::max<coord_t>(1, coord_t(bc.brim_flow.scaled_spacing() * bc.frame.cos_tilt()));
+    bc.in_plane_pitch = unscale<double>(bc.pitch_u) * bc.frame.u_stretch();
+    {
+        const BoundingBox fbb = get_extents(footprint);
+        const bool low_side = bc.frame.shear > 0.;
+        bc.u_anchor = bc.frame.from_axis == 0 ? (low_side ? fbb.min.x() : fbb.max.x())
+                                              : (low_side ? fbb.min.y() : fbb.max.y());
+    }
+
+    // 4. Bands coincident with an object layer.
+    std::vector<ExtrusionEntityCollection> by_layer(nlayers);
+    std::vector<ExPolygons>                areas_by_layer(nlayers);
+    for (size_t i = 0; i < nlayers; ++ i) {
+        const Layer &layer = *object.layers()[i];
+        const Polygons obstacles = belt_brim_obstacles(print, object, bc.region_bbox, layer.print_z, 0.5 * layer.height);
+        belt_brim_band_paths(bc, layer.print_z, layer.height, obstacles, by_layer[i], areas_by_layer[i]);
+    }
+
+    // 5. Apron prologue: the part of the region downhill of the object's first
+    //    layer, which has no object layer to ride on.
+    std::vector<BeltBrimBand> prologue;
+    {
+        const Layer   &first  = *object.layers().front();
+        const coordf_t h      = first.height;
+        const bool     low_side = bc.frame.shear > 0.;
+        const coord_t  u_lead_s = bc.frame.from_axis == 0
+            ? (low_side ? bc.region_bbox.min.x() : bc.region_bbox.max.x())
+            : (low_side ? bc.region_bbox.min.y() : bc.region_bbox.max.y());
+        const coordf_t u_lead  = unscale<double>(u_lead_s);
+        // print_z at which the belt surface crosses the region's leading edge.
+        const coordf_t z_lead  = bc.ctx.shear_factor() * u_lead
+                               + bc.ctx.floor_offset() + bc.ctx.z_shift();
+        if (h > EPSILON)
+            for (coordf_t z = first.print_z - h; z > z_lead - h; z -= h) {
+                const Polygons obstacles = belt_brim_obstacles(print, object, bc.region_bbox, z, 0.5 * h);
+                BeltBrimBand band;
+                band.print_z = z;
+                band.height  = h;
+                belt_brim_band_paths(bc, z, h, obstacles, band.fills, band.areas);
+                if (! band.fills.empty())
+                    prologue.emplace_back(std::move(band));
+            }
+        // Lowest Z first, so collect_layers_to_print sees them in print order.
+        std::reverse(prologue.begin(), prologue.end());
+    }
+
+    object.set_belt_brim(std::move(by_layer), std::move(areas_by_layer), std::move(prologue));
+}
+
+} // namespace Slic3r
@@ -0,0 +1,178 @@
+#ifndef slic3r_BeltBrim_hpp_
+#define slic3r_BeltBrim_hpp_
+
+#include "ExPolygon.hpp"
+#include "ExtrusionEntityCollection.hpp"
+#include "Point.hpp"
+#include "Polyline.hpp"
+#include "libslic3r.h"
+
+#include <cmath>
+#include <vector>
+
+// Belt-printer brim geometry.
+//
+// A belt printer slices in a ROTATED frame, so the belt surface is not the
+// Z=0 bed plane but a tilted plane in slicing space:
+//
+//     z_slicing(u) = shear * u + floor_offset + z_shift,   u = X or Y
+//
+// where `shear == tan(tilt)` (SlicingParameters::belt_floor_shear_factor) and
+// the axis is selected by SlicingParameters::belt_floor_from_axis.  See
+// Support/BeltFloorContext.hpp for the canonical accessors.
+//
+// Consequences that drive everything in this file:
+//
+//   * A horizontal slicing layer touches the belt only along a narrow strip at
+//     its leading edge, `layer_height / shear` wide (~0.2 mm at 45 degrees).
+//     The object's belt footprint - its bottom face - is therefore spread over
+//     every layer, not contained in layer 0.
+//   * Distances measured in slicing XY are NOT on-belt distances: moving `du`
+//     along the shear axis travels `du / cos(tilt)` across the belt.  So brim
+//     offsets have to be taken in a "flattened" space where the shear axis is
+//     stretched by `1 / cos(tilt)`, then mapped back.
+//   * Brim ahead of the part (downhill) lies at slicing Z BELOW the object's
+//     first layer, because the object's layer 0 is precisely its leading
+//     contact with the belt.
+//
+// Everything here is pure geometry on ExPolygons/Polylines so it can be unit
+// tested without a Print.  Keep user-visible strings out of this file: it is
+// not listed in localization/i18n/list.txt.
+
+namespace Slic3r {
+
+// Tilt window within which the BELT plane, not the bed plane, is the adhesion
+// surface.  Below ~1 degree a belt is a flat bed as far as adhesion goes, and the
+// contact band would be layer_height/sin(tilt) - tens of millimetres - so the
+// ordinary plate brim is both correct and cheaper.  Above ~85 degrees the whole
+// brim compresses into a sliver and is not worth generating.
+inline constexpr double BELT_BRIM_MIN_TILT_DEG = 1.;
+inline constexpr double BELT_BRIM_MAX_TILT_DEG = 85.;
+
+// Description of the tilted belt plane, reduced to what the brim geometry needs.
+struct BeltBrimFrame
+{
+    // tan(tilt).  Sign selects which way is downhill.
+    double shear     = 0.;
+    // 0 = X, 1 = Y.  Matches BeltFloorContext::from_axis().
+    int    from_axis = 1;
+
+    // 1 / cos(tilt).  Stretch factor that turns a projected distance along
+    // `from_axis` into the true distance travelled across the belt.
+    double u_stretch() const { return std::sqrt(1. + shear * shear); }
+    // cos(tilt).  The inverse mapping.
+    double cos_tilt()  const { return 1. / this->u_stretch(); }
+    // Downhill is where the belt surface is lower, i.e. printed earlier, i.e.
+    // the leading edge of the part.  For shear > 0 that is -u.
+    int    downhill_sign() const { return shear > 0. ? -1 : +1; }
+};
+
+// Scale only the `from_axis` component by `factor`, rounding to nearest.
+//
+// Deliberately not MultiPoint::scale(fx, fy) / ExPolygon::scale(fx, fy): those
+// truncate toward zero, which is asymmetric about the origin and loses up to a
+// full coordinate unit per vertex on every round trip.
+ExPolygons belt_scale_u(const ExPolygons &src, const BeltBrimFrame &frame, double factor);
+Polylines  belt_scale_u(const Polylines  &src, const BeltBrimFrame &frame, double factor);
+
+// Into / out of the space where Euclidean offsets equal true on-belt distances.
+inline ExPolygons belt_flatten(const ExPolygons &src, const BeltBrimFrame &frame)
+    { return belt_scale_u(src, frame, frame.u_stretch()); }
+inline ExPolygons belt_unflatten(const ExPolygons &src, const BeltBrimFrame &frame)
+    { return belt_scale_u(src, frame, frame.cos_tilt()); }
+
+// Minkowski sum of `src` with the segment [0, t]: the region swept by sliding
+// `src` along t.  Used to grow the brim downhill for "extra brim width".
+//
+// Implemented as union_(P, P + t, {parallelogram per boundary edge}) over ALL
+// contours including holes, with every parallelogram forced counter-clockwise
+// so the non-zero fill rule closes holes narrower than t along the sweep
+// direction.  A hole survives exactly when it is wider than |t| measured along
+// t - not when it is wider in its narrowest Euclidean direction.
+ExPolygons sweep_ex(const ExPolygons &src, const Point &t);
+
+// "Leading edge only": keep the part of a brim region (unflattened, slicing XY)
+// at or downhill of the object's first contact with the belt, so the part is
+// supported as it lands and nothing is printed alongside it afterwards.  `u_cut`
+// is the uphill edge of the first layer's contact band along `frame.from_axis`,
+// in mm (BeltFloorContext::cutoff_u of the first layer); downhill is the side
+// `frame.downhill_sign()` points to.
+ExPolygons belt_brim_clip_leading_edge(const ExPolygons &region, const BeltBrimFrame &frame, coordf_t u_cut);
+
+// Brim region for one already-flattened belt footprint.  All lengths are scaled
+// and measured in the flattened (true on-belt) metric.
+//
+// `has_outer` / `has_inner` are the resolved BrimType: belt printers collapse
+// Auto / Mouse ear / Painted to outer-only, so the caller does that mapping and
+// this function never needs PrintConfig.
+//
+// Two directional extras are applied to the footprint before the outer offset, so
+// each one buys reach in one direction only:
+//
+//   `leading` (leading_brim_length) sweeps the footprint DOWNHILL along the belt,
+//   so every leading-facing edge gains an apron ahead of it.
+//   `lateral`  (extra_brim_width)   sweeps it BOTH WAYS across the belt, widening
+//   the brim sideways without pushing it further ahead or behind.
+//
+// Neither is applied to the inner (hole) ring.
+ExPolygons belt_brim_region(const ExPolygons   &footprint_flat,
+                            bool                has_outer,
+                            bool                has_inner,
+                            coord_t             brim_width,
+                            coord_t             object_gap,
+                            coord_t             leading,
+                            coord_t             lateral,
+                            const BeltBrimFrame &frame);
+
+// Brim line positions for one layer band.
+//
+// Lines sit on a fixed lattice `u_anchor + k * pitch_u` so the on-belt spacing
+// between neighbouring brim lines is constant regardless of how the lattice
+// falls across layer bands.  Snapping to band centres instead would quantise
+// the spacing to whole bands and under-deposit by ~35% at 45 degrees.
+//
+// The band is half-open, [u_lo, u_hi), so every lattice point belongs to
+// exactly one band: none duplicated at a boundary, none dropped.  A band
+// narrower than the pitch simply yields nothing; a band much wider (shallow
+// tilt) yields several lines.
+std::vector<coord_t> belt_brim_line_positions(coord_t u_lo,
+                                              coord_t u_hi,
+                                              coord_t pitch_u,
+                                              coord_t u_anchor);
+
+// ---------------------------------------------------------------- pipeline
+
+// One brim-only layer printed BEFORE the object's first layer, carrying the
+// apron that has to be stuck to the belt ahead of the part.
+//
+// Deliberately not a Layer subclass.  A synthetic Layer would inherit id()
+// semantics that leak into initial-layer temperature selection, the spiral vase
+// probe, gradual interpolation, avoid-crossing-perimeters and cooling, all of
+// which key off Layer::id() == 0 or off a layer's regions.  A plain record
+// carries only what the emitter needs.
+//
+// `height` is the LAYER height, used for the Z move and ordering metadata only.
+// Each extrusion path inside `fills` carries its own height, equal to that
+// line's nozzle-to-belt clearance, which varies across the band.
+struct BeltBrimBand
+{
+    coordf_t                  print_z = 0.;
+    coordf_t                  height  = 0.;
+    // erBrim paths in the object's local slicing frame, untranslated.
+    ExtrusionEntityCollection fills;
+    // Footprint of those paths, for the first-layer convex hull / bbox.
+    ExPolygons                areas;
+};
+
+class PrintObject;
+
+// Generate the belt brim for one object: fills its per-object-layer bands and
+// its apron prologue.  No-op unless PrintObject::has_belt_brim().
+//
+// Runs inside posSupportMaterial rather than the brim step, because the prologue
+// print_z values must exist before ToolOrdering is built at psWipeTower.
+void make_belt_brim(PrintObject &object);
+
+} // namespace Slic3r
+
+#endif // slic3r_BeltBrim_hpp_
@@ -0,0 +1,73 @@
+#include "BeltGCode.hpp"
+#include "GCodeWriter.hpp"
+#include "GCode/BeltKinematics.hpp"
+#include "BeltTransform.hpp"
+#include "Print.hpp"
+#include "Point.hpp"
+#include "PrintConfig.hpp"
+#include "libslic3r.h"
+#include <cstdlib>
+
+namespace Slic3r {
+
+void BeltGCode::init_belt_writer(Print &print)
+{
+    // Axis remap and build volume max are set by base GCode after init_belt_writer
+    // returns; set_kinematics() replays them, so install order does not matter.
+    install_belt_kinematics(m_writer, print.config());
+    m_writer.set_force_normal_lift(true);
+}
+
+void BeltGCode::write_belt_header(GCodeOutputStream &file, const Print &print)
+{
+    const auto &full_cfg = print.full_print_config();
+    // Slicing rotation: the belt tilt (axis + angle) and the single source of truth
+    // for the physical tilt the G-code viewer uses to enable belt view.
+    file.write_format("; belt_slice_rotation = %s\n", full_cfg.opt_serialize("belt_slice_rotation").c_str());
+    file.write_format("; belt_slice_rotation_angle = %.1f\n", print.config().belt_slice_rotation_angle.value);
+    file.write_format("; belt_slice_rotation_global = %d\n", print.config().belt_slice_rotation_global.value ? 1 : 0);
+    // Pre-slice remap configs
+    file.write_format("; preslice_remap_x = %s\n", full_cfg.opt_serialize("preslice_remap_x").c_str());
+    file.write_format("; preslice_remap_y = %s\n", full_cfg.opt_serialize("preslice_remap_y").c_str());
+    file.write_format("; preslice_remap_z = %s\n", full_cfg.opt_serialize("preslice_remap_z").c_str());
+    file.write_format("; preslice_remap_global = %d\n", print.config().preslice_remap_global.value ? 1 : 0);
+    file.write_format("; belt_preslice_global = %d\n", print.config().belt_preslice_global.value ? 1 : 0);
+    // Machine-frame transform: shear (tan) + scale (1/cos) derived from the belt
+    // tilt angle (or belt_frame_tilt_angle when decoupled).
+    file.write_format("; belt_frame_tilt_decouple = %d\n", print.config().belt_frame_tilt_decouple.value ? 1 : 0);
+    file.write_format("; belt_frame_tilt_angle = %.1f\n", print.config().belt_frame_tilt_angle.value);
+}
+
+void BeltGCode::on_set_origin(const PrintObject * /*obj*/, const Point & /*inst_shift*/)
+{
+    // Global pre-slice mode: adjust origin using computed correction.
+    // Transform the origin through the belt pipeline so that
+    // back_transform(T * origin) = origin (correct machine position).
+    //
+    // Flags that trigger this path:
+    //   belt_preslice_global         — full pipeline (rotation * remap) is global
+    //   preslice_remap_global        — only the pre-slice remap is global
+    //   belt_slice_rotation_global   — slicing rotation treated as global (matches
+    //                                  the per-instance Z-offset added in PrintObjectSlice.cpp)
+    // The XY origin adjustment uses the FULL forward transform, because the
+    // back_transform applied during G-code emission is always the inverse of
+    // the full pipeline.
+    bool use_global = m_config.belt_preslice_global.value
+        || (m_config.preslice_remap_global.value
+            && BeltTransformPipeline::has_preslice_remap(m_config))
+        || (m_config.belt_slice_rotation_global.value
+            && m_config.belt_slice_rotation.value != BeltRotationAxis::None
+            && std::abs(m_config.belt_slice_rotation_angle.value) > EPSILON);
+    if (!use_global)
+        return;
+
+    // Adjust origin: transform through belt forward pipeline so that
+    // the back-transform correctly recovers model-space positions.
+    Transform3d T = BeltTransformPipeline::build_forward_transform(m_config);
+    Vec2d cur_origin = this->origin();
+    Vec3d origin3d(cur_origin.x(), cur_origin.y(), 0.);
+    Vec3d adjusted = T.linear() * origin3d;
+    this->set_origin(Vec2d(adjusted.x(), adjusted.y()));
+}
+
+} // namespace Slic3r
@@ -0,0 +1,25 @@
+#pragma once
+
+#include "GCode.hpp"
+#include "Point.hpp"
+#include "Print.hpp"
+
+namespace Slic3r {
+
+// Belt-printer-specific GCode export.
+//
+// Inherits from GCode and overrides virtual hooks to:
+// - Install a BeltKinematics on the GCodeWriter
+// - Write belt configuration to the G-code header
+// - Adjust the origin for global pre-slice transforms when switching instances
+// (Arc fitting is disabled for belt printers by BeltKinematics::supports_arc_moves(),
+//  which the base GCode::should_disable_arc_fitting() consults -- no override needed.)
+class BeltGCode : public GCode
+{
+protected:
+    void init_belt_writer(Print &print) override;
+    void write_belt_header(GCodeOutputStream &file, const Print &print) override;
+    void on_set_origin(const PrintObject *obj, const Point &inst_shift) override;
+};
+
+} // namespace Slic3r
@@ -0,0 +1,433 @@
+// ORCA-Belt: backend of the belt purge tower (the belt replacement for the
+// classic wipe/prime tower).
+//
+// Kept in its own translation unit so the belt-purge logic stays out of the way
+// of unrelated upstream changes to Print.cpp / PrintObjectSlice.cpp and carries
+// no regression risk for normal printers: none of these methods do anything
+// unless the print is a belt printer with the belt purge tower enabled.
+//
+//   Print::has_belt_purge_tower()      - is the belt purge tower active?
+//   Print::_align_belt_purge_layers()  - snap the prism's layer grid onto the
+//                                        printed objects' grid
+//   Print::_plan_belt_purge()          - route filament-change purging into the
+//                                        prism (flush-into-objects), no wipe tower
+//   PrintObject::belt_shift_layer_grid()      - shift a sliced layer grid
+//   PrintObject::belt_truncate_layers_above() - cancel the prism past the last swap
+//
+// (Declarations live in Print.hpp alongside the rest of the Print interface.)
+
+#include "Print.hpp"
+#include "PrintConfig.hpp"
+#include "Exception.hpp"
+#include "GCode/ToolOrdering.hpp"
+#include "Layer.hpp"
+#include "ExtrusionEntity.hpp"
+#include "ExtrusionEntityCollection.hpp"
+#include "I18N.hpp"
+#include "format.hpp"
+#include "LocalesUtils.hpp"
+#include "libslic3r.h"
+#include "BeltBrim.hpp"
+#include "PrintBase.hpp"
+
+#include <algorithm>
+#include <cmath>
+#include <limits>
+
+#include <boost/log/trivial.hpp>
+#include <cassert>
+#include <cstddef>
+#include <functional>
+#include <utility>
+#include <vector>
+
+namespace Slic3r {
+
+// Belt purge prism: purging after filament changes is routed into a sliced
+// prism object via the flush-into-objects machinery instead of a wipe tower.
+bool Print::has_belt_purge_tower() const
+{
+    // Its own purge-tower "type", gated by the belt-only enable_belt_purge_tower
+    // option (not the classic enable_prime_tower).
+    if (!(m_config.belt_printer.value
+          && m_config.enable_belt_purge_tower.value
+          && !m_config.spiral_mode.value
+          && m_config.filament_diameter.values.size() > 1))
+        return false;
+
+    return std::any_of(m_objects.begin(), m_objects.end(), [](const PrintObject *object) {
+        return object->config().belt_purge_tower_object.value;
+    });
+}
+
+// Belt mode: align ALL objects on the plate (the printed objects AND the purge
+// prism) onto one common layer grid, so the prism can absorb every toolchange.
+//
+// After belt slicing each object's layer print_z carries a per-object global z
+// offset (mesh-vertex-scan belt_z_shift + instance-Y-dependent terms), so
+// objects at different belt-Y positions get layer grids with DIFFERENT residues
+// (mod layer height). Purge marking looks absorbers up with
+// get_layer_at_printz(lt.print_z, EPSILON), so a toolchange on object B only
+// absorbs into the prism if the prism has a layer at B's print_z. Snapping only
+// the prism to one object therefore worked for a single (assembled) multi-color
+// object but failed with multiple separate objects — the prism could follow only
+// one grid, and toolchanges on the others went unabsorbed ("multiple layer
+// grids" warning).
+//
+// Fix: pick one reference grid (the tallest object) and shift every object onto
+// it. Each shift is at most half a layer height — a sub-100µm move along the
+// belt, the very same mechanism the per-object global_z_offset already uses, and
+// it keeps each object internally consistent (belt_shift_layer_grid moves the
+// object's layers, its support layers, and its belt floor together). Equal layer
+// height across objects is enforced by Print::validate(), so once residues match
+// every object steps on the same lattice {ref_offset + k*h} and every toolchange
+// layer coincides with a prism layer.
+void Print::_align_belt_purge_layers()
+{
+    PrintObject *prism = nullptr;
+    for (PrintObject *po : m_objects)
+        if (po->config().belt_purge_tower_object.value && !po->layers().empty()) {
+            prism = po;
+            break;
+        }
+    if (prism == nullptr || prism->layers().empty())
+        return;
+
+    const double h = prism->config().layer_height.value;
+    if (h <= EPSILON)
+        return;
+
+    // Grid residue of an object's layer grid: identical for all of an object's
+    // layers above the first since they step by h.
+    auto grid_offset = [h](const PrintObject *po) -> double {
+        if (po->layers().empty())
+            return 0.;
+        const double z = po->layers().front()->print_z;
+        return z - std::floor(z / h) * h; // in [0, h)
+    };
+
+    // Reference grid: the tallest non-prism object (proxy for the object with
+    // the most toolchange layers — minimizes how far the rest must move).
+    const PrintObject *ref     = nullptr;
+    double             ref_top = -std::numeric_limits<double>::max();
+    for (const PrintObject *po : m_objects) {
+        if (po->config().belt_purge_tower_object.value || po->layers().empty())
+            continue;
+        const double top = po->layers().back()->print_z;
+        if (top > ref_top) {
+            ref_top = top;
+            ref     = po;
+        }
+    }
+    if (ref == nullptr)
+        return;
+
+    const double ref_offset = grid_offset(ref);
+
+    // Snap every object (printed objects AND the prism) onto the reference grid.
+    for (PrintObject *po : m_objects) {
+        if (po->layers().empty())
+            continue;
+        double delta = ref_offset - grid_offset(po);
+        if (delta > 0.5 * h)
+            delta -= h;
+        else if (delta <= -0.5 * h)
+            delta += h;
+        po->belt_shift_layer_grid(delta); // no-op for the reference object (delta ~ 0)
+    }
+}
+
+// Belt mode replacement for _make_wipe_tower(): plan filament-change purging
+// into the belt purge prism (and any other flush_into_* object) using the
+// flush-into-objects machinery, without generating classic wipe tower G-code.
+// The toolchange itself is emitted by GCode::set_extruder() via the
+// change_filament_gcode macro; the overrides marked here make the new
+// filament's first extrusions land in the purge prism.
+void Print::_plan_belt_purge()
+{
+    m_wipe_tower_data.clear();
+
+    // psWipeTower may be invalidated without posSlice (for example after a
+    // filament-map or tool-ordering change). Restore a prism shortened by the
+    // previous plan so a newly higher toolchange can use its original layers.
+    for (PrintObject *po : m_objects)
+        if (po->config().belt_purge_tower_object.value)
+            po->belt_undo_purge_plan();
+
+    // Must run before ToolOrdering is built: LayerTools merge per-object layer
+    // print_z values, and the prism only absorbs purge where its (snapped)
+    // layers coincide with the toolchange layers.
+    this->_align_belt_purge_layers();
+
+    const unsigned int number_of_extruders = (unsigned int) m_config.filament_colour.values.size();
+
+    // No initial priming extrusions: there is no tower to prime on.
+    m_wipe_tower_data.tool_ordering = ToolOrdering(*this, (unsigned int) -1, false);
+    m_wipe_tower_data.tool_ordering.sort_and_build_data(*this, (unsigned int) -1, false);
+
+    if (m_wipe_tower_data.tool_ordering.empty() || m_wipe_tower_data.tool_ordering.last_extruder() == unsigned(-1))
+        throw Slic3r::SlicingError("The print is empty. The model is not printable with current print settings.");
+
+    // Is there any filament change at all? Not ToolOrdering::has_wipe_tower(): that reads the
+    // FIRST layer's flag, and on a belt the first layer may be a brim apron band, which carries
+    // neither object nor support and so never gets the flag even when the print changes filament.
+    {
+        bool         any_change = false;
+        unsigned int cur        = m_wipe_tower_data.tool_ordering.first_extruder();
+        for (const auto &lt : m_wipe_tower_data.tool_ordering.layer_tools())
+            for (const unsigned int e : lt.extruders)
+                if (e != cur) { any_change = true; cur = e; }
+        if (! any_change)
+            return;
+    }
+
+    this->throw_if_canceled();
+
+    // Flush volumes per filament pair, mirroring the generic wipe tower path:
+    // full flush matrix for single extruder multi material with purging enabled,
+    // plain prime volume otherwise.
+    std::vector<float> flush_matrix(cast<float>(
+        get_flush_volumes_matrix(m_config.flush_volumes_matrix.values, 0, m_config.nozzle_diameter.values.size())));
+    std::vector<std::vector<float>> wipe_volumes;
+    for (unsigned int i = 0; i < number_of_extruders; ++i)
+        wipe_volumes.push_back(std::vector<float>(flush_matrix.begin() + i * number_of_extruders,
+                                                  flush_matrix.begin() + (i + 1) * number_of_extruders));
+    const bool  use_flush_matrix = m_config.purge_in_prime_tower && m_config.single_extruder_multi_material;
+    const float flush_multiplier = (float) m_config.flush_multiplier.get_at(0);
+
+    // Cancel the purge prism early: pre-scan the tool ordering for the highest
+    // print_z that actually has a toolchange, then drop the prism's layers above
+    // it so the tower stops at the last color swap (saves filament/time). This
+    // MUST happen before the marking loop below: ensure_perimeters_infills_order
+    // force-overrides the prism's extrusions on every layer (it is a dedicated
+    // flush object), so truncating afterwards would leave dangling overrides
+    // pointing into deleted layers.
+    {
+        // The tool ordering covers the WHOLE print, and the prism is a printed
+        // object in it. Left unbounded, the scan below sees the prism's own
+        // toolchanges on layers above every model object -- the prism runs past
+        // them by design (ramp/height compensation at the tilted ends) -- so
+        // last_tc_z lands at the prism's own top and the truncation cancels
+        // nothing. The tower ends up justifying its own existence.
+        //
+        // Nothing above the tallest printed object can require a color change,
+        // so bound the scan there. On MCTEST5 that is 197 toolchanges spanning
+        // z=154.00..193.20 with the tallest object topping out at 153.80, i.e.
+        // 39.4 mm of tower that no swap ever needed.
+        // Support layers count too: on a belt they can extend above the object's
+        // own top, and a toolchange there is a real one.
+        double obj_top_z = -1.;
+        for (const PrintObject *po : m_objects) {
+            if (po->config().belt_purge_tower_object.value)
+                continue;
+            if (!po->layers().empty())
+                obj_top_z = std::max(obj_top_z, po->layers().back()->print_z);
+            if (!po->support_layers().empty())
+                obj_top_z = std::max(obj_top_z, po->support_layers().back()->print_z);
+        }
+
+        double       last_tc_z   = -1.;
+        unsigned int cur_ext     = m_wipe_tower_data.tool_ordering.first_extruder();
+        for (const auto &lt : m_wipe_tower_data.tool_ordering.layer_tools()) {
+            // layer_tools() is ordered by print_z ascending.
+            if (obj_top_z >= 0. && lt.print_z > obj_top_z + EPSILON)
+                break;
+            for (const unsigned int e : lt.extruders)
+                if (e != cur_ext) { last_tc_z = lt.print_z; cur_ext = e; }
+        }
+        // Deliberately NOT cancelling the prism outright when no object toolchange
+        // exists: belt_truncate_layers_above(0.) empties m_layers, and an object
+        // with zero layers is not something the rest of the pipeline expects. The
+        // GUI already declines to create a prism unless more than one filament is
+        // in use, so this case is a stale prism, not a hot path -- leave it whole
+        // rather than risk a zero-layer object.
+        if (last_tc_z >= 0.)
+            for (PrintObject *po : m_objects)
+                if (po->config().belt_purge_tower_object.value && !po->layers().empty()) {
+                    po->belt_truncate_layers_above(last_tc_z);
+                    break;
+                }
+    }
+
+    // The prism only absorbs purge at toolchange layers whose print_z coincides
+    // with one of its own layers.
+    PrintObject *prism_po = nullptr;
+    for (PrintObject *po : m_objects)
+        if (po->config().belt_purge_tower_object.value && !po->layers().empty()) { prism_po = po; break; }
+
+    float  total_leftover      = 0.f;
+    float  worst_layer_leftover = 0.f;
+    double worst_layer_z       = 0.;
+
+    unsigned int current_extruder_id = m_wipe_tower_data.tool_ordering.first_extruder();
+    for (auto &layer_tools : m_wipe_tower_data.tool_ordering.layer_tools()) {
+        float layer_leftover = 0.f;
+        for (const unsigned int extruder_id : layer_tools.extruders) {
+            if (extruder_id == current_extruder_id)
+                continue;
+            float volume_to_wipe = use_flush_matrix ?
+                wipe_volumes[current_extruder_id][extruder_id] * flush_multiplier :
+                (float) m_config.prime_volume;
+            float leftover = layer_tools.wiping_extrusions().mark_wiping_extrusions(*this, current_extruder_id, extruder_id,
+                                                                                    volume_to_wipe);
+            layer_leftover += leftover;
+            current_extruder_id = extruder_id;
+        }
+
+        // Plastic saving: drop the prism's fills that no toolchange on this layer
+        // claimed. At this point the prism's OVERRIDDEN fills are exactly the
+        // purge; the rest would print as solid infill in the prism's own filament
+        // for nothing -- which is the whole prism on a layer with no toolchange
+        // (141 of 692 layers on MCTEST5 before the truncation fix). Perimeters are
+        // left alone so the bar keeps a continuous wall along the belt.
+        //
+        // Non-destructive: the entities are stashed with their positions and put
+        // back by belt_restore_dropped_fills() at the top of the next plan. An
+        // earlier version deleted them outright, which broke replanning when a
+        // later tool ordering needed what this one had not claimed -- that is why
+        // it was removed rather than kept.
+        if (prism_po != nullptr) {
+            const auto &we = layer_tools.wiping_extrusions();
+            prism_po->belt_drop_unclaimed_fills(
+                prism_po->get_layer_at_printz(layer_tools.print_z, EPSILON),
+                [&we, prism_po](const ExtrusionEntity *e) { return we.is_entity_overridden(e, prism_po, 0); });
+        }
+
+        layer_tools.wiping_extrusions().ensure_perimeters_infills_order(*this);
+        if (layer_leftover > 0.f) {
+            total_leftover += layer_leftover;
+            if (layer_leftover > worst_layer_leftover) {
+                worst_layer_leftover = layer_leftover;
+                worst_layer_z        = layer_tools.print_z;
+            }
+        }
+        this->throw_if_canceled();
+    }
+
+    if (total_leftover > 1.f) {
+        this->active_step_add_warning(
+            PrintStateBase::WarningLevel::CRITICAL,
+            Slic3r::format(_u8L("The belt purge tower cannot absorb the full purge volume: %1% mm³ in total could not "
+                                "be purged (worst layer: %2% mm³ at height %3%). The print may show color bleeding. "
+                                "Increase the belt purge tower width, or reduce flushing volumes."),
+                           int(std::ceil(total_leftover)), int(std::ceil(worst_layer_leftover)),
+                           Slic3r::float_to_string_decimal_point(worst_layer_z, 2)));
+    }
+}
+
+// Belt mode: shift the sliced layer grid by delta. Mirrors the global_z_offset
+// application in slice() — layer print_z and belt_floor_z_shift move together
+// so belt floor clipping stays consistent with the shifted grid. Used by
+// Print::_align_belt_purge_layers() to snap the purge prism onto the printed
+// objects' layer grid; |delta| <= half a layer height, i.e. a sub-layer shift
+// of the prism along the belt.
+void PrintObject::belt_shift_layer_grid(double delta)
+{
+    if (std::abs(delta) < EPSILON)
+        return;
+    for (Layer *layer : m_layers)
+        layer->print_z += delta;
+    for (SupportLayer *layer : m_support_layers)
+        layer->print_z += delta;
+    // The brim's apron bands below the first layer carry their own print_z.
+    for (BeltBrimBand &band : m_belt_brim_prologue)
+        band.print_z += delta;
+    m_slicing_params.belt_floor_z_shift += delta;
+    // The grid stays shifted across a support-only or brim-only change (posSlice does
+    // not rerun), so everything slice() derived from it has to follow: the cached floor
+    // that update_slicing_parameters() restores, and the global offset the organic
+    // support layers and the adaptive infill octree are placed with. Left alone, the
+    // next alignment finds a delta of 0 and the floor and the supports sit up to half
+    // a layer off the grid, unlike a fresh slice.
+    if (m_belt_floor_z_shift_cache_valid)
+        m_belt_floor_z_shift_cached += delta;
+    m_belt_global_z_offset += delta;
+}
+
+// Belt mode: drop layers strictly above z (used to cancel the purge prism early
+// once there are no more toolchanges above z, so the tower stops at the last
+// color swap instead of wasting filament up the rest of the belt). Each layer's
+// cross-section is already sliced, so removing upper layers does not affect the
+// last toolchange's coverage. Deletes the Layer objects and clears the new top
+// layer's upper-layer link. Returns the number of layers removed.
+size_t PrintObject::belt_truncate_layers_above(coordf_t z)
+{
+    // A repeated plan always starts from the restored full layer set.
+    assert(m_belt_truncated_layers.empty());
+    size_t keep = m_layers.size();
+    while (keep > 0 && m_layers[keep - 1]->print_z > z + EPSILON)
+        --keep;
+    if (keep >= m_layers.size())
+        return 0;
+    const size_t removed = m_layers.size() - keep;
+    m_belt_truncated_layers.assign(m_layers.begin() + keep, m_layers.end());
+    m_layers.resize(keep);
+    if (!m_layers.empty())
+        m_layers.back()->upper_layer = nullptr;
+    return removed;
+}
+
+// Plastic saving on the purge prism: keep only the fills a toolchange claimed.
+//
+// Called per layer from _plan_belt_purge(), after the real-purge marking and
+// BEFORE ensure_perimeters_infills_order() -- that pass force-overrides every
+// remaining fill on the prism (it is a dedicated flush object), so afterwards
+// everything looks claimed and nothing could be distinguished.
+size_t PrintObject::belt_drop_unclaimed_fills(Layer *layer, const std::function<bool(const ExtrusionEntity*)> &claimed)
+{
+    if (layer == nullptr)
+        return 0;
+    size_t dropped = 0;
+    for (size_t ri = 0; ri < layer->regions().size(); ++ri) {
+        LayerRegion *lr = layer->get_region(ri);
+        auto        &ents = lr->fills.entities;
+        ExtrusionEntitiesPtr keep;
+        keep.reserve(ents.size());
+        for (size_t i = 0; i < ents.size(); ++i) {
+            if (claimed(ents[i])) {
+                keep.emplace_back(ents[i]);
+            } else {
+                // Stash with its original index so the restore is exact.
+                m_belt_dropped_fills.push_back(BeltDroppedFill{ layer, ri, i, ents[i] });
+                ++dropped;
+            }
+        }
+        ents = std::move(keep);
+    }
+    return dropped;
+}
+
+void PrintObject::belt_restore_dropped_fills()
+{
+    if (m_belt_dropped_fills.empty())
+        return;
+    // Ascending index per (layer, region): inserting in that order lands every
+    // entity back at its original position, because each insertion shifts only
+    // the entries after it, which are themselves still to be inserted.
+    std::stable_sort(m_belt_dropped_fills.begin(), m_belt_dropped_fills.end(),
+                     [](const BeltDroppedFill &a, const BeltDroppedFill &b) {
+                         if (a.layer != b.layer)           return a.layer < b.layer;
+                         if (a.region_idx != b.region_idx) return a.region_idx < b.region_idx;
+                         return a.index < b.index;
+                     });
+    for (const BeltDroppedFill &d : m_belt_dropped_fills) {
+        auto &ents = d.layer->get_region(d.region_idx)->fills.entities;
+        ents.insert(ents.begin() + std::min(d.index, ents.size()), d.entity);
+    }
+    m_belt_dropped_fills.clear();
+}
+
+void PrintObject::belt_restore_truncated_layers()
+{
+    if (m_belt_truncated_layers.empty())
+        return;
+
+    m_layers.insert(m_layers.end(), m_belt_truncated_layers.begin(), m_belt_truncated_layers.end());
+    m_belt_truncated_layers.clear();
+    for (size_t i = 0; i < m_layers.size(); ++i) {
+        m_layers[i]->lower_layer = i == 0 ? nullptr : m_layers[i - 1];
+        m_layers[i]->upper_layer = i + 1 < m_layers.size() ? m_layers[i + 1] : nullptr;
+    }
+}
+
+} // namespace Slic3r
@@ -0,0 +1,70 @@
+#include "BeltSliceStrategy.hpp"
+#include "Model.hpp"
+#include "BeltTransform.hpp"
+#include "Point.hpp"
+#include "PrintConfig.hpp"
+
+#include <limits>
+#include <algorithm>
+
+namespace Slic3r {
+
+void BeltSliceStrategy::apply_preslice_transforms(Transform3d           &trafo,
+                                                  const PrintConfig     &config,
+                                                  const ModelVolumePtrs &model_volumes,
+                                                  double                *out_belt_min_z)
+{
+    // 1. Standalone pre-slice axis remap (works without belt mode).
+    const bool has_remap = BeltTransformPipeline::has_preslice_remap(config);
+    if (has_remap)
+        trafo = BeltTransformPipeline::build_preslice_remap(config) * trafo;
+
+    // 2. Belt rotation — the sole mesh-side belt transform (matching
+    //    BeltTransformPipeline::build_forward_transform).  Only active in
+    //    belt-printer mode.
+    bool has_rotation = false;
+    if (config.belt_printer.value) {
+        const Matrix3d rot = BeltTransformPipeline::build_rotation_matrix(config, &has_rotation);
+        if (has_rotation) {
+            Transform3d belt_xform = Transform3d::Identity();
+            belt_xform.linear() = rot;
+            trafo = belt_xform * trafo;
+        }
+    }
+
+    if (!has_remap && !has_rotation)
+        return;
+
+    // 3. Z-shift — detect if the mesh clips below the build plate after the
+    // transforms and lift it.  Each mesh vertex must be brought into object space
+    // via mv->get_matrix() before applying the full trafo (which is in object
+    // space).  Missing this on assemblies (where per-volume get_matrix() positions
+    // each volume within the object) would compute min_z against mesh-local vertex
+    // coordinates rather than object-space coordinates, so volumes translated along
+    // the slicer's Z axis would be silently excluded from the bound check.
+
+    double min_z = std::numeric_limits<double>::max();
+    for (const ModelVolume *mv : model_volumes) {
+        if (!mv->is_model_part()) continue;
+        Transform3d vol_trafo = trafo * mv->get_matrix();
+        const auto &its = mv->mesh().its;
+        for (const stl_vertex &v : its.vertices) {
+            Vec3d vm = v.cast<double>();
+            Vec3d pt = vol_trafo * vm;
+            min_z = std::min(min_z, pt.z());
+        }
+    }
+    const double z_shift_val = (min_z < 0. && min_z != std::numeric_limits<double>::max()) ? -min_z : 0.;
+    if (z_shift_val > 0.) {
+        Transform3d z_shift = Transform3d::Identity();
+        z_shift.matrix()(2, 3) = z_shift_val;
+        trafo = z_shift * trafo;
+    }
+    // out_belt_min_z is only meaningful in belt mode; the standalone-remap path
+    // never reported it.
+    if (out_belt_min_z && config.belt_printer.value) {
+        *out_belt_min_z = (min_z != std::numeric_limits<double>::max()) ? min_z : 0.;
+    }
+}
+
+} // namespace Slic3r
@@ -0,0 +1,36 @@
+#pragma once
+
+#include "libslic3r.h"
+#include "Point.hpp"
+#include "BeltTransform.hpp"
+#include "PrintConfig.hpp"
+#include "Model.hpp"
+
+namespace Slic3r {
+
+// Belt printer / pre-slice transform strategy.
+//
+// Composes, in order, the pre-slice mesh transforms applied before slicing:
+//   1. Pre-slice axis remap (standalone — works without belt mode)
+//   2. Belt rotation (the sole mesh-side belt transform; shear & scale are a
+//      g-code-side stage, see MachineFrameTransform)
+//   3. Per-object Z-shift that lifts the mesh above the build plate
+//
+// Isolates this belt/remap-specific logic from the generic slicing pipeline in
+// PrintObjectSlice.cpp.
+class BeltSliceStrategy
+{
+public:
+    // Apply the pre-slice remap + belt rotation + Z-shift to `trafo` in place.
+    // No-op when neither a remap nor a belt rotation is configured.
+    //
+    // out_belt_min_z (if non-null) receives the minimum mesh Z after the
+    // transforms, but only in belt-printer mode — the standalone-remap path
+    // never reported it.
+    static void apply_preslice_transforms(Transform3d           &trafo,
+                                          const PrintConfig     &config,
+                                          const ModelVolumePtrs &model_volumes,
+                                          double                *out_belt_min_z = nullptr);
+};
+
+} // namespace Slic3r
@@ -0,0 +1,230 @@
+#include "BeltTransform.hpp"
+#include "Model.hpp"
+#include "BoundingBox.hpp"
+#include "Config.hpp"
+#include "Geometry.hpp"
+#include "Point.hpp"
+#include "PrintConfig.hpp"
+#include "libslic3r.h"
+
+#include <limits>
+#include <algorithm>
+#include <cmath>
+#include <cstdlib>
+
+namespace Slic3r {
+
+// ---- Matrix builders ------------------------------------------------------
+
+Transform3d BeltTransformPipeline::build_preslice_remap(const PrintConfig &config)
+{
+    Transform3d pre_remap = Transform3d::Identity();
+    if (!has_preslice_remap(config))
+        return pre_remap;
+
+    int pre_rx = int(config.preslice_remap_x.value);
+    int pre_ry = int(config.preslice_remap_y.value);
+    int pre_rz = int(config.preslice_remap_z.value);
+
+    // Each remap value selects a source axis and sign.
+    auto remap_column = [](int r) -> Vec3d {
+        int axis = r % 3;
+        Vec3d col = Vec3d::Zero();
+        if (r < 3)      col[axis] =  1.0;  // +axis
+        else if (r < 6) col[axis] = -1.0;  // -axis
+        else            col[axis] = -1.0;  // Rev: max - pos = -(pos - max)
+        return col;
+    };
+
+    Matrix3d remap_lin;
+    remap_lin.col(0) = remap_column(pre_rx);
+    remap_lin.col(1) = remap_column(pre_ry);
+    remap_lin.col(2) = remap_column(pre_rz);
+    pre_remap.linear() = remap_lin;
+
+    // Translation for Rev modes (needs build volume extents).
+    if (pre_rx >= 6 || pre_ry >= 6 || pre_rz >= 6) {
+        BoundingBoxf bbox_bed(config.printable_area.values);
+        Vec3d vol_max(bbox_bed.max.x(), bbox_bed.max.y(),
+                      config.printable_height.value);
+        Vec3d remap_trans = Vec3d::Zero();
+        auto add_rev = [&](int r, int out) {
+            if (r >= 6) remap_trans[out] = vol_max[r % 3];
+        };
+        add_rev(pre_rx, 0);
+        add_rev(pre_ry, 1);
+        add_rev(pre_rz, 2);
+        pre_remap.translation() = remap_trans;
+    }
+
+    return pre_remap;
+}
+
+Matrix3d BeltTransformPipeline::build_rotation_matrix(const PrintConfig &config, bool *has_rot_out)
+{
+    BeltRotationAxis axis = config.belt_slice_rotation.value;
+    double angle_deg = config.belt_slice_rotation_angle.value;
+    bool active = axis != BeltRotationAxis::None && std::abs(angle_deg) > EPSILON;
+    if (has_rot_out) *has_rot_out = active;
+    if (!active)
+        return Matrix3d::Identity();
+    double angle_rad = Geometry::deg2rad(angle_deg);
+    Vec3d unit_axis;
+    switch (axis) {
+    case BeltRotationAxis::X: unit_axis = Vec3d::UnitX(); break;
+    case BeltRotationAxis::Y: unit_axis = Vec3d::UnitY(); break;
+    case BeltRotationAxis::Z: unit_axis = Vec3d::UnitZ(); break;
+    default:                  return Matrix3d::Identity();
+    }
+    return Eigen::AngleAxisd(angle_rad, unit_axis).toRotationMatrix();
+}
+
+Transform3d BeltTransformPipeline::build_forward_transform(const PrintConfig &config)
+{
+    // Mesh-side belt transform: rotation applied after the pre-slice axis remap.
+    // (Shear & scale are a g-code-side stage, not part of the mesh transform.)
+    Transform3d pre_remap = build_preslice_remap(config);
+    Matrix3d    rot       = build_rotation_matrix(config);
+
+    Transform3d combined = Transform3d::Identity();
+    combined.linear() = rot;
+    combined = combined * pre_remap;
+    return combined;
+}
+
+// ---- Bounding box remap ---------------------------------------------------
+
+BoundingBoxf3 BeltTransformPipeline::remap_bbox(const BoundingBoxf3 &bb, const PrintConfig &config)
+{
+    if (!has_preslice_remap(config))
+        return bb;  // Identity remap, or belt mode off.
+
+    int pre_rx = int(config.preslice_remap_x.value);
+    int pre_ry = int(config.preslice_remap_y.value);
+    int pre_rz = int(config.preslice_remap_z.value);
+
+    auto remap_coord = [](int r, const Vec3d &v) -> double {
+        int axis = r % 3;
+        if (r < 3) return v[axis];
+        return -v[axis];
+    };
+
+    Vec3d mn = bb.min.cast<double>(), mx = bb.max.cast<double>();
+    BoundingBoxf3 rbb;
+    for (int i = 0; i < 8; ++i) {
+        Vec3d c((i & 1) ? mx.x() : mn.x(),
+                (i & 2) ? mx.y() : mn.y(),
+                (i & 4) ? mx.z() : mn.z());
+        Vec3d rc(remap_coord(pre_rx, c), remap_coord(pre_ry, c), remap_coord(pre_rz, c));
+        if (i == 0) rbb = BoundingBoxf3(rc, rc);
+        else rbb.merge(rc);
+    }
+    return rbb;
+}
+
+BoundingBoxf3 BeltTransformPipeline::remap_bbox(const ModelObject &model_object, const PrintConfig &config)
+{
+    return remap_bbox(model_object.raw_bounding_box(), config);
+}
+
+// ---- Belt floor parameters ------------------------------------------------
+
+// Shared implementation for both PrintConfig and DynamicPrintConfig.
+// Template avoids duplicating the math for the two config types.
+namespace {
+
+template<typename Config>
+BeltTransformPipeline::BeltHeightResult compute_belt_height_and_floor_impl(
+    const Config &config, const BoundingBoxf3 &bb, double original_height)
+{
+    BeltTransformPipeline::BeltHeightResult result;
+    result.object_height = original_height;
+
+    // Extract the mesh rotation from config (the sole mesh-side belt transform).
+    BeltRotationAxis rot_axis;
+    double           rot_angle;
+
+    if constexpr (std::is_same_v<Config, PrintConfig>) {
+        rot_axis  = config.belt_slice_rotation.value;
+        rot_angle = config.belt_slice_rotation_angle.value;
+    } else {
+        // DynamicPrintConfig path
+        auto get_float = [&](const char *key) {
+            auto *opt = config.template option<ConfigOptionFloat>(key);
+            return opt ? opt->value : 0.0;
+        };
+        auto get_rot_axis = [&](const char *key) {
+            auto *opt = config.template option<ConfigOptionEnum<BeltRotationAxis>>(key);
+            return opt ? opt->value : BeltRotationAxis::None;
+        };
+        rot_axis  = get_rot_axis("belt_slice_rotation");
+        rot_angle = get_float("belt_slice_rotation_angle");
+    }
+
+    bool has_rotation = rot_axis != BeltRotationAxis::None && std::abs(rot_angle) > EPSILON;
+    if (!has_rotation)
+        return result;
+
+    // Rotation path: sweep the 8 bbox corners through R to get the rotated height,
+    // then derive the belt floor (the image of machine-Z = 0 under R).
+    double angle_rad = Geometry::deg2rad(rot_angle);
+    Vec3d unit_axis;
+    switch (rot_axis) {
+    case BeltRotationAxis::X: unit_axis = Vec3d::UnitX(); break;
+    case BeltRotationAxis::Y: unit_axis = Vec3d::UnitY(); break;
+    case BeltRotationAxis::Z: unit_axis = Vec3d::UnitZ(); break;
+    default:                  unit_axis = Vec3d::UnitX(); break;
+    }
+    Matrix3d R = Eigen::AngleAxisd(angle_rad, unit_axis).toRotationMatrix();
+    double min_rz = std::numeric_limits<double>::max();
+    double max_rz = std::numeric_limits<double>::lowest();
+    for (int i = 0; i < 8; ++i) {
+        Vec3d c((i & 1) ? bb.max.x() : bb.min.x(),
+                (i & 2) ? bb.max.y() : bb.min.y(),
+                (i & 4) ? bb.max.z() : bb.min.z());
+        double z = (R * c).z();
+        min_rz = std::min(min_rz, z);
+        max_rz = std::max(max_rz, z);
+    }
+    result.object_height = max_rz - min_rz;
+
+    // Belt floor in slicer-frame is the image of z_machine = 0 under R.
+    //   R(+α, X): point (·, y, 0) → (·, cos α · y, sin α · y) ⇒ z = tan(α) · y_s
+    //   R(+α, Y): point (x, ·, 0) → (cos α · x, ·, -sin α · x) ⇒ z = -tan(α) · x_s
+    //   R(+α, Z): point (·, ·, 0) → (·, ·, 0); no tilt → no floor
+    double sin_a = std::sin(angle_rad), cos_a = std::cos(angle_rad);
+    switch (rot_axis) {
+    case BeltRotationAxis::X:
+        result.floor_params.shear_factor = (std::abs(cos_a) > EPSILON) ?  sin_a / cos_a : 0.;
+        result.floor_params.from_axis    = 1; // Y
+        break;
+    case BeltRotationAxis::Y:
+        result.floor_params.shear_factor = (std::abs(cos_a) > EPSILON) ? -sin_a / cos_a : 0.;
+        result.floor_params.from_axis    = 0; // X
+        break;
+    case BeltRotationAxis::Z:
+    default:
+        result.floor_params.shear_factor = 0.0;
+        result.floor_params.from_axis    = 1;
+        break;
+    }
+    result.floor_params.z_shift = bb.min.z() + ((min_rz < 0.) ? -min_rz : 0.);
+
+    return result;
+}
+
+} // anonymous namespace
+
+BeltTransformPipeline::BeltHeightResult BeltTransformPipeline::compute_belt_height_and_floor(
+    const PrintConfig &config, const BoundingBoxf3 &remapped_bbox, double original_height)
+{
+    return compute_belt_height_and_floor_impl(config, remapped_bbox, original_height);
+}
+
+BeltTransformPipeline::BeltHeightResult BeltTransformPipeline::compute_belt_height_and_floor(
+    const DynamicPrintConfig &config, const BoundingBoxf3 &remapped_bbox, double original_height)
+{
+    return compute_belt_height_and_floor_impl(config, remapped_bbox, original_height);
+}
+
+} // namespace Slic3r
@@ -0,0 +1,168 @@
+#pragma once
+
+#include "libslic3r.h"
+#include "Point.hpp"
+#include "BoundingBox.hpp"
+#include "PrintConfig.hpp"
+#include "Geometry.hpp"
+#include "Config.hpp"
+
+#include <cmath>
+
+namespace Slic3r {
+
+class ModelObject;
+
+// Shared belt-printer transform math.
+//
+// The pre-slice pipeline applied in PrintObjectSlice.cpp is:
+//     trafo_out = z_shift * rotation * pre_remap * trafo_in
+//
+// Rotation is the sole mesh-side belt transform; shear & scale are applied
+// to the g-code instead (see MachineFrameTransform).  This class provides the
+// building blocks so every call site uses the same implementation.  z_shift is
+// object-dependent (computed from mesh vertex bounds) and is NOT included in
+// build_forward_transform().  The machine-frame shear/scale is derived directly
+// from the tilt angle in MachineFrameTransform and no longer lives here.
+//
+// Design note: this mesh-rotation approach replaced an earlier pre-shear
+// method (now removed).  While that initial pre-shear method was instrumental
+// in getting belt printer slicing off the ground in the first place, its place is
+// in the past.  A big thank you goes to the Unlayered3D team, who recommended 
+// switching to a pre-slice rotation stage instead.  Doing so keeps the slicing 
+// operation isometric — no distortion of the sliced geometry — while the 
+// non-orthogonal machine-axis compensation is confined to a g-code-side shear/scale
+// derived from the same tilt angle.
+// 
+// This fixed a number of issues, including several issues noticed by hotcubcar
+// regarding adaptive infills not working, gyroid becoming anisotropic, and more 
+// that were all mostly resolved as a result of the switch.
+// 
+// This also means that the pre-slice rotation transform methodology can be used 
+// more cleanly on non-belt printers.
+// - HarrierPigeon (Joseph Robertson)
+
+class BeltTransformPipeline
+{
+public:
+    // ---- Identity checks --------------------------------------------------
+
+    // Whether the axis remaps (preslice_remap_* and gcode_remap_*) apply at all.
+    // The remap fields are only offered in the belt printer group, so a value
+    // left in a profile must not change a non-belt print: with belt mode off every
+    // belt-only key is a no-op. This is the one place to widen if a non-belt use
+    // ever needs them.
+    static bool axis_remap_enabled(const PrintConfig &config) { return config.belt_printer.value; }
+    static bool axis_remap_enabled(const DynamicPrintConfig &config)
+    {
+        auto *opt = config.option<ConfigOptionBool>("belt_printer");
+        return opt != nullptr && opt->value;
+    }
+
+    static bool has_preslice_remap(const PrintConfig &config)
+    {
+        return axis_remap_enabled(config) &&
+              (int(config.preslice_remap_x.value) != int(RemapAxis::PosX) ||
+               int(config.preslice_remap_y.value) != int(RemapAxis::PosY) ||
+               int(config.preslice_remap_z.value) != int(RemapAxis::PosZ));
+    }
+
+    // Overload accepting DynamicPrintConfig (used in static slicing_parameters).
+    static bool has_preslice_remap(const DynamicPrintConfig &config)
+    {
+        if (! axis_remap_enabled(config))
+            return false;
+        auto get_int = [&](const char *key) -> int {
+            auto *opt = config.option<ConfigOptionEnum<RemapAxis>>(key);
+            return opt ? int(opt->value) : 0;
+        };
+        return get_int("preslice_remap_x") != int(RemapAxis::PosX) ||
+               get_int("preslice_remap_y") != int(RemapAxis::PosY) ||
+               get_int("preslice_remap_z") != int(RemapAxis::PosZ);
+    }
+
+    static bool has_rotation(const PrintConfig &config)
+    {
+        return config.belt_slice_rotation.value != BeltRotationAxis::None &&
+               std::abs(config.belt_slice_rotation_angle.value) > EPSILON;
+    }
+
+    // Physical belt tilt derived from the slicing rotation — the single source of
+    // truth for bed rendering, support gravity tilt and the bed-exclusion
+    // projection.  Returns the tilt magnitude in degrees split onto the X and Y
+    // build-plate tilt axes according to the rotation axis:
+    //   rotation about X  → tilt_x = angle   (gantry tilts in the YZ plane)
+    //   rotation about Y  → tilt_y = angle   (gantry tilts in the XZ plane)
+    //   rotation about Z / None → no tilt    (in-plane spin doesn't tilt the belt)
+    // The magnitude uses abs(angle) so a negative rotation still reports a positive
+    // physical tilt.
+    struct PhysicalTilt { double tilt_x_deg = 0.; double tilt_y_deg = 0.; };
+
+    static PhysicalTilt physical_tilt(BeltRotationAxis axis, double angle_deg)
+    {
+        PhysicalTilt t;
+        double mag = std::abs(angle_deg);
+        switch (axis) {
+        case BeltRotationAxis::X: t.tilt_x_deg = mag; break;
+        case BeltRotationAxis::Y: t.tilt_y_deg = mag; break;
+        default: break; // Z / None: no physical tilt
+        }
+        return t;
+    }
+
+    static PhysicalTilt physical_tilt(const PrintConfig &config)
+    {
+        return physical_tilt(config.belt_slice_rotation.value,
+                             config.belt_slice_rotation_angle.value);
+    }
+
+    // ---- Matrix builders --------------------------------------------------
+
+    // Build the pre-slice axis remap transform (includes Rev-mode translation).
+    static Transform3d build_preslice_remap(const PrintConfig &config);
+
+    // Build the 3x3 rotation matrix from belt_slice_rotation* config.
+    // Returns Identity if rotation axis is None or angle is ~0.
+    // Also sets has_rot_out if non-null.
+    static Matrix3d build_rotation_matrix(const PrintConfig &config, bool *has_rot_out = nullptr);
+
+    // Combined forward transform (rotation * pre_remap) — the mesh-side belt
+    // transform that BeltSliceStrategy applies and BeltBackTransform inverts.
+    // Does NOT include the per-object Z-shift.
+    static Transform3d build_forward_transform(const PrintConfig &config);
+
+    // ---- Bounding box remap -----------------------------------------------
+
+    // Remap a bounding box through the pre-slice axis remap.
+    // Returns the original bbox if remap is identity.
+    static BoundingBoxf3 remap_bbox(const BoundingBoxf3 &bb, const PrintConfig &config);
+    static BoundingBoxf3 remap_bbox(const ModelObject &model_object, const PrintConfig &config);
+
+    // ---- Belt floor parameters --------------------------------------------
+
+    struct BeltFloorParams {
+        double shear_factor = 0.0;
+        int    from_axis    = 1;
+        double z_shift      = 0.0;
+    };
+
+    // Result of computing belt height + floor params.
+    struct BeltHeightResult {
+        double          object_height;  // Effective object height after shear/scale
+        BeltFloorParams floor_params;
+    };
+
+    // Compute effective object height and belt floor parameters from config
+    // and pre-remapped bounding box.  original_height is the input height
+    // (bb.size().z() or model_object.max_z()).
+    static BeltHeightResult compute_belt_height_and_floor(
+        const PrintConfig &config, const BoundingBoxf3 &remapped_bbox,
+        double original_height);
+
+    // Overload for DynamicPrintConfig (used by static slicing_parameters).
+    static BeltHeightResult compute_belt_height_and_floor(
+        const DynamicPrintConfig &config, const BoundingBoxf3 &remapped_bbox,
+        double original_height);
+};
+
+} // namespace Slic3r
@@ -474,7 +474,9 @@ static ExPolygons outer_inner_brim_area(const Print& print,
            const bool         use_brim_ears = object->config().brim_type == btPainted;
            const bool         use_inner_brim_ears = (use_auto_brim_ears || use_brim_ears) && !object->config().brim_ears_outer_only.value;
            const bool         has_inner_brim = brim_type == btInnerOnly || brim_type == btOuterAndInner || use_inner_brim_ears;
-            const bool         has_outer_brim = brim_type == btOuterOnly || brim_type == btOuterAndInner || brim_type == btAutoBrim || use_auto_brim_ears || use_brim_ears;
+            // btLeadingEdgeOnly is a belt-printer mode; on a flat bed there is no leading
+            // edge, so it degrades to an ordinary outer brim rather than silently to none.
+            const bool         has_outer_brim = brim_type == btOuterOnly || brim_type == btOuterAndInner || brim_type == btAutoBrim || brim_type == btLeadingEdgeOnly || use_auto_brim_ears || use_brim_ears;
            coord_t            ear_detection_length = scale_(object->config().brim_ears_detection_length.value);
            coordf_t           brim_ears_max_angle = object->config().brim_ears_max_angle.value;
            //ORCA: Select brim base slices from EFC-compensated outline when enabled.
@@ -889,6 +891,17 @@ void make_brim(const Print& print, PrintTryCancel try_cancel, Polygons& islands_
    std::vector<unsigned int>& printExtruders,
    std::map<ObjectInstanceID, ExPolygons>* objectBrimAreasByInstanceOut)
 {
+    // Belt printers never use the flat plate brim.
+    //
+    // With a tilted belt the brim has to be laid onto the belt plane over many layers,
+    // which BeltBrim.cpp does during posSupportMaterial.  With an untilted belt this
+    // could in principle fall through and produce an ordinary brim, but it would never
+    // reach the G-code: the plate brim is emitted out of skirt_brim_groups(), which
+    // _make_skirt() builds, and that returns early for every belt printer.  Running the
+    // generator anyway would just burn time on geometry nobody prints.
+    if (print.config().belt_printer.value)
+        return;
+
    std::map<ObjectInstanceID, ExPolygons> brimAreaMap;
    Flow                 flow = print.brim_flow();
    ExPolygons           islands_area_ex = outer_inner_brim_area(print,
@@ -84,7 +84,7 @@ public:
    indexed_triangle_set        bounding_mesh(bool scale=true) const;

    // Center of the print bed, unscaled.
-    Vec2d                       bed_center()        const { return to_2d(m_bboxf.center()); }
+    Vec2d                       bed_center()        const { return get_extents(m_bed_shape).center(); }
    // Convex hull of polygon(), scaled.
    const Polygon&              convex_hull()       const { return m_convex_hull; }
    // Smallest enclosing circle of polygon(), scaled.
@@ -85,6 +85,17 @@ set(lisbslic3r_sources
    BoundingBox.hpp
    BridgeDetector.cpp
    BridgeDetector.hpp
+    BeltBrim.cpp
+    BeltBrim.hpp
+    BeltGCode.cpp
+    BeltGCode.hpp
+    BeltPurge.cpp
+    BeltSliceStrategy.cpp
+    BeltSliceStrategy.hpp
+    BeltTransform.cpp
+    BeltTransform.hpp
+    FirstLayerPlane.cpp
+    FirstLayerPlane.hpp
    Brim.cpp
    BrimEarsPoint.hpp
    Brim.hpp
@@ -232,6 +243,14 @@ set(lisbslic3r_sources
    GCode/AdaptivePAProcessor.hpp
    GCode/AvoidCrossingPerimeters.cpp
    GCode/AvoidCrossingPerimeters.hpp
+    GCode/BeltBackTransform.cpp
+    GCode/BeltBackTransform.hpp
+    GCode/MachineFrameTransform.cpp
+    GCode/MachineFrameTransform.hpp
+    GCode/BeltKinematics.cpp
+    GCode/BeltKinematics.hpp
+    GCode/MachineKinematics.cpp
+    GCode/MachineKinematics.hpp
    GCode/ConflictChecker.cpp
    GCode/ConflictChecker.hpp
    GCode/CoolingBuffer.cpp
@@ -456,6 +475,8 @@ set(lisbslic3r_sources
    SlicingAdaptive.hpp
    Slicing.cpp
    Slicing.hpp
+    Support/BeltFloorContext.cpp
+    Support/BeltFloorContext.hpp
    Support/SupportCommon.cpp
    Support/SupportCommon.hpp
    Support/SupportLayer.hpp
@@ -403,6 +403,11 @@ inline void translate(ExPolygons &expolys, const Point &p) {
        expoly.translate(p);
 }

+inline void translate(Polygons &polys, const Point &p) {
+    for (Polygon &poly : polys)
+        poly.translate(p);
+}
+
 inline void polygons_append(Polygons &dst, const ExPolygon &src) 
 { 
    dst.reserve(dst.size() + src.holes.size() + 1);
@@ -0,0 +1,229 @@
+#include "FirstLayerPlane.hpp"
+#include "BeltTransform.hpp"
+#include "BoundingBox.hpp"
+#include "Point.hpp"
+#include "PrintConfig.hpp"
+#include "libslic3r.h"
+
+#include <algorithm>
+#include <climits>
+#include <cmath>
+
+namespace Slic3r {
+
+namespace {
+
+// Build the row of the gcode-axis-remap matrix R that produces machine_Z,
+// AS A FUNCTION OF a slicing-frame point in the GCode generator's coordinate
+// space.  Without back-transform this is just R.row(2).  With back-transform
+// the writer applies F^-1 before R, so the effective row is (R * F^-1).row(2).
+//
+// Returns a pair (gradient, constant) such that:
+//     machine_Z(p_slicing) = gradient.dot(p_slicing) + constant
+struct MachineZAffine {
+    Vec3d  gradient = Vec3d::UnitZ();
+    double constant = 0.0;
+};
+
+MachineZAffine compute_machine_z_affine(const PrintConfig &config)
+{
+    MachineZAffine out;
+
+    // R is the matrix form of GCodeWriter::apply_axis_remap.  Each output axis
+    // i picks one slicing-frame component (with sign + optional Rev mode
+    // translation) based on m_remap_{x,y,z}.  We only need row 2 (the z output)
+    // since machine_Z is what defines the first-layer plane.
+    int rz = int(config.gcode_remap_z.value);
+    int axis = rz % 3;
+    double sign;
+    double trans;
+    if (rz < int(RemapAxis::NegX)) {            // 0..2 = PosX/Y/Z
+        sign  = 1.0;
+        trans = 0.0;
+    } else if (rz < int(RemapAxis::RevX)) {     // 3..5 = NegX/Y/Z
+        sign  = -1.0;
+        trans = 0.0;
+    } else {                                     // 6..8 = RevX/Y/Z
+        sign = -1.0;
+        BoundingBoxf bbox_bed(config.printable_area.values);
+        Vec3d vol_max(bbox_bed.max.x(),
+                      bbox_bed.max.y(),
+                      config.printable_height.value);
+        trans = vol_max[axis];
+    }
+
+    Vec3d r_row = Vec3d::Zero();
+    r_row[axis] = sign;
+
+    // Without back-transform, machine_Z(slicing) = r_row · slicing + trans.
+    out.gradient = r_row;
+    out.constant = trans;
+
+    if (config.gcode_back_transform.value && config.belt_printer.value) {
+        // BeltKinematics applies F^-1 before R when back-transform is on.
+        // So machine_Z(slicing) = r_row · (F^-1 · slicing) + trans
+        //                       = (r_row^T · F^-1) · slicing + trans
+        // We need to compose r_row with F^-1 from the LEFT (treating r_row as
+        // a row vector).  Eigen makes this easy: it's just F^-1.transpose() * r_row.
+        Transform3d forward = BeltTransformPipeline::build_forward_transform(config);
+        Transform3d inverse = forward.inverse();
+        // Note: forward.translation() is normally zero (per-print transforms
+        // don't add a translation; the per-object z_shift is added separately
+        // in PrintObjectSlice).  We still incorporate inverse.translation() in
+        // case a Rev-mode preslice_remap puts a translation in F.
+        Vec3d composed_grad = inverse.linear().transpose() * r_row;
+        double composed_trans =
+            r_row.dot(inverse.translation()) + trans;
+        out.gradient = composed_grad;
+        out.constant = composed_trans;
+    }
+
+    return out;
+}
+
+} // namespace
+
+FirstLayerPlane::FirstLayerPlane(const PrintConfig &config)
+{
+    // -------- Resolve Auto -------------------------------------------------
+    FirstLayerPlaneMode mode = config.first_layer_plane.value;
+    if (mode == FirstLayerPlaneMode::Auto) {
+        bool belt_affine_active = config.belt_printer.value &&
+            config.belt_slice_rotation.value != BeltRotationAxis::None &&
+            std::abs(config.belt_slice_rotation_angle.value) > EPSILON;
+        mode = belt_affine_active ? FirstLayerPlaneMode::BeltAffine
+                                  : FirstLayerPlaneMode::XY;
+    }
+    m_mode = mode;
+
+    // -------- Band thickness ----------------------------------------------
+    // Note: layer_height lives in PrintObjectConfig, not PrintConfig, so we
+    // can't fall back to it from here.  initial_layer_print_height is in
+    // PrintConfig and is the right default anyway (the legacy first-layer
+    // semantics used initial_layer_print_height, not the regular one).
+    double thickness = config.first_layer_plane_thickness.value;
+    if (thickness <= 0.0)
+        thickness = config.initial_layer_print_height.value;
+    if (thickness <= 0.0)
+        thickness = 0.2;
+    m_thickness_mm = thickness;
+
+    const double user_offset = config.first_layer_plane_offset.value;
+
+    // -------- Build the plane ---------------------------------------------
+    auto set_axis_aligned = [&](const Vec3d &n_unit, double offset_along_n) {
+        m_normal = n_unit;
+        m_offset = offset_along_n;
+    };
+
+    switch (mode) {
+    case FirstLayerPlaneMode::XY:
+        // Legacy XY plane.  Inactive: short-circuit to layer-index path.
+        set_axis_aligned(Vec3d::UnitZ(), user_offset);
+        m_active = false;
+        return;
+
+    case FirstLayerPlaneMode::YZ:
+        set_axis_aligned(Vec3d::UnitX(), user_offset);
+        m_active = true;
+        return;
+
+    case FirstLayerPlaneMode::XZ:
+        set_axis_aligned(Vec3d::UnitY(), user_offset);
+        m_active = true;
+        return;
+
+    case FirstLayerPlaneMode::BeltAffine: {
+        // Compute the slicing-frame plane that maps to machine_Z = user_offset
+        // under the gcode axis remap (and optional back-transform).
+        MachineZAffine mz = compute_machine_z_affine(config);
+        double cmag = mz.gradient.norm();
+        if (cmag < EPSILON) {
+            // Degenerate: slicing point doesn't affect machine_Z.  Fall back.
+            set_axis_aligned(Vec3d::UnitZ(), user_offset);
+            m_active = false;
+            return;
+        }
+        // Plane equation: gradient · slicing = user_offset - constant
+        const double K = user_offset - mz.constant;
+        m_normal = mz.gradient / cmag;
+        m_offset = K / cmag;
+        m_active = true;
+        return;
+    }
+
+    case FirstLayerPlaneMode::Auto:
+        // Should have been resolved above.
+        m_active = false;
+        return;
+    }
+
+    m_active = false;
+}
+
+double FirstLayerPlane::distance_from_plane(const Vec3d &point_slicing_mm) const
+{
+    return m_normal.dot(point_slicing_mm) - m_offset;
+}
+
+bool FirstLayerPlane::is_first_layer(const Vec3d &point_slicing_mm,
+                                     double first_layer_height_mm) const
+{
+    if (!m_active)
+        return false;
+    return distance_from_plane(point_slicing_mm) < first_layer_height_mm;
+}
+
+int FirstLayerPlane::effective_layer_index(const Vec3d &point_slicing_mm) const
+{
+    if (!m_active)
+        return INT_MAX / 2;  // Effectively "way past first layer".
+    double d = distance_from_plane(point_slicing_mm);
+    if (d <= 0.0)
+        return 0;
+    return int(std::floor(d / m_thickness_mm));
+}
+
+int FirstLayerPlane::min_effective_index_for_xy_bbox(
+    const BoundingBoxf &xy_bbox_mm, double slicing_z_mm) const
+{
+    if (!m_active)
+        return INT_MAX / 2;
+    // For the rectangular bbox in (x, y) at fixed z, the smallest value of
+    // (n.x*x + n.y*y + n.z*z - offset) is achieved at one of the four
+    // corners, with the smaller component picked when the corresponding
+    // normal coefficient is positive.
+    const double x_for_min = (m_normal.x() >= 0.0)
+        ? xy_bbox_mm.min.x() : xy_bbox_mm.max.x();
+    const double y_for_min = (m_normal.y() >= 0.0)
+        ? xy_bbox_mm.min.y() : xy_bbox_mm.max.y();
+    const double dmin = m_normal.x() * x_for_min
+                      + m_normal.y() * y_for_min
+                      + m_normal.z() * slicing_z_mm
+                      - m_offset;
+    if (dmin <= 0.0)
+        return 0;
+    return int(std::floor(dmin / m_thickness_mm));
+}
+
+int FirstLayerPlane::min_effective_index_for_bbox3(
+    const BoundingBoxf3 &bbox_mm) const
+{
+    if (!m_active)
+        return INT_MAX / 2;
+    const double x_for_min = (m_normal.x() >= 0.0)
+        ? bbox_mm.min.x() : bbox_mm.max.x();
+    const double y_for_min = (m_normal.y() >= 0.0)
+        ? bbox_mm.min.y() : bbox_mm.max.y();
+    const double z_for_min = (m_normal.z() >= 0.0)
+        ? bbox_mm.min.z() : bbox_mm.max.z();
+    const double dmin = m_normal.x() * x_for_min
+                      + m_normal.y() * y_for_min
+                      + m_normal.z() * z_for_min
+                      - m_offset;
+    if (dmin <= 0.0)
+        return 0;
+    return int(std::floor(dmin / m_thickness_mm));
+}
+
+} // namespace Slic3r
@@ -0,0 +1,76 @@
+#ifndef slic3r_FirstLayerPlane_hpp_
+#define slic3r_FirstLayerPlane_hpp_
+
+#include "libslic3r.h"
+#include "Point.hpp"
+#include "BoundingBox.hpp"
+#include "PrintConfig.hpp"
+
+namespace Slic3r {
+
+// Decides which extrusions get "first layer" treatment (no fan, slow speed,
+// initial-layer accel/jerk, deferred temperature drop) by reference to a
+// configurable plane in slicing-frame coordinates rather than the slicing
+// layer index.
+//
+// On a normal flat-bed printer the plane is XY at slicing_Z = 0 and the
+// evaluator is INACTIVE — every call site short-circuits back to the legacy
+// `Layer::id() == 0` test.  On a belt printer with a Z-from-Y shear the
+// belt surface (machine_Z = 0) maps to a plane in slicing-frame coordinates
+// derived from the gcode axis remap, so layer-index-based detection no
+// longer matches the physical first printed surface.
+//
+// Plane representation: unit normal `n` (slicing frame) and offset along
+// the normal such that the plane equation is `n · p == offset`.  Signed
+// perpendicular distance is `d(p) = n · p - offset`.  Positive distance
+// means "away from the belt surface", negative means "below the plane".
+class FirstLayerPlane
+{
+public:
+    explicit FirstLayerPlane(const PrintConfig &config);
+
+    // Inactive when the legacy XY layer-index path should be used.  This
+    // covers all non-belt printers and any belt printer where the user
+    // explicitly picked XY mode.
+    bool                is_active() const     { return m_active; }
+    FirstLayerPlaneMode effective_mode() const{ return m_mode; }
+    double              band_thickness_mm() const { return m_thickness_mm; }
+    const Vec3d &       normal() const        { return m_normal; }
+    double              plane_offset() const  { return m_offset; }
+
+    // Signed perpendicular distance from a slicing-frame point to the plane.
+    double distance_from_plane(const Vec3d &point_slicing_mm) const;
+
+    // True if perpendicular distance < first_layer_height_mm.  When the
+    // evaluator is inactive this returns false (call sites should fall back
+    // to the legacy per-layer path before reaching this function).
+    bool is_first_layer(const Vec3d &point_slicing_mm,
+                        double first_layer_height_mm) const;
+
+    // floor((distance - 0) / band_thickness), clamped to [0, +inf).  Used
+    // for "first N layers" thresholds (fan, slow_down_layers).  Returns 0
+    // for points within the band.  Returns INT_MAX/2 when inactive.
+    int effective_layer_index(const Vec3d &point_slicing_mm) const;
+
+    // Min effective index over a 2D bbox at a fixed slicing_Z.  Used for
+    // layer-level decisions (e.g. temperature transition gate) where we
+    // don't want to walk every extrusion in the layer.  For axis-aligned
+    // planes this is exact; for tilted planes it's a tight lower bound
+    // (the plane projection of the bbox's extreme corner).
+    int min_effective_index_for_xy_bbox(const BoundingBoxf &xy_bbox_mm,
+                                        double              slicing_z_mm) const;
+
+    // Same as above but the bbox spans a Z range too.
+    int min_effective_index_for_bbox3(const BoundingBoxf3 &bbox_mm) const;
+
+private:
+    bool                m_active        = false;
+    FirstLayerPlaneMode m_mode          = FirstLayerPlaneMode::XY;
+    Vec3d               m_normal        = Vec3d::UnitZ();  // unit, slicing frame
+    double              m_offset        = 0.0;             // n·p == m_offset
+    double              m_thickness_mm  = 0.0;
+};
+
+} // namespace Slic3r
+
+#endif // slic3r_FirstLayerPlane_hpp_
@@ -1041,10 +1041,10 @@ void PlateData::parse_filament_info(GCodeProcessorResult *result)
            void _stop_object_xml_parser(const std::string& msg = std::string())
            {
                assert(! obj_parse_error);
-                assert(obj_parse_error_message.empty());
                assert(object_xml_parser != nullptr);
                obj_parse_error = true;
-                obj_parse_error_message = msg;
+                if (! msg.empty() || obj_parse_error_message.empty())   // a handler may have set the message already
+                    obj_parse_error_message = msg;
                XML_StopParser(object_xml_parser, false);
            }

@@ -3901,11 +3901,18 @@ void PlateData::parse_filament_info(GCodeProcessorResult *result)
    {
        // appends the vertex coordinates
        // missing values are set equal to ZERO
-        if (m_curr_object)
-            m_curr_object->geometry.vertices.emplace_back(
-                m_unit_factor * bbs_get_attribute_value_float(attributes, num_attributes, X_ATTR),
-                m_unit_factor * bbs_get_attribute_value_float(attributes, num_attributes, Y_ATTR),
-                m_unit_factor * bbs_get_attribute_value_float(attributes, num_attributes, Z_ATTR));
+        if (m_curr_object) {
+            const Vec3f v(m_unit_factor * bbs_get_attribute_value_float(attributes, num_attributes, X_ATTR),
+                          m_unit_factor * bbs_get_attribute_value_float(attributes, num_attributes, Y_ATTR),
+                          m_unit_factor * bbs_get_attribute_value_float(attributes, num_attributes, Z_ATTR));
+            // A non-finite coordinate ("nan", "inf") used to be accepted and crashed
+            // qhull in ModelVolume's convex hull while the file was still loading. Refuse the file.
+            if (! v.allFinite()) {
+                _stop_xml_parser("Invalid vertex coordinate: not a finite number");
+                return true;   // the parser is stopped; returning false would overwrite the message
+            }
+            m_curr_object->geometry.vertices.emplace_back(v);
+        }
        return true;
    }

@@ -5195,6 +5202,11 @@ void PlateData::parse_filament_info(GCodeProcessorResult *result)
                    }
                }

+                for (const Vec3f &v : sub_object->geometry.vertices)
+                    if (! v.allFinite()) {   // Qhull cannot take a NaN vertex
+                        add_error("invalid (non-finite) vertex in object " + std::to_string(sub_object->id));
+                        return false;
+                    }
                its.vertices.assign(sub_object->geometry.vertices.begin(), sub_object->geometry.vertices.end());

                // BBS
@@ -5708,11 +5720,18 @@ void PlateData::parse_filament_info(GCodeProcessorResult *result)
    {
        // appends the vertex coordinates
        // missing values are set equal to ZERO
-        if (current_object)
-            current_object->geometry.vertices.emplace_back(
-                object_unit_factor * bbs_get_attribute_value_float(attributes, num_attributes, X_ATTR),
-                object_unit_factor * bbs_get_attribute_value_float(attributes, num_attributes, Y_ATTR),
-                object_unit_factor * bbs_get_attribute_value_float(attributes, num_attributes, Z_ATTR));
+        if (current_object) {
+            const Vec3f v(object_unit_factor * bbs_get_attribute_value_float(attributes, num_attributes, X_ATTR),
+                          object_unit_factor * bbs_get_attribute_value_float(attributes, num_attributes, Y_ATTR),
+                          object_unit_factor * bbs_get_attribute_value_float(attributes, num_attributes, Z_ATTR));
+            // See _BBS_3MF_Importer::_handle_start_vertex: a non-finite coordinate
+            // crashed qhull while the file loaded. The dispatcher stops this parser on `false`.
+            if (! v.allFinite()) {
+                obj_parse_error_message = "Invalid vertex coordinate: not a finite number";
+                return false;
+            }
+            current_object->geometry.vertices.emplace_back(v);
+        }
        return true;
    }

@@ -7,6 +7,8 @@
 #include "Print.hpp"
 #include "libslic3r.h"
 #include "GCodeWriter.hpp"
+#include "GCode/BeltKinematics.hpp"
+#include "FirstLayerPlane.hpp"
 #include "Layer.hpp"
 #include "Point.hpp"
 #include "PlaceholderParser.hpp"
@@ -40,13 +42,16 @@
 #include <memory>
 #include <map>
 #include <unordered_map>
+#include <optional>
 #include <set>
 #include <string>
 #include <cfloat>
 #include <vector>
 #include <utility>
+#include <cmath>
 #include "BoundingBox.hpp"
 #include "Polyline.hpp"
+#include "BeltBrim.hpp"

 namespace Slic3r { class ExtrusionEntityCollection; }

@@ -249,8 +254,9 @@ public:
        m_toolchange_count(0),
        m_nominal_z(0.)
        {}
-    ~GCode() = default;
+    virtual ~GCode() = default;

+public:
    // throws std::runtime_exception on error,
    // throws CanceledException through print->throw_if_canceled().
    void            do_export(Print* print, const char* path, GCodeProcessorResult* result = nullptr, ThumbnailsGeneratorCallback thumbnail_cb = nullptr);
@@ -342,6 +348,13 @@ public:
        const Layer* 		object_layer;
        const SupportLayer* support_layer;
        const PrintObject*  original_object; //BBS: used for shared object logic
+        // Belt printers only: an apron band that prints BELOW the object's first
+        // layer, so it has no object or support layer of its own.  Deliberately
+        // not a Layer, so it cannot leak Layer::id() semantics into initial-layer
+        // temperature, spiral vase, cooling or interpolation logic.  When this is
+        // the only thing set, layer() is null and process_layer() takes its
+        // dedicated brim-only branch.
+        const BeltBrimBand* belt_brim_band { nullptr };
        const Layer* 		layer()   const
        {
            if (object_layer != nullptr)
@@ -371,11 +384,25 @@ public:
                count++;
            }

+            // A brim-only apron band contributes no object/support layer, and
+            // averaging zero terms would yield NaN.  Never folded into the
+            // average, so the non-belt result is bit-identical.
+            if (count == 0 && belt_brim_band != nullptr)
+                return belt_brim_band->print_z;
+
            return sum_z / count;
        }
    };

-private:
+    // Public accessor for the first-layer plane evaluator.  Used by
+    // CoolingBuffer (which is constructed with a GCode reference and needs
+    // to read the plane for per-segment fan re-evaluation).  All other
+    // first-layer-plane access points (on_first_layer overload, effective
+    // index helper) are in the protected section since they're called from
+    // GCode internals only.
+    const FirstLayerPlane *first_layer_plane() const { return m_first_layer_plane.get(); }
+
+protected:
    class GCodeOutputStream {
    public:
        GCodeOutputStream(FILE *f, GCodeProcessor &processor) : f(f), m_processor(processor) {}
@@ -403,9 +430,21 @@ private:
        FILE *f = nullptr;
        GCodeProcessor &m_processor;
    };
+
+    // Virtual hooks for belt printer subclass (BeltGCode).
+    // No-ops in base GCode; overridden in BeltGCode.
+    virtual void init_belt_writer(Print &print) {}
+    virtual void write_belt_header(GCodeOutputStream &file, const Print &print) {}
+    virtual void on_set_origin(const PrintObject *obj, const Point &inst_shift) {}
+    // Arc fitting is suppressed whenever the writer's machine mapping cannot
+    // represent a G2/G3 arc. Belt printers get this through BeltKinematics
+    // rather than through an override of their own.
+    virtual bool should_disable_arc_fitting() const
+        { return ! m_writer.kinematics().supports_arc_moves(); }
+
    void            _do_export(Print &print, GCodeOutputStream &file, ThumbnailsGeneratorCallback thumbnail_cb);

-    static std::vector<LayerToPrint>        		                   collect_layers_to_print(const PrintObject &object);
+    static std::vector<LayerToPrint>        		                   collect_layers_to_print(const PrintObject &object, bool skip_empty_first_layer = false);
    static std::vector<std::pair<coordf_t, std::vector<LayerToPrint>>> collect_layers_to_print(const Print &print);

    std::string generate_skirt(const Print &print,
@@ -425,7 +464,29 @@ private:
    std::string generate_object_brim(const Print &print,
        const PrintObject &object,
        size_t instance_id,
-        bool first_layer);
+        bool first_layer,
+        const Layer *object_layer);
+
+    // Belt printers: emit one brim-only apron layer.  These print below the
+    // object's first layer, so there is no object or support layer for the normal
+    // process_layer() machinery to work from.  Kept to the minimum a layer needs -
+    // tool, Z move, extrusions - so that nothing here can perturb the
+    // Layer::id()-based logic the ordinary path relies on.
+    LayerResult process_belt_brim_layer(
+        const Print                     &print,
+        const std::vector<LayerToPrint> &layers,
+        const LayerTools                &layer_tools,
+        const bool                       last_layer,
+        const size_t                     single_object_instance_idx);
+
+    // Emit the apron bands carried by these layers whose brim filament is extruder_id
+    // (0-based).  Called from both the brim-only branch and the ordinary path, since a
+    // band's print_z can coincide with another object's layer on a multi-object belt.
+    std::string emit_belt_brim_bands(
+        const Print                     &print,
+        const std::vector<LayerToPrint> &layers,
+        const size_t                     single_object_instance_idx,
+        const unsigned int               extruder_id);

    LayerResult process_layer(
        const Print                     &print,
@@ -629,9 +690,21 @@ private:
    };

    // Cache the per-filament island tour to avoid recomputing while the layer's island layout is
-    // unchanged. Key: filament_id. Value: {nodes the tour was computed from, resulting visits}.
-    std::map<unsigned int, std::pair<std::vector<IslandOrderNode>, std::vector<InstanceVisit>>>
-                                        m_ordering_cache;
+    // unchanged. Key: filament_id. Value: the nodes the tour was computed from, the per-instance
+    // island layout (count and whether the trailing catch-all island has anything to print), and
+    // the resulting visits.
+    // The layout is part of the key. Nodes only cover the chainable islands, so two
+    // layers with the same centroids but a different number of islands (thin walls, negative
+    // volumes come and go) matched the cache and the visit's catch-all index -- islands.size() - 1
+    // of the OLD layer -- ran past the new layer's islands (found by fuzzing: segfault in
+    // extrude_perimeters on multi-part objects).
+    struct IslandOrderCacheEntry
+    {
+        std::vector<IslandOrderNode>         nodes;
+        std::vector<std::pair<size_t, bool>> layout;
+        std::vector<InstanceVisit>           visits;
+    };
+    std::map<unsigned int, IslandOrderCacheEntry> m_ordering_cache;

    ExtrusionQualityEstimator m_extrusion_quality_estimator;

@@ -768,6 +841,12 @@ private:

    std::unique_ptr<CoolingBuffer>      m_cooling_buffer;
    std::unique_ptr<SpiralVase>         m_spiral_vase;
+    // First-layer plane evaluator.  Constructed once per print from the
+    // PrintConfig.  is_active() == false on non-belt printers and on belt
+    // printers without a Z-axis shear; in that case all per-path plane
+    // checks short-circuit to the legacy Layer::id() == 0 path.
+    std::unique_ptr<FirstLayerPlane>    m_first_layer_plane;
+    // Plate origin, kept so a writer replaced during export can be given it again.

    std::unique_ptr<PressureEqualizer>  m_pressure_equalizer;
    
@@ -823,6 +902,25 @@ private:
    mutable ConfigIndexCache m_filament_index_cache;
    mutable ConfigIndexCache m_nozzle_index_cache;

+    // Belt brim apron layers only.  They have no Layer, so the print_z that
+    // _extrude() needs for the first-layer-plane probe is published here instead.
+    // Scoped by BeltBrimZGuard in process_belt_brim_layer(), never left set.
+    std::optional<coordf_t> m_belt_brim_z;
+    // Belt brim only.  Brim and coincident apron bands are emitted before m_layer
+    // is switched to their object, so belt_height_above_floor() would otherwise
+    // read the previously visited object's belt description -- making a brim's
+    // classification depend on plate visiting order.  Those paths publish the
+    // owner here for the duration of the emission.  Never left set.
+    const PrintObject *m_belt_floor_object{nullptr};
+    struct BeltFloorObjectGuard {
+        const PrintObject *&slot;
+        BeltFloorObjectGuard(const PrintObject *&s, const PrintObject *o) : slot(s) { slot = o; }
+        ~BeltFloorObjectGuard() { slot = nullptr; }
+    };
+
+    // The last extrusion segment was inside the belt's first-layer fan band (see _extrude()).
+    bool m_belt_in_band{false};
+
    std::set<unsigned int>                  m_initial_layer_extruders;
    std::vector<std::vector<unsigned int>>  m_sorted_layer_filaments;
    // BBS
@@ -840,6 +938,64 @@ private:
    // On the first printing layer. This flag triggers first layer speeds.
    //BBS
    bool    on_first_layer() const { return m_layer != nullptr && m_layer->id() == 0 && abs(m_layer->bottom_z()) < EPSILON; }
+    // Per-point first-layer test.  When the FirstLayerPlane evaluator is
+    // active, the result depends on the supplied slicing-frame point;
+    // otherwise we delegate to the legacy per-layer test.  This is the
+    // entry point used by per-path call sites in _extrude.
+    bool on_first_layer(const Vec3d &point_slicing_mm) const {
+        // Belt printers: measure height above the belt surface itself, in the
+        // slicing frame. See belt_height_above_floor() for why this does not go
+        // through FirstLayerPlane.
+        double h;
+        if (this->belt_height_above_floor(point_slicing_mm, h))
+            return h <= m_config.initial_layer_print_height.value + EPSILON;
+        if (m_first_layer_plane && m_first_layer_plane->is_active())
+            return m_first_layer_plane->is_first_layer(
+                point_slicing_mm, m_config.initial_layer_print_height.value);
+        return on_first_layer();
+    }
+    // "Effective layer index" used to drive layer-count thresholds like
+    // slow_down_layers.  When the evaluator is active this returns the
+    // perpendicular distance to the plane in band_thickness_mm units;
+    // otherwise it returns the legacy slicing layer index.
+    int effective_layer_index_for_point(const Vec3d &point_slicing_mm) const {
+        double h;
+        if (this->belt_height_above_floor(point_slicing_mm, h)) {
+            const double lh = this->first_layer_band_mm();
+            return h <= 0. ? 0 : int(std::floor(h / lh));
+        }
+        if (m_first_layer_plane && m_first_layer_plane->is_active())
+            return m_first_layer_plane->effective_layer_index(point_slicing_mm);
+        return on_first_layer() ? 0 : layer_id();
+    }
+
+    // Band thickness for the *effective layer index* only.  FirstLayerPlane keeps
+    // two separate thresholds and so must this path: is_first_layer() tests
+    // against initial_layer_print_height, while effective_layer_index() counts
+    // bands of first_layer_plane_thickness.  Conflating them would apply
+    // first-layer treatment through a whole 1mm band on a 0.2mm first layer.
+    double first_layer_band_mm() const {
+        double band = m_config.first_layer_plane_thickness.value;
+        if (band <= 0.) band = m_config.initial_layer_print_height.value;
+        return band > 0. ? band : 0.2;
+    }
+
+    // Height of a slicing-frame point above the belt surface, or false when this
+    // is not a belt print.
+    //
+    // The belt surface is known exactly in the slicing frame from the slicing
+    // parameters (belt_floor_shear_factor / _from_axis / _z_shift) -- the same
+    // description the support generator uses. FirstLayerPlane instead derives its
+    // plane by composing gcode_remap_* with the g-code back-transform, so its
+    // answer changes with the machine's *output* axis convention: on a printer
+    // with a non-identity remap it reported ~86mm of clearance for geometry
+    // sitting directly on the belt, and no extrusion was ever classified as
+    // first-layer. Measuring against the belt itself is independent of every
+    // remap and back-transform.
+    bool belt_height_above_floor(const Vec3d &point_slicing_mm, double &height_mm) const;
+    // 1 / 0 / -1: the object layer is entirely past the first-layer band above the
+    // belt / reaches into it / the belt surface is not known for it.
+    int  belt_layer_past_first_layer_band(const Layer *object_layer) const;
    int layer_id() const {
        if (m_layer == nullptr)
            return -1;
@@ -0,0 +1,42 @@
+#include "BeltBackTransform.hpp"
+#include "../BeltTransform.hpp"
+#include "../Point.hpp"
+#include "../PrintConfig.hpp"
+
+namespace Slic3r {
+
+bool BeltBackTransform::init_from_config(const PrintConfig &config)
+{
+    m_active  = false;
+    m_inverse = Transform3d::Identity();
+
+    if (!config.belt_printer.value || !config.gcode_back_transform.value)
+        return false;
+
+    // Require at least one active transform to proceed.
+    bool has_global_rotation = config.belt_slice_rotation_global.value
+                            && config.belt_slice_rotation.value != BeltRotationAxis::None;
+    bool has_preslice_global = config.belt_preslice_global.value
+                            || config.preslice_remap_global.value;
+    if (!has_global_rotation && !has_preslice_global
+        && !BeltTransformPipeline::has_preslice_remap(config))
+        return false;
+
+    // Build the forward pipeline (rotation * pre_remap) and store its inverse.
+    Transform3d forward = BeltTransformPipeline::build_forward_transform(config);
+    if (forward.isApprox(Transform3d::Identity()))
+        return false;
+
+    m_inverse = forward.inverse();
+    m_active  = true;
+    return true;
+}
+
+Vec3d BeltBackTransform::apply(const Vec3d &pos) const
+{
+    if (!m_active)
+        return pos;
+    return m_inverse * pos;
+}
+
+} // namespace Slic3r
@@ -0,0 +1,45 @@
+#ifndef slic3r_BeltBackTransform_hpp_
+#define slic3r_BeltBackTransform_hpp_
+
+#include "../libslic3r.h"
+#include "../Point.hpp"
+#include "../PrintConfig.hpp"
+
+namespace Slic3r {
+
+// Reverses the pre-slice remap + shear + scale transforms that
+// PrintObjectSlice.cpp applies to belt printer geometry, converting G-code
+// coordinates from the sliced (remapped/sheared/scaled) frame back to the
+// machine's real coordinate space.
+//
+// Initialized once from PrintConfig, then applied per-point in
+// BeltKinematics::to_machine() before axis remapping.
+//
+// Active when gcode_back_transform is true AND at least one of:
+//   - a shear axis has global mode enabled, or
+//   - a pre-slice axis remap is non-identity.
+class BeltBackTransform
+{
+public:
+    BeltBackTransform() = default;
+
+    // Initialize from belt printer config.  Rebuilds the same pre-slice remap,
+    // shear, and scale matrices as PrintObjectSlice.cpp and precomputes the
+    // affine inverse.  Returns true if a non-identity back-transform was computed.
+    bool init_from_config(const PrintConfig &config);
+
+    // Apply the inverse transform to a point.  Returns pos unchanged if
+    // no back-transform is active.
+    Vec3d apply(const Vec3d &pos) const;
+
+    // True if a non-identity back-transform is active.
+    bool is_active() const { return m_active; }
+
+private:
+    bool       m_active  = false;
+    Transform3d m_inverse = Transform3d::Identity();
+};
+
+} // namespace Slic3r
+
+#endif // slic3r_BeltBackTransform_hpp_
@@ -0,0 +1,42 @@
+#include "BeltKinematics.hpp"
+#include "../BeltTransform.hpp"
+#include "../PrintConfig.hpp"
+#include "../GCodeWriter.hpp"
+#include "../Point.hpp"
+#include <memory>
+
+namespace Slic3r {
+
+BeltKinematics::BeltKinematics(const PrintConfig &config, bool world_coordinates)
+    : m_world_coordinates(world_coordinates)
+{
+    m_back_active = m_back_transform.init_from_config(config);
+    m_machine_frame.init_from_config(config);
+    if (m_back_active)
+        // BeltBackTransform stores the inverse of this; keep the forward so
+        // to_logical() can reverse the whole chain.
+        m_back_forward = BeltTransformPipeline::build_forward_transform(config);
+}
+
+Vec3d BeltKinematics::to_machine(const Vec3d &p) const
+{
+    const Vec3d after_back  = m_world_coordinates ? p : m_back_transform.apply(p);
+    const Vec3d after_remap = this->apply_axis_remap(after_back);
+    return m_machine_frame.apply(after_remap);
+}
+
+Vec3d BeltKinematics::to_logical(const Vec3d &machine) const
+{
+    const Vec3d before_frame = m_machine_frame.apply_inverse(machine);
+    const Vec3d before_remap = this->apply_axis_remap_inverse(before_frame);
+    if (m_world_coordinates || ! m_back_active)
+        return before_remap;
+    return m_back_forward * before_remap;
+}
+
+void install_belt_kinematics(GCodeWriter &writer, const PrintConfig &config, bool world_coordinates)
+{
+    writer.set_kinematics(std::make_unique<BeltKinematics>(config, world_coordinates));
+}
+
+} // namespace Slic3r
@@ -0,0 +1,70 @@
+#ifndef slic3r_BeltKinematics_hpp_
+#define slic3r_BeltKinematics_hpp_
+
+#include "MachineKinematics.hpp"
+#include "BeltBackTransform.hpp"
+#include "MachineFrameTransform.hpp"
+#include "../Point.hpp"
+
+namespace Slic3r {
+
+class PrintConfig;
+class GCodeWriter;
+
+// Belt-printer machine frame.
+//
+// Forward order, as applied per emitted point:
+//     machine = MachineFrameTransform( axis_remap( BeltBackTransform( logical ) ) )
+//
+// i.e. the slicer->world back-transform runs FIRST and the machine-frame
+// shear/scale LAST, so the latter acts as a global linear transform on the
+// already-placed coordinates.
+//
+// world_coordinates mode (the PA line / PA pattern calibration generators)
+// treats the incoming point as already relative to the belt surface -- X across,
+// Y along the belt, Z above it -- and therefore skips the back-transform while
+// keeping the remap and the machine frame. It is a different coordinate map, not
+// a writer mode, which is why it is fixed at construction.
+class BeltKinematics : public CartesianKinematics
+{
+public:
+    explicit BeltKinematics(const PrintConfig &config, bool world_coordinates = false);
+
+    Vec3d to_machine(const Vec3d &p) const override;
+    Vec3d to_logical(const Vec3d &machine) const override;
+    // Machine -> build-volume frame. Only the machine-frame shear/scale is undone,
+    // matching what GCodeProcessor's bounds validation wants. This is deliberately
+    // NOT to_logical().
+    Vec3d to_build_volume(const Vec3d &machine) const override
+        { return m_machine_frame.apply_inverse(machine); }
+
+    // A belt writer has always emitted full XYZ on every move, whether or not any
+    // individual stage reports itself active. Making this conditional would change
+    // emitted G-code for an identity-transform belt configuration.
+    bool must_emit_all_axes() const override { return true; }
+    bool suppress_lift_at_unknown_position() const override { return true; }
+    // The machine frame shears and scales, so a circle is an ellipse in machine
+    // coordinates and G2/G3 cannot describe it.
+    bool supports_arc_moves() const override { return false; }
+
+    bool world_coordinates() const { return m_world_coordinates; }
+
+private:
+    BeltBackTransform     m_back_transform;
+    MachineFrameTransform m_machine_frame;
+    // Forward of what m_back_transform inverts, kept so to_logical() can undo it.
+    Transform3d           m_back_forward { Transform3d::Identity() };
+    bool                  m_back_active { false };
+    bool                  m_world_coordinates { false };
+};
+
+// Install a belt machine frame on any GCodeWriter. Any axis remap and build
+// volume already configured on the writer are carried over, so this may be
+// called before or after those setters. Re-calling it with a different
+// world_coordinates value swaps the map (used around the PA line generator).
+void install_belt_kinematics(GCodeWriter &writer, const PrintConfig &config,
+                             bool world_coordinates = false);
+
+} // namespace Slic3r
+
+#endif // slic3r_BeltKinematics_hpp_
@@ -18,6 +18,7 @@
 #include <iostream>
 #include <float.h>
 #include <string>
+#include <string_view>
 #include <system_error>
 #include <unordered_map>
 #include <vector>
@@ -46,10 +47,12 @@ CoolingBuffer::CoolingBuffer(GCode &gcodegen) : m_config(gcodegen.config()), m_g
        m_num_extruders = std::max(ex.id() + 1, m_num_extruders);
        m_extruder_ids.emplace_back(ex.id());
    }
+
 }

 void CoolingBuffer::reset(const Vec3d &position)
 {
+    m_belt_band_active = false;
    // BBS: add I and J axis to store center of arc
    m_current_pos.assign(7, 0.f);
    m_current_pos[0] = float(position.x());
@@ -89,6 +92,9 @@ struct CoolingLine
        // ORCA: Add support for ironing fan speed control
        TYPE_IRONING_FAN_START         = 1 << 19,
        TYPE_IRONING_FAN_END           = 1 << 20,
+        // Belt printers: extrusions within the first-layer band above the belt.
+        TYPE_BELT_BAND_START           = 1 << 21,
+        TYPE_BELT_BAND_END             = 1 << 22,
    };

    CoolingLine(unsigned int type, size_t  line_start, size_t  line_end) :
@@ -549,6 +555,10 @@ std::vector<PerExtruderAdjustments> CoolingBuffer::parse_layer_gcode(const std::
            line.type = CoolingLine::TYPE_IRONING_FAN_START;
        } else if (boost::starts_with(sline, ";_IRONING_FAN_END")) { // ORCA: Add support for ironing fan speed control
            line.type = CoolingLine::TYPE_IRONING_FAN_END;
+        } else if (boost::starts_with(sline, ";_BELT_BAND_START")) {
+            line.type = CoolingLine::TYPE_BELT_BAND_START;
+        } else if (boost::starts_with(sline, ";_BELT_BAND_END")) {
+            line.type = CoolingLine::TYPE_BELT_BAND_END;
        } else if (boost::starts_with(sline, "G4 ")) {
            // Parse the wait time.
            line.type = CoolingLine::TYPE_G4;
@@ -891,7 +901,9 @@ std::string CoolingBuffer::apply_layer_cooldown(
                                                               {CoolingLine::TYPE_SUPPORT_INTERFACE_FAN_START, false},
                                                               {CoolingLine::TYPE_IRONING_FAN_START, false}, // ORCA: Add support for ironing fan speed control
                                                               {CoolingLine::TYPE_FORCE_RESUME_FAN, false}};
-    bool need_set_fan = false;
+    // Belt printers: a band still open from the previous layer has to take the fan back from
+    // the layer-level speed issued just above.
+    bool need_set_fan = m_belt_band_active;

    for (const CoolingLine *line : lines) {
        const char *line_start  = gcode.c_str() + line->line_start;
@@ -905,6 +917,8 @@ std::string CoolingBuffer::apply_layer_cooldown(
                if (new_extruder != m_current_extruder) {
                    m_current_extruder = new_extruder;
                    change_extruder_set_fan(true);
+                    if (m_belt_band_active)
+                        need_set_fan = true;
                }
            }
            new_gcode.append(line_start, line_end - line_start);
@@ -957,6 +971,13 @@ std::string CoolingBuffer::apply_layer_cooldown(
            if (m_additional_fan_speed != -1 && m_config.auxiliary_fan.value)
                new_gcode += GCodeWriter::set_additional_fan(m_additional_fan_speed);
        }
+        else if (line->type & CoolingLine::TYPE_BELT_BAND_START) {
+            m_belt_band_active = true;
+            need_set_fan       = true;
+        } else if (line->type & CoolingLine::TYPE_BELT_BAND_END) {
+            m_belt_band_active = false;
+            need_set_fan       = true;
+        }
        else if (line->type & CoolingLine::TYPE_EXTRUDE_END) {
            // Just remove this comment.
        } else if (line->type & (CoolingLine::TYPE_ADJUSTABLE | CoolingLine::TYPE_EXTERNAL_PERIMETER | CoolingLine::TYPE_WIPE | CoolingLine::TYPE_HAS_F)) {
@@ -1049,7 +1070,15 @@ std::string CoolingBuffer::apply_layer_cooldown(
                    m_current_fan_speed = speed;
                }
            };
-            if (fan_speed_change_requests[CoolingLine::TYPE_OVERHANG_FAN_START]){
+            if (m_belt_band_active) {
+                // Belt printers: a tilted layer runs from the belt to the top of the part, so
+                // "the first layers" are a band along the belt rather than the first slicing
+                // layers. Extrusions GCode::_extrude() marks as inside that band print with the
+                // fan off, whatever overhang, bridge or resume request is pending, as the first
+                // layers of a flat bed do. Leaving the band falls through to the branches below.
+                set_fan(0);
+                fan_speed_change_requests[CoolingLine::TYPE_FORCE_RESUME_FAN] = false;
+            } else if (fan_speed_change_requests[CoolingLine::TYPE_OVERHANG_FAN_START]){
                set_fan(overhang_fan_speed);
            } else if (fan_speed_change_requests[CoolingLine::TYPE_INTERNAL_BRIDGE_FAN_START]){ // ORCA: Add support for separate internal bridge fan speed control
                set_fan(internal_bridge_fan_speed);
@@ -21,7 +21,7 @@ struct PerExtruderAdjustments;
 //
 // The simple it sounds, the actual implementation is significantly more complex.
 // Namely, for a multi-extruder print, each material may require a different cooling logic.
-// For example, some materials may not like to print too slowly, while with some materials 
+// For example, some materials may not like to print too slowly, while with some materials
 // we may slow down significantly.
 //
 class CoolingBuffer {
@@ -63,6 +63,9 @@ private:
    unsigned int                m_current_nozzle;
    //BBS: current fan speed
    int                         m_current_fan_speed;
+    // Belt printers: the extrusion being processed lies in the first-layer band above the
+    // belt (between a ";_BELT_BAND_START" and a ";_BELT_BAND_END"). Kept across layers.
+    bool                        m_belt_band_active = false;
 };

 }
@@ -751,50 +751,6 @@ template<typename T>
    }
 }

-namespace {
-// Writes G-code to a file in blocks and records in lines_ends the file offset after every '\n'
-class GCodeFileWriter
-{
-public:
-    GCodeFileWriter(FilePtr& out, const std::string& out_path, std::vector<size_t>& lines_ends, const char* error_message)
-        : m_out(out), m_out_path(out_path), m_lines_ends(lines_ends), m_error_message(error_message)
-    {}
-    ~GCodeFileWriter() { assert(m_buffer.empty() || std::uncaught_exceptions() > 0); }
-
-    void append(std::string_view text)
-    {
-        const size_t text_pos = m_file_pos + m_buffer.size();
-        for (size_t i = text.find('\n'); i != std::string_view::npos; i = text.find('\n', i + 1))
-            m_lines_ends.emplace_back(text_pos + i + 1);
-        m_buffer += text;
-        if (m_buffer.size() >= GCodeProcessor::Output_Block_Size)
-            flush();
-    }
-
-    void flush()
-    {
-        if (m_buffer.empty())
-            return;
-        fwrite(m_buffer.data(), 1, m_buffer.size(), m_out.f);
-        if (ferror(m_out.f)) {
-            m_out.close();
-            boost::nowide::remove(m_out_path.c_str());
-            throw Slic3r::RuntimeError(m_error_message);
-        }
-        m_file_pos += m_buffer.size();
-        m_buffer.clear();
-    }
-
-private:
-    FilePtr&             m_out;
-    const std::string&   m_out_path;
-    std::vector<size_t>& m_lines_ends;
-    const char*          m_error_message;
-    std::string          m_buffer;
-    size_t               m_file_pos{0};
-};
-} // namespace
-
 // Helper class to modify and export gcode to file
 class ExportLines
 {
@@ -809,6 +765,16 @@ public:
    enum class EWriteType { BySize, ByTime };

 private:
+    static void update_lines_ends_and_out_file_pos(const std::string& out_string, std::vector<size_t>& lines_ends, size_t* out_file_pos)
+    {
+        for (size_t i = 0; i < out_string.size(); ++i) {
+            if (out_string[i] == '\n')
+                lines_ends.emplace_back((out_file_pos != nullptr) ? *out_file_pos + i + 1 : i + 1);
+        }
+        if (out_file_pos != nullptr)
+            *out_file_pos += out_string.size();
+    }
+
    struct LineData
    {
        std::string                                                                        line;
@@ -848,14 +814,12 @@ private:
    EWriteType m_write_type{EWriteType::BySize};
    // Time machines containing g1 times cache
    const std::array<GCodeProcessor::TimeMachine, static_cast<size_t>(PrintEstimatedStatistics::ETimeMode::Count)>& m_machines;
-    // Output file writer
-    GCodeFileWriter& m_writer;
    // Current time
    std::array<float, static_cast<size_t>(PrintEstimatedStatistics::ETimeMode::Count)> m_times{0.0f, 0.0f};
-    // Current size of the cache in bytes
+    // Current size in bytes
    size_t m_size{0};

-    // gcode lines cache, used only when writing by time
+    // gcode lines cache
    std::deque<LineData> m_lines;
    size_t               m_added_lines_counter{0};
    // map of gcode line ids from original to final
@@ -863,16 +827,16 @@ private:
    std::vector<std::pair<size_t, size_t>> m_gcode_lines_map;

    size_t m_times_cache_id{0};
+    size_t m_out_file_pos{0};

 public:
-    ExportLines(EWriteType type, const std::array<GCodeProcessor::TimeMachine, static_cast<size_t>(PrintEstimatedStatistics::ETimeMode::Count)>& machines, GCodeFileWriter& writer)
+    ExportLines(EWriteType type, const std::array<GCodeProcessor::TimeMachine, static_cast<size_t>(PrintEstimatedStatistics::ETimeMode::Count)>& machines)
 #ifndef NDEBUG
        : m_statistics(*this)
        , m_write_type(type)
-        , m_machines(machines)
-        , m_writer(writer){}
+        , m_machines(machines){}
 #else
-        : m_write_type(type), m_machines(machines), m_writer(writer)
+        : m_write_type(type), m_machines(machines)
    {}
 #endif // NDEBUG

@@ -926,14 +890,11 @@ public:
        if (line.empty())
            return;

-        if (m_write_type == EWriteType::ByTime) {
-            m_lines.push_back({line, m_times});
+        m_lines.push_back({line, m_times});
 #ifndef NDEBUG
-            m_statistics.add_line(line.length());
+        m_statistics.add_line(line.length());
 #endif // NDEBUG
-            m_size += line.length();
-        } else
-            m_writer.append(line);
+        m_size += line.length();
        ++m_added_lines_counter;
        if (!ignore_from_move) {
            assert(!m_gcode_lines_map.empty());
@@ -999,35 +960,65 @@ public:
        }
    }

-    // when writing by time, pass the cached lines older than m_times[Normal] - backtrace_time to the writer
-    void write(float backtrace_time)
+    // write to file:
+    // m_write_type == EWriteType::ByTime - all lines older than m_time - backtrace_time
+    // m_write_type == EWriteType::BySize - all lines if current size is greater than 65535 bytes
+    void write(FilePtr& out, float backtrace_time, GCodeProcessorResult& result, const std::string& out_path)
    {
-        if (m_write_type != EWriteType::ByTime)
+        if (m_lines.empty())
            return;

-        while (!m_lines.empty() && m_lines.front().times[Normal] < m_times[Normal] - backtrace_time) {
-            const LineData& data = m_lines.front();
-            m_writer.append(data.line);
-            m_size -= data.line.length();
-            m_lines.pop_front();
+        // collect lines to write into a single string
+        std::string out_string;
+        if (!m_lines.empty()) {
+            if (m_write_type == EWriteType::ByTime) {
+                while (m_lines.front().times[Normal] < m_times[Normal] - backtrace_time) {
+                    const LineData& data = m_lines.front();
+                    out_string += data.line;
+                    m_size -= data.line.length();
+                    m_lines.pop_front();
 #ifndef NDEBUG
-            m_statistics.remove_line();
+                    m_statistics.remove_line();
 #endif // NDEBUG
+                }
+            } else {
+                if (m_size > 65535) {
+                    while (!m_lines.empty()) {
+                        out_string += m_lines.front().line;
+                        m_lines.pop_front();
+                    }
+                    m_size = 0;
+#ifndef NDEBUG
+                    m_statistics.remove_all_lines();
+#endif // NDEBUG
+                }
+            }
+        }
+
+        {
+            write_to_file(out, out_string, result, out_path);
+            update_lines_ends_and_out_file_pos(out_string, result.lines_ends, &m_out_file_pos);
        }
    }

-    // flush the current content of the cache and the writer to file
-    void flush()
+    // flush the current content of the cache to file
+    void flush(FilePtr& out, GCodeProcessorResult& result, const std::string& out_path)
    {
+        // collect lines to flush into a single string
+        std::string out_string;
        while (!m_lines.empty()) {
-            m_writer.append(m_lines.front().line);
+            out_string += m_lines.front().line;
            m_lines.pop_front();
        }
        m_size = 0;
 #ifndef NDEBUG
        m_statistics.remove_all_lines();
 #endif // NDEBUG
-        m_writer.flush();
+
+        {
+            write_to_file(out, out_string, result, out_path);
+            update_lines_ends_and_out_file_pos(out_string, result.lines_ends, &m_out_file_pos);
+        }
    }

    void synchronize_moves(GCodeProcessorResult& result) const
@@ -1060,7 +1051,20 @@ public:

    size_t get_size() const { return m_size; }

-    void reserve(size_t lines_count) { m_gcode_lines_map.reserve(lines_count); }
+private:
+    void write_to_file(FilePtr& out, const std::string& out_string, GCodeProcessorResult& result, const std::string& out_path)
+    {
+        if (!out_string.empty()) {
+            if (true) {
+                fwrite((const void*) out_string.c_str(), 1, out_string.length(), out.f);
+                if (ferror(out.f)) {
+                    out.close();
+                    boost::nowide::remove(out_path.c_str());
+                    throw Slic3r::RuntimeError("GCode processor post process export failed.\nIs the disk full?");
+                }
+            }
+        }
+    }
 };

 void GCodeProcessor::run_post_process()
@@ -1156,13 +1160,8 @@ void GCodeProcessor::run_post_process()
        last_exported_stop[i] = time_in_minutes(m_time_processor.machines[i].time);
    }

-    m_result.lines_ends.clear();
-    // m_result.lines_ends.emplace_back(std::vector<size_t>());
-    GCodeFileWriter writer(out, out_path, m_result.lines_ends, "GCode processor post process export failed.\nIs the disk full?");
    ExportLines export_line(m_result.backtrace_enabled ? ExportLines::EWriteType::ByTime : ExportLines::EWriteType::BySize,
-        m_time_processor.machines, writer);
-    // The line map holds an entry for each line of the file, and the first pass counted them
-    export_line.reserve(m_line_id);
+        m_time_processor.machines);

    // replace placeholder lines with the proper final value
    // gcode_line is in/out parameter, to reduce expensive memory allocation
@@ -1536,6 +1535,9 @@ void GCodeProcessor::run_post_process()
        }
    };

+    m_result.lines_ends.clear();
+    // m_result.lines_ends.emplace_back(std::vector<size_t>());
+
    // Orca: freshly collect SKIPPABLE ranges each post-process pass. The ranges are stored on the
    // member (rather than a local) so the injection pass can consume them, hence the clear here to
    // avoid stale ranges on re-invocation.
@@ -1800,7 +1802,7 @@ void GCodeProcessor::run_post_process()

                    if (!gcode_line.empty())
                        export_line.append_line(gcode_line);
-                    export_line.write(1.1f * max_backtrace_time);
+                    export_line.write(out, 1.1f * max_backtrace_time, m_result, out_path);
                    gcode_line.clear();
                }
            }
@@ -1842,7 +1844,7 @@ void GCodeProcessor::run_post_process()
        }
    }

-    export_line.flush();
+    export_line.flush(out, m_result, out_path);

    out.close();
    in.close();
@@ -1990,13 +1992,31 @@ void GCodeProcessor::run_second_pass_injection()
    // The rewrite may shift byte positions (once the injector inserts lines), so rebuild lines_ends from scratch.
    // With an empty map the scanned '\n' offsets reproduce the current lines_ends exactly.
    m_result.lines_ends.clear();
-    GCodeFileWriter writer(out, out_path, m_result.lines_ends, "GCode processor pre-heat injection pass failed.\nIs the disk full?\n");
+    size_t out_file_pos = 0;
+
+    auto write_out = [&out, &out_path, this, &out_file_pos](std::string& str) {
+        if (str.empty())
+            return;
+        fwrite((const void*) str.c_str(), 1, str.length(), out.f);
+        if (ferror(out.f)) {
+            out.close();
+            boost::nowide::remove(out_path.c_str());
+            throw Slic3r::RuntimeError(std::string("GCode processor pre-heat injection pass failed.\nIs the disk full?\n"));
+        }
+        for (size_t i = 0; i < str.size(); ++i) {
+            if (str[i] == '\n')
+                m_result.lines_ends.emplace_back(out_file_pos + i + 1);
+        }
+        out_file_pos += str.size();
+        str.clear();
+    };

    // Orca: read/split lines with EOL-preserving semantics (keep the original \r and \n bytes, and
    // synthesize no trailing newline). This is required for the empty-map identity: normalizing every
    // line ending to "\n" would not be byte-identical if the finished file used \r\n or lacked a
    // final newline.
    std::string gcode_line;
+    std::string export_buffer;
    unsigned int line_id = 0;
    auto op_it = inserted_operation_lines.begin();
    std::vector<char> buffer(65536 * 10, 0);
@@ -2038,14 +2058,16 @@ void GCodeProcessor::run_second_pass_injection()
                    }
                    ++op_it;
                }
-                writer.append(gcode_line);
+                export_buffer += gcode_line;
                gcode_line.clear();
+                if (export_buffer.length() >= 65536)
+                    write_out(export_buffer);
            }
        }
        if (eof)
            break;
    }
-    writer.flush();
+    write_out(export_buffer);

    out.close();
    in.close();
@@ -2616,6 +2638,12 @@ void GCodeProcessorResult::reset() {
    long_retraction_when_cut = false;
    timelapse_warning_code = 0;
    printable_height = 0.0f;
+    machine_frame_transform_active = false;
+    belt_tilt_angle = 0.f;
+    belt_z_origin   = 0.f;
+    preslice_remap_x = RemapAxis::PosX;
+    preslice_remap_y = RemapAxis::PosY;
+    preslice_remap_z = RemapAxis::PosZ;
    settings_ids.reset();
    filaments_count = 0;
    backtrace_enabled = false;
@@ -2852,6 +2880,32 @@ bool GCodeProcessor::check_multi_extruder_gcode_valid(const int
        return ps;
    };

+    // Belt-printer post-gcode shear/scale/post_remap is applied as the final
+    // step of BeltKinematics::to_machine, so MoveVertex.position is
+    // in the printer's machine frame.  Undo it here so the XY area check
+    // operates in the build-volume frame that printable_area is defined in
+    // (the height checks below are skipped on belt printers).  For non-belt printers
+    // (is_active() == false) apply_inverse is identity and behaviour is
+    // unchanged from before.
+    const bool machine_frame_active = m_machine_frame_transform.is_active();
+    auto compare_pos = [&](const GCodeProcessorResult::MoveVertex &move) -> Vec3d {
+        Vec3d pos = move.position.cast<double>();
+        if (!machine_frame_active)
+            return pos;
+        Vec3d extruder_off = Vec3d::Zero();
+        if (size_t(move.extruder_id) < m_extruder_offsets.size())
+            extruder_off = m_extruder_offsets[move.extruder_id].cast<double>();
+        // Strip plate + extruder offsets to recover the raw machine-frame
+        // coordinate that was emitted into the G-code (see store_move_vertex).
+        Vec3d machine(pos.x() - m_x_offset - extruder_off.x(),
+                      pos.y() - m_y_offset - extruder_off.y(),
+                      pos.z() - extruder_off.z() + m_z_offset);
+        Vec3d build = m_machine_frame_transform.apply_inverse(machine);
+        // Re-apply plate offset so the result matches plate_printable_poly,
+        // which is translated by plate_offset below.
+        return Vec3d(build.x() + m_x_offset, build.y() + m_y_offset, build.z());
+    };
+
    struct GCodePosInfo
    {
        Points pos;
@@ -2863,26 +2917,20 @@ bool GCodeProcessor::check_multi_extruder_gcode_valid(const int
    for (const GCodeProcessorResult::MoveVertex &move : m_result.moves) {
        // sometimes, the start line extrude was outside the edge of plate a little, this is allowed, so do not include into the gcode_path_pos
        if (move.type == EMoveType::Extrude /* && move.extrusion_role != ExtrusionRole::erFlush || move.type == EMoveType::Travel*/) {
+            const Vec3d cp = compare_pos(move);
+            // For belt printers we read Z from the inverse-transformed position
+            // (post-origin-snap, pre-machine-frame).  Otherwise keep the
+            // original print_z source (the slicer's layer-Z comment) so
+            // non-belt behaviour is bit-for-bit unchanged.
+            const float z_for_height = machine_frame_active ? float(cp.z()) : move.print_z;
            if (move.extrusion_role == ExtrusionRole::erCustom) {
-                /*if (move.is_arc_move_with_interpolation_points()) {
-                    for (int i = 0; i < move.interpolation_points.size(); i++) {
-                        gcode_path_pos[move.object_label_id][int(move.extruder_id)].pos_custom.emplace_back(to_2d(move.interpolation_points[i].cast<double>()));
-                    }
-                } else {*/
-                    gcode_path_pos[move.object_label_id][int(move.extruder_id)].pos_custom.emplace_back(to_2d(move.position.cast<double>()));
-                //}
+                gcode_path_pos[move.object_label_id][int(move.extruder_id)].pos_custom.emplace_back(to_2d(cp));
                gcode_path_pos[move.object_label_id][int(move.extruder_id)].max_print_z_custom =
-                    std::max(gcode_path_pos[move.object_label_id][int(move.extruder_id)].max_print_z_custom, move.print_z);
+                    std::max(gcode_path_pos[move.object_label_id][int(move.extruder_id)].max_print_z_custom, z_for_height);
            } else {
-                /*if (move.is_arc_move_with_interpolation_points()) {
-                    for (int i = 0; i < move.interpolation_points.size(); i++) {
-                        gcode_path_pos[move.object_label_id][int(move.extruder_id)].pos.emplace_back(to_2d(move.interpolation_points[i].cast<double>()));
-                    }
-                } else {*/
-                    gcode_path_pos[move.object_label_id][int(move.extruder_id)].pos.emplace_back(to_2d(move.position.cast<double>()));
-                //}
+                gcode_path_pos[move.object_label_id][int(move.extruder_id)].pos.emplace_back(to_2d(cp));
                gcode_path_pos[move.object_label_id][int(move.extruder_id)].max_print_z = std::max(gcode_path_pos[move.object_label_id][int(move.extruder_id)].max_print_z,
-                                                                                                   move.print_z);
+                                                                                                   z_for_height);
            }
        }
    }
@@ -2917,7 +2965,12 @@ bool GCodeProcessor::check_multi_extruder_gcode_valid(const int
                    valid = false;
                }
            }
-            if ( iter->second.max_print_z > plate_printable_height ) { //over height
+            // Belt printers: the Z recorded here grows with belt travel (machine Z with the
+            // frame transform, the slicing-frame Z without it), while printable_height is the
+            // clearance above the belt; the two are not comparable, so the over-height check
+            // is skipped, as the preview's ToolHeightOutside warning already is.
+            // Print::validate() checks the object's height against the clearance.
+            if ( !m_belt_printer && iter->second.max_print_z > plate_printable_height ) { //over height
                m_result.gcode_check_result.error_code |= (1 << 3);
                std::pair<int, int> filament_to_object_id;
                filament_to_object_id.first  = iter->first;
@@ -2958,7 +3011,7 @@ bool GCodeProcessor::check_multi_extruder_gcode_valid(const int
                    }

                // check printable height
-                if ((extruder_id < printable_heights.size()) && (iter->second.max_print_z > printable_heights[extruder_id])) {
+                if (!m_belt_printer && (extruder_id < printable_heights.size()) && (iter->second.max_print_z > printable_heights[extruder_id])) {
                    m_result.gcode_check_result.error_code |= (1 << 1);
                    std::pair<int, int> filament_to_object_id;
                    filament_to_object_id.first  = iter->first;
@@ -3124,6 +3177,13 @@ void GCodeProcessor::apply_config(const PrintConfig& config)

    m_result.printable_height = config.printable_height;

+    // Belt printer: cache the post-gcode machine-frame transform so the
+    // multi-extruder validator can undo it and compare against build-volume
+    // bounds rather than machine-frame positions.
+    m_machine_frame_transform.init_from_config(config);
+    m_result.machine_frame_transform_active = m_machine_frame_transform.is_active();
+    m_belt_printer = config.belt_printer.value;
+
    auto filament_maps = config.option<ConfigOptionInts>("filament_map");
    if (filament_maps != nullptr) {
        m_filament_maps = filament_maps->values;
@@ -3154,6 +3214,33 @@ void GCodeProcessor::apply_config(const DynamicPrintConfig& config)
 {
    m_parser.apply_config(config);

+    // Belt printer: remember the file's belt keys for export_config_for_render(). The
+    // config block lists belt_printer for every printer, so a non-belt file loaded while
+    // a belt printer is selected switches the preview's belt view off, and a belt file
+    // loaded on another printer brings its own tilt, remaps and bed along.
+    m_belt_render_config.clear();
+    {
+        const auto *belt = config.option<ConfigOptionBool>("belt_printer");
+        if (belt != nullptr) {
+            static const char *belt_keys[] = {
+                "belt_printer", "belt_slice_rotation", "belt_slice_rotation_angle", "belt_slice_rotation_global",
+                "belt_preslice_global", "preslice_remap_x", "preslice_remap_y", "preslice_remap_z", "preslice_remap_global",
+                "gcode_remap_x", "gcode_remap_y", "gcode_remap_z", "gcode_back_transform",
+                "belt_frame_tilt_decouple", "belt_frame_tilt_angle",
+            };
+            for (const char *key : belt_keys)
+                if (const ConfigOption *opt = config.option(key); opt != nullptr)
+                    m_belt_render_config.set_key_value(key, opt->clone());
+            // The Rev remaps mirror inside the build volume, so the designed view needs
+            // the bed the file was sliced for. Only a belt file may override it.
+            static const char *bed_keys[] = { "printable_area", "printable_height" };
+            if (belt->value)
+                for (const char *key : bed_keys)
+                    if (const ConfigOption *opt = config.option(key); opt != nullptr)
+                        m_belt_render_config.set_key_value(key, opt->clone());
+        }
+    }
+
    //BBS
    const ConfigOptionFloatsNullable* nozzle_volume = config.option<ConfigOptionFloatsNullable>("nozzle_volume");
    if (nozzle_volume != nullptr) {
@@ -3637,6 +3724,7 @@ void GCodeProcessor::reset()
    m_zero_layer_height = 0.0f;
    m_first_layer_height = 0.0f;
    m_processing_start_custom_gcode = false;
+    m_in_config_block = false;
    m_g1_line_id = 0;
    m_layer_id = 0;
    m_cp_color.reset();
@@ -3677,6 +3765,7 @@ DynamicConfig GCodeProcessor::export_config_for_render() const
    config.set_key_value("filament_is_support", new ConfigOptionBools(m_parser.get_config().filament_is_support.values));
    config.set_key_value("filament_type", new ConfigOptionStrings(m_parser.get_config().filament_type.values));
    config.set_key_value("filament_map", new ConfigOptionInts(m_parser.get_config().filament_map.values));
+    config.apply(m_belt_render_config);
    return config;
 }

@@ -4242,6 +4331,55 @@ void GCodeProcessor::process_tags(const std::string_view comment, bool producers
        return;
    }

+    if (boost::starts_with(comment, " CONFIG_BLOCK_START")) {
+        m_in_config_block = true;
+        return;
+    }
+    if (boost::starts_with(comment, " CONFIG_BLOCK_END")) {
+        m_in_config_block = false;
+        return;
+    }
+
+    // Belt printer: derive the physical tilt magnitude from the slicing-rotation
+    // angle header comment (used to enable the preview's belt view). Only the belt
+    // header carries it outside the config block; the config block lists the key
+    // for every printer, belt or not.
+    if (!m_in_config_block && boost::starts_with(comment, " belt_slice_rotation_angle = ")) {
+        try {
+            m_result.belt_tilt_angle = std::abs(std::stof(std::string(comment.substr(29))));
+        } catch (...) {}
+        return;
+    }
+    // Belt printer: parse pre-slice axis remap from header comments.
+    {
+        auto trim = [](const std::string &s) -> std::string {
+            size_t start = s.find_first_not_of(" \t\r\n");
+            size_t end   = s.find_last_not_of(" \t\r\n");
+            return (start == std::string::npos) ? "" : s.substr(start, end - start + 1);
+        };
+        // Pre-slice axis remap
+        auto parse_remap_axis = [](const std::string &s) -> RemapAxis {
+            if (s == "pos_x") return RemapAxis::PosX;
+            if (s == "pos_y") return RemapAxis::PosY;
+            if (s == "pos_z") return RemapAxis::PosZ;
+            if (s == "neg_x") return RemapAxis::NegX;
+            if (s == "neg_y") return RemapAxis::NegY;
+            if (s == "neg_z") return RemapAxis::NegZ;
+            if (s == "rev_x") return RemapAxis::RevX;
+            if (s == "rev_y") return RemapAxis::RevY;
+            if (s == "rev_z") return RemapAxis::RevZ;
+            return RemapAxis::PosX;
+        };
+        if (boost::starts_with(comment, " preslice_remap_x = ")) {
+            m_result.preslice_remap_x = parse_remap_axis(trim(std::string(comment.substr(20)))); return;
+        }
+        if (boost::starts_with(comment, " preslice_remap_y = ")) {
+            m_result.preslice_remap_y = parse_remap_axis(trim(std::string(comment.substr(20)))); return;
+        }
+        if (boost::starts_with(comment, " preslice_remap_z = ")) {
+            m_result.preslice_remap_z = parse_remap_axis(trim(std::string(comment.substr(20)))); return;
+        }
+    }
    // wipe start tag
    if (boost::starts_with(comment, reserved_tag(ETags::Wipe_Start))) {
        m_wiping = true;
@@ -6138,6 +6276,13 @@ void GCodeProcessor::process_G92(const GCodeReader::GCodeLine& line)
    if (line.has_z()) {
        m_origin[Z] = m_end_position[Z] - line.z() * lengths_scale_factor;
        any_found = true;
+        // Belt only: the start G-code's purge-blob advance + G92 Z0 resets leave a constant
+        // machine-Z origin offset here; the designed-view back-transform subtracts it so
+        // toolpaths map to the model's belt coordinate (gcode Z). Gated on belt_tilt_angle
+        // (set from the belt header, parsed before the body) so non-belt G-code processing
+        // is byte-identical — no unconditional work on the shared path.
+        if (m_result.belt_tilt_angle != 0.f)
+            m_result.belt_z_origin = m_origin[Z];
    }

    if (line.has_e()) {
@@ -7116,6 +7261,22 @@ void GCodeProcessor::store_move_vertex(EMoveType type, EMovePathType path_type,
        m_result.print_statistics.total_travel_distance += m_travel_dist;
    }

+    // During the start G-code "prepare" stage the toolhead Z is not yet a real
+    // print height on a normal printer, so it is pinned to the first-layer height
+    // to keep the preview tidy. Belt printers are the exception: there the Z is
+    // written explicitly by the belt kinematics and the designed-view back-transform
+    // couples machine Z into the rendered model Y (the belt tilt mixes the height
+    // and belt-feed axes). Overriding Z therefore back-transforms the last
+    // prepare-stage move (the unretract before the first extrusion) to model
+    // Y ~= 0, and the libvgcode path builder then draws a phantom extrusion
+    // segment from Y ~= 0 to the first real toolpath. Keep the real Z for belt
+    // printers so prepare-stage moves map correctly. Gated on belt_tilt_angle (set
+    // from the G-code header before the body is processed) so non-belt processing
+    // is byte-identical.
+    const float store_z = (m_processing_start_custom_gcode && m_result.belt_tilt_angle == 0.f)
+        ? m_first_layer_height
+        : m_end_position[Z] - m_z_offset;
+
    m_result.moves.push_back({
        m_last_line_id,
        type,
@@ -7123,7 +7284,7 @@ void GCodeProcessor::store_move_vertex(EMoveType type, EMovePathType path_type,
        static_cast<unsigned char>(filament_id),
        m_cp_color.current,
        //BBS: add plate's offset to the rendering vertices
-        Vec3f(m_end_position[X] + m_x_offset, m_end_position[Y] + m_y_offset, m_processing_start_custom_gcode ? m_first_layer_height : m_end_position[Z]- m_z_offset) + m_extruder_offsets[filament_id],
+        Vec3f(m_end_position[X] + m_x_offset, m_end_position[Y] + m_y_offset, store_z) + m_extruder_offsets[filament_id],
        static_cast<float>(m_end_position[E] - m_start_position[E]),
        m_feedrate,
        0.0f, // actual feedrate
@@ -12,6 +12,7 @@
 #include "libslic3r/PrintConfig.hpp"
 #include "libslic3r/CustomGCode.hpp"
 #include "libslic3r/MultiNozzleUtils.hpp"
+#include "libslic3r/GCode/MachineFrameTransform.hpp"

 #include <cstddef>
 #include <cassert>
@@ -290,6 +291,22 @@ class Print;
        bool support_traditional_timelapse{true};
        float printable_height;
        float z_offset;
+        // Belt printer: physical tilt magnitude (deg) parsed from the slicing-rotation
+        // header comment; used to enable the preview's belt view.
+        float belt_tilt_angle{ 0.f };
+        // Belt printer: machine-Z origin offset (mm) left in m_origin[Z] by the start
+        // G-code (purge-blob belt advance + G92 Z0 resets). Move positions are stored
+        // as gcode_Z + this offset, so the designed-view back-transform must subtract it
+        // to recover the model's belt coordinate.
+        float belt_z_origin{ 0.f };
+        // Belt printer: post-gcode shear/scale/post_remap is configured and
+        // non-identity.  When set, the layer Z values in `moves` are in the
+        // machine frame and should not be compared against `printable_height`
+        // (which lives in the build-volume frame).
+        bool machine_frame_transform_active{ false };
+        RemapAxis preslice_remap_x{ RemapAxis::PosX };
+        RemapAxis preslice_remap_y{ RemapAxis::PosY };
+        RemapAxis preslice_remap_z{ RemapAxis::PosZ };
        SettingsIds settings_ids;
        size_t filaments_count;
        bool backtrace_enabled;
@@ -385,6 +402,12 @@ class Print;
            // Keep the SKIPPABLE per-type time on a copied result.
            skippable_part_time = std::forward<Other>(other).skippable_part_time;
            initial_layer_time = std::forward<Other>(other).initial_layer_time;
+            belt_tilt_angle = std::forward<Other>(other).belt_tilt_angle;
+            belt_z_origin = std::forward<Other>(other).belt_z_origin;
+            machine_frame_transform_active = std::forward<Other>(other).machine_frame_transform_active;
+            preslice_remap_x = std::forward<Other>(other).preslice_remap_x;
+            preslice_remap_y = std::forward<Other>(other).preslice_remap_y;
+            preslice_remap_z = std::forward<Other>(other).preslice_remap_z;
 #if ENABLE_GCODE_VIEWER_STATISTICS
            time = std::forward<Other>(other).time;
 #endif
@@ -491,9 +514,6 @@ class Print;
        static const std::string VFlush_End_Tag;
        static const std::string External_Purge_Tag;
    public:
-        // Size of the blocks the post-processing passes write the G-code in
-        static constexpr size_t Output_Block_Size = 65536;
-
        // Orca: SKIPPABLE region tags, stored as static strings (the FLUSH idiom above) rather than
        // a CustomETags/CustomTags array. Public so the emission sites (WipeTower / change_filament
        // path) can reference them single-sourced.
@@ -1085,6 +1105,10 @@ class Print;
    private:
        CommandProcessor m_command_processor;
        GCodeReader m_parser;
+        // Belt printer: the belt keys of the loaded file's config block (plus the bed they
+        // are relative to), handed to the preview through export_config_for_render() so the
+        // belt view and its back-transform follow the file, not the selected printer.
+        DynamicConfig m_belt_render_config;
        EUnits m_units;
        EPositioningType m_global_positioning_type;
        EPositioningType m_e_local_positioning_type;
@@ -1160,6 +1184,13 @@ class Print;
        double          m_x_offset{ 0 };
        double          m_y_offset{ 0 };

+        // Belt-printer post-gcode shear/scale/post_remap. Used by
+        // check_multi_extruder_gcode_valid to undo the machine-frame
+        // transform on move positions so bounds checks operate in the
+        // pre-machine-frame (build-volume) frame.
+        MachineFrameTransform m_machine_frame_transform;
+        bool                  m_belt_printer{ false };
+
        unsigned int m_line_id;
        unsigned int m_last_line_id;
        float m_feedrate; // mm/s
@@ -1189,6 +1220,7 @@ class Print;
        float m_first_layer_height; // mm
        float m_zero_layer_height; // mm
        bool m_processing_start_custom_gcode;
+        bool m_in_config_block;
        unsigned int m_g1_line_id;
        unsigned int m_layer_id;
        CpColor m_cp_color;
@@ -0,0 +1,89 @@
+#include "MachineFrameTransform.hpp"
+#include "../Geometry.hpp"
+#include "../Point.hpp"
+#include "../PrintConfig.hpp"
+#include "../libslic3r.h"
+
+#include <cmath>
+
+namespace Slic3r {
+
+bool MachineFrameTransform::init_from_config(const PrintConfig &config)
+{
+    m_active            = false;
+    m_transform         = Transform3d::Identity();
+    m_transform_inverse = Transform3d::Identity();
+
+    if (!config.belt_printer.value)
+        return false;
+
+    // The machine-frame transform is derived from the single belt tilt (axis +
+    // angle) that also drives the pre-slice mesh rotation.  Expert decouple lets
+    // the machine-frame angle differ from the slicing rotation; otherwise both
+    // use belt_slice_rotation_angle.
+    const BeltRotationAxis axis = config.belt_slice_rotation.value;
+    if (axis == BeltRotationAxis::None || axis == BeltRotationAxis::Z)
+        return false; // Z is an in-plane spin: no machine-frame tilt.
+
+    const double angle_deg = config.belt_frame_tilt_decouple.value
+        ? config.belt_frame_tilt_angle.value
+        : config.belt_slice_rotation_angle.value;
+    if (std::abs(angle_deg) <= EPSILON)
+        return false;
+
+    const double angle_rad = Geometry::deg2rad(angle_deg);
+    const double sin_a      = std::sin(angle_rad);
+    if (std::abs(sin_a) <= EPSILON)
+        return false;
+    const double cot_a   = std::cos(angle_rad) / sin_a;
+    const double inv_sin = 1.0 / std::abs(sin_a);
+
+    // This stage runs after the conventional belt axis swap. For an X-axis
+    // slicing rotation, remapped Y is model height and remapped Z is travel
+    // along the belt. Convert those Cartesian coordinates to machine axes with
+    // the established belt-printer convention:
+    //   machine gantry = model height / sin(a)
+    //   machine belt   = model belt + model height * cot(a)
+    // The Y-rotation case is the same mapping on X/Z, with the rotation sign.
+    // At 45 degrees tan/cot and sin/cos are equal, which previously hid the
+    // incorrect complementary-angle formulas used by this unified transform.
+    Matrix3d shear = Matrix3d::Identity();
+    Matrix3d scale = Matrix3d::Identity();
+    if (axis == BeltRotationAxis::X) {
+        shear(2, 1) =  cot_a;   // Z from Y
+        scale(1, 1) =  inv_sin; // Y
+    } else { // BeltRotationAxis::Y
+        shear(2, 0) = -cot_a;   // Z from X
+        scale(0, 0) =  inv_sin; // X
+    }
+
+    // Apply shear first, then scale (the historical default ShearThenScale order:
+    // result = scale * shear * p).  For the canonical 45°/X belt this maps
+    // (x,y,z) -> (x, y/sin, y + z), matching the previous per-axis config.
+    Transform3d combined = Transform3d::Identity();
+    combined.linear() = scale * shear;
+
+    if (combined.isApprox(Transform3d::Identity()))
+        return false;
+
+    m_transform         = combined;
+    m_transform_inverse = combined.inverse();
+    m_active            = true;
+    return true;
+}
+
+Vec3d MachineFrameTransform::apply(const Vec3d &pos) const
+{
+    if (!m_active)
+        return pos;
+    return m_transform * pos;
+}
+
+Vec3d MachineFrameTransform::apply_inverse(const Vec3d &pos) const
+{
+    if (!m_active)
+        return pos;
+    return m_transform_inverse * pos;
+}
+
+} // namespace Slic3r
@@ -0,0 +1,54 @@
+#ifndef slic3r_MachineFrameTransform_hpp_
+#define slic3r_MachineFrameTransform_hpp_
+
+#include "../libslic3r.h"
+#include "../Point.hpp"
+#include "../PrintConfig.hpp"
+
+namespace Slic3r {
+
+// Post-stage machine-frame transform for belt printers.
+//
+// Applied in BeltKinematics::to_machine AFTER the back-transform and
+// the gcode_remap_* axis remap.  Maps Cartesian (axis-permuted) G-code
+// coordinates into the printer's physical machine frame.
+//
+// Derived entirely from the single belt tilt (belt_slice_rotation axis +
+// belt_slice_rotation_angle): a shear coupling the height axis to the belt-feed
+// axis (factor cot a) plus a 1/sin a scale on the gantry-height axis.  The expert
+// belt_frame_tilt_decouple flag lets the machine-frame angle differ from the
+// pre-slice rotation angle via belt_frame_tilt_angle.
+class MachineFrameTransform
+{
+public:
+    MachineFrameTransform() = default;
+
+    // Initialize from belt printer config.  Returns true if a non-identity
+    // transform was computed.  Inactive when belt_printer is disabled or
+    // both shear and scale are identity.
+    bool init_from_config(const PrintConfig &config);
+
+    // Apply the transform to a point.  Returns pos unchanged if not active.
+    Vec3d apply(const Vec3d &pos) const;
+
+    // Apply the inverse transform.  Returns pos unchanged if not active.
+    // Used by validators that need to compare emitted machine-frame
+    // coordinates against build-volume bounds.
+    Vec3d apply_inverse(const Vec3d &pos) const;
+
+    bool is_active() const { return m_active; }
+
+    // The composed shear*scale transform (identity when inactive). Exposed so the
+    // G-code viewer can build the machine->model back-transform for the upright
+    // ("designed") belt preview.
+    const Transform3d& transform() const { return m_transform; }
+
+private:
+    bool        m_active            = false;
+    Transform3d m_transform         = Transform3d::Identity();
+    Transform3d m_transform_inverse = Transform3d::Identity();
+};
+
+} // namespace Slic3r
+
+#endif // slic3r_MachineFrameTransform_hpp_
@@ -0,0 +1,48 @@
+#include "MachineKinematics.hpp"
+#include "../Point.hpp"
+
+namespace Slic3r {
+
+// Moved verbatim from GCodeWriter::apply_axis_remap().
+Vec3d CartesianKinematics::apply_axis_remap(const Vec3d &pos) const
+{
+    if (!has_axis_remap())
+        return pos;
+    auto remap = [this, &pos](int r) -> double {
+        int axis = r % 3;
+        if (r < 3) return pos[axis];
+        if (r < 6) return -pos[axis];
+        return m_build_vol_max[axis] - pos[axis];
+    };
+    return { remap(m_remap_x), remap(m_remap_y), remap(m_remap_z) };
+}
+
+// Inverse of the above.  Output axis i is fed by source axis (r_i % 3); walking
+// the three outputs therefore fills every source component exactly once, so long
+// as the remap is a permutation (which set_axis_remap callers guarantee).
+Vec3d CartesianKinematics::apply_axis_remap_inverse(const Vec3d &machine) const
+{
+    if (!has_axis_remap())
+        return machine;
+    Vec3d out = Vec3d::Zero();
+    const int r[3] = { m_remap_x, m_remap_y, m_remap_z };
+    for (int i = 0; i < 3; ++i) {
+        const int axis = r[i] % 3;
+        if (r[i] < 3)      out[axis] = machine[i];
+        else if (r[i] < 6) out[axis] = -machine[i];
+        else               out[axis] = m_build_vol_max[axis] - machine[i];
+    }
+    return out;
+}
+
+Vec3d CartesianKinematics::to_machine(const Vec3d &p) const
+{
+    return this->apply_axis_remap(p);
+}
+
+Vec3d CartesianKinematics::to_logical(const Vec3d &machine) const
+{
+    return this->apply_axis_remap_inverse(machine);
+}
+
+} // namespace Slic3r
@@ -0,0 +1,106 @@
+#ifndef slic3r_MachineKinematics_hpp_
+#define slic3r_MachineKinematics_hpp_
+
+#include "../Point.hpp"
+
+namespace Slic3r {
+
+// The frame contract for emitted movement.
+//
+// GCodeWriter produces points in the *logical placed* frame: plate offsets have
+// already been subtracted, but no machine-specific mapping has been applied.
+// A MachineKinematics turns that into the coordinates actually written to
+// G-code, and answers the two structural questions the writer needs in order to
+// decide which axis words it may omit.
+//
+// This is a seam for writer-generated movement only.  Start/end/custom G-code,
+// classic wipe-tower output and GCodeWriter::extrude_arc_to_xy() do NOT pass
+// through it: they write machine coordinates directly.
+class MachineKinematics
+{
+public:
+    virtual ~MachineKinematics() = default;
+
+    // Logical placed point -> emitted machine point.
+    virtual Vec3d to_machine(const Vec3d &p) const = 0;
+
+    // Inverse of to_machine(), back to the logical placed frame.  Intended for
+    // consumers that must reconstruct model coordinates from emitted G-code
+    // (the G-code viewer's upright preview).
+    virtual Vec3d to_logical(const Vec3d &machine) const = 0;
+
+    // Machine point -> build-volume frame, for bounds validation only.  This is
+    // deliberately NOT to_logical(): the build-volume check wants the physical
+    // frame the printable area is expressed in, not the model frame.  Keeping
+    // them separate stops the two contracts from being confused.
+    virtual Vec3d to_build_volume(const Vec3d &machine) const = 0;
+
+    // True when a move must emit X, Y and Z because omitting a word would be
+    // wrong under this mapping.  Deliberately not called "couples_axes": a pure
+    // axis permutation forces full emission without physically coupling axes.
+    virtual bool must_emit_all_axes() const = 0;
+
+    // True when a lift must be suppressed while the current position is unknown,
+    // because _travel_to_z() re-emits the logical X/Y through this mapping and an
+    // uninitialised position would map to a bogus machine point -- for a reverse
+    // mapping, the far corner of the bed.
+    virtual bool suppress_lift_at_unknown_position() const = 0;
+
+    // True when a G2/G3 arc in the logical XY plane is still the same arc in the
+    // machine frame. Arc moves emit only X, Y, I and J, so this asks a narrower
+    // question than must_emit_all_axes(): whether logical X and Y reach the
+    // machine unchanged. A mapping that only negates or reverses Z keeps its
+    // arcs; one that permutes X or Y moves the arc out of the plane that I/J
+    // describes, and a shear turns the circle into an ellipse G2/G3 cannot
+    // express at all.
+    virtual bool supports_arc_moves() const = 0;
+
+    // Configuration.  GCodeWriter forwards its setters here so that the state
+    // lives with the strategy and a strategy installed before the setters run
+    // still receives it.
+    virtual void set_axis_remap(int rx, int ry, int rz) = 0;
+    virtual void set_build_volume_max(const Vec3d &max) = 0;
+};
+
+// Axis remap only -- the historical GCodeWriter behaviour, moved verbatim.
+//
+// The remap encodes, per output axis, which source axis feeds it and how:
+//   r < 3 : source axis r, unchanged
+//   r < 6 : source axis r-3, negated
+//   else  : source axis r-6, reversed within the build volume
+class CartesianKinematics : public MachineKinematics
+{
+public:
+    Vec3d to_machine(const Vec3d &p) const override;
+    Vec3d to_logical(const Vec3d &machine) const override;
+    Vec3d to_build_volume(const Vec3d &machine) const override { return machine; }
+
+    bool must_emit_all_axes() const override { return this->has_axis_remap(); }
+    bool suppress_lift_at_unknown_position() const override { return this->has_axis_remap(); }
+
+    // X and Y must reach the machine untouched. Because the remap is a
+    // permutation, pinning those two also pins Z to Z, so a mapping that only
+    // negates or reverses Z still supports arcs -- every word a G2/G3 emits is
+    // unchanged by it.
+    bool supports_arc_moves() const override { return m_remap_x == 0 && m_remap_y == 1; }
+
+    void set_axis_remap(int rx, int ry, int rz) override
+        { m_remap_x = rx; m_remap_y = ry; m_remap_z = rz; }
+    void set_build_volume_max(const Vec3d &max) override { m_build_vol_max = max; }
+
+    bool has_axis_remap() const
+        { return m_remap_x != 0 || m_remap_y != 1 || m_remap_z != 2; }
+
+protected:
+    Vec3d apply_axis_remap(const Vec3d &pos) const;
+    Vec3d apply_axis_remap_inverse(const Vec3d &pos) const;
+
+    int   m_remap_x { 0 };
+    int   m_remap_y { 1 };
+    int   m_remap_z { 2 };
+    Vec3d m_build_vol_max { Vec3d::Zero() };
+};
+
+} // namespace Slic3r
+
+#endif // slic3r_MachineKinematics_hpp_
@@ -706,7 +706,7 @@ void compute_global_occlusion(GlobalModelInfo &result, const PrintObject *po,
                              SeamPosition seam_position = spAligned) {
  BOOST_LOG_TRIVIAL(debug)
      << "SeamPlacer: gather occlusion meshes: start";
-  auto obj_transform = po->trafo_centered();
+  auto obj_transform = po->trafo_sliced();
  indexed_triangle_set triangle_set;
  indexed_triangle_set negative_volumes_set;
  //add all parts
@@ -796,7 +796,7 @@ void gather_enforcers_blockers(GlobalModelInfo &result, const PrintObject *po) {
  BOOST_LOG_TRIVIAL(debug)
      << "SeamPlacer: build AABB trees for raycasting enforcers/blockers: start";

-  auto obj_transform = po->trafo_centered();
+  auto obj_transform = po->trafo_sliced();

  for (const ModelVolume *mv : po->model_object()->volumes) {
    // Collect painting only from model parts (what the gizmo edits) and negative volumes (the only way
@@ -18,6 +18,7 @@
 #include "Utils.hpp"
 #include "format.hpp"
 #include "I18N.hpp"
+#include "../BeltBrim.hpp"

 #include <boost/log/trivial.hpp>
 #include <vector>
@@ -419,6 +420,10 @@ bool ToolOrdering::insert_wipe_tower_extruder()
 {
    if (!m_print_config_ptr || !m_print_config_ptr->enable_prime_tower)
        return false;
+    // Belt mode has no classic wipe tower; the dedicated wipe tower filament
+    // must not inject extra toolchanges into the purge prism planning.
+    if (m_print_config_ptr->belt_printer)
+        return false;
    if (m_print_config_ptr->wipe_tower_filament == 0)
        return false;

@@ -516,6 +521,11 @@ ToolOrdering::ToolOrdering(const PrintObject &object, unsigned int first_extrude
            zs.emplace_back(layer->print_z);
        for (auto layer : object.support_layers())
            zs.emplace_back(layer->print_z);
+        // Belt brim apron bands sit below the object's first layer and have no
+        // layer of their own, but tools_for_layer() asserts an exact Z match, so
+        // their print_z must be part of the ordering.
+        for (const BeltBrimBand &band : object.belt_brim_prologue())
+            zs.emplace_back(band.print_z);
        this->initialize_layers(zs);
    }

@@ -560,6 +570,10 @@ ToolOrdering::ToolOrdering(const Print &print, unsigned int first_extruder, bool
                zs.emplace_back(layer->print_z);
            for (auto layer : object->support_layers())
                zs.emplace_back(layer->print_z);
+            // See the single-object ctor: belt brim apron bands need their own
+            // ordering entries or tools_for_layer() will assert.
+            for (const BeltBrimBand &band : object->belt_brim_prologue())
+                zs.emplace_back(band.print_z);

            max_layer_height = std::max(max_layer_height, object->config().layer_height.value);
        }
@@ -994,6 +1008,44 @@ void ToolOrdering::collect_extruders(const PrintObject &object, const std::vecto
        }
    }

+    // Belt brim apron bands own their layers outright: they print below the
+    // object's first layer, so no object or support layer claims an extruder there
+    // and process_layer() would bail out at "Nothing to extrude".  Claim the
+    // object's outer wall filament, in the same raw 1-based domain the loops above
+    // push.  Deliberately not layer_tools.has_object, which drives skirt marking
+    // and wiping overrides.
+    if (! object.belt_brim_prologue().empty()) {
+        // 1-based, same domain the object/support pushes above use; reindexed to 0-based
+        // with the rest of the list later.
+        const unsigned int brim_filament = object.belt_brim_filament();
+        for (const BeltBrimBand &band : object.belt_brim_prologue()) {
+            if (band.fills.empty())
+                continue;
+            LayerTools &layer_tools = this->tools_for_layer(band.print_z);
+            layer_tools.extruders.push_back(brim_filament);
+            layer_tools.has_belt_brim = true;
+        }
+    }
+
+    // Coincident brim bands (belt_brim_by_layer) print ON an object layer rather than
+    // below it, but that layer can produce no InstanceVisit in process_layer - a
+    // zero-extrusion lead-in slice with no coinciding support - and the band would then
+    // be silently dropped.  Register the brim filament on every layer that carries a
+    // coincident band, in the same 1-based domain as the prologue push above, so a brim
+    // pass always exists there.
+    if (object.has_belt_brim()) {
+        const unsigned int brim_filament = object.belt_brim_filament();
+        const auto        &by_layer      = object.belt_brim_by_layer();
+        const size_t       n             = std::min(by_layer.size(), object.layers().size());
+        for (size_t i = 0; i < n; ++ i) {
+            if (by_layer[i].empty())
+                continue;
+            LayerTools &layer_tools = this->tools_for_layer(object.layers()[i]->print_z);
+            layer_tools.extruders.push_back(brim_filament);
+            layer_tools.has_belt_brim = true;
+        }
+    }
+
    for (auto& layer : m_layer_tools) {
        // Sort and remove duplicates
        sort_remove_duplicates(layer.extruders);
@@ -1036,12 +1088,28 @@ void ToolOrdering::fill_wipe_tower_partitions(const PrintConfig &config, coordf_
    }

    //FIXME this is a hack to get the ball rolling.
+    // The `print_z < object_bottom_z` clause reads "below the object" as "raft
+    // gap".  On a belt printer that is wrong: the brim apron legitimately prints
+    // below the object's first layer, and treating those layers as raft would put a
+    // wipe tower at negative Z.  A belt printer never prints the classic
+    // prime tower (Print::has_wipe_tower()), so simply drop the clause there.
+    //
+    // Gate on config.belt_printer, NOT on has_belt_brim: every layer below the
+    // object bottom on a belt printer is legitimately a sub-object stream - brim
+    // apron, belt support printed below Z0, or the object's own lead-in - and none of
+    // them is ever raft, because Print::validate() rejects raft_layers>0 on a belt
+    // printer outright.  Narrowing this to has_belt_brim would reclassify
+    // belt-support-below-floor layers as raft on brim-less belt prints and reintroduce
+    // the negative-Z wipe tower, so the broad belt_printer gate is correct.
+    const bool belt_no_raft_gap = config.belt_printer.value;
    for (LayerTools &lt : m_layer_tools)
        lt.has_wipe_tower |= ((lt.has_object || lt.has_support) && (config.timelapse_type == TimelapseType::tlSmooth || lt.wipe_tower_partitions > 0))
-            || lt.print_z < object_bottom_z + EPSILON;
+            || (! belt_no_raft_gap && lt.print_z < object_bottom_z + EPSILON);

    // Test for a raft, insert additional wipe tower layer to fill in the raft separation gap.
-    for (size_t i = 0; i + 1 < m_layer_tools.size(); ++ i) {
+    // Skipped on belt printers for the same reason as the clause above: layers
+    // below the object are brim apron, not raft.
+    for (size_t i = 0; ! belt_no_raft_gap && i + 1 < m_layer_tools.size(); ++ i) {
        const LayerTools &lt      = m_layer_tools[i];
        const LayerTools &lt_next = m_layer_tools[i + 1];
        if (lt.print_z < object_bottom_z + EPSILON && lt_next.print_z >= object_bottom_z + EPSILON) {
@@ -84,7 +84,17 @@ public:

    void set_layer_tools_ptr(const LayerTools* lt) { m_layer_tools = lt; }

+    // Returns true if entity is not printed with its usual extruder for a given
+    // copy -- i.e. it was claimed as a wiping/purge extrusion. Public because the
+    // belt purge prism uses it to tell which of its fills actually carry purge
+    // from the ones that are unclaimed waste (Print::_plan_belt_purge()).
+    bool is_entity_overridden(const ExtrusionEntity* entity, const PrintObject *object, size_t copy_id) const {
+        auto it = entity_map.find(std::make_tuple(entity, object));
+        return it != entity_map.end() && copy_id < it->second.size() && it->second[copy_id] != -1;
+    }
+
 private:
+
    int first_nonsoluble_extruder_on_layer(const PrintConfig& print_config) const;
    int last_nonsoluble_extruder_on_layer(const PrintConfig& print_config) const;

@@ -94,12 +104,6 @@ private:
    void set_support_extruder_override(const PrintObject* object, size_t copy_id, int extruder, size_t num_of_copies);
    void set_support_interface_extruder_override(const PrintObject* object, size_t copy_id, int extruder, size_t num_of_copies);

-    // Returns true in case that entity is not printed with its usual extruder for a given copy:
-    bool is_entity_overridden(const ExtrusionEntity* entity, const PrintObject *object, size_t copy_id) const {
-        auto it = entity_map.find(std::make_tuple(entity, object));
-        return it == entity_map.end() ? false : it->second[copy_id] != -1;
-    }
-
    std::map<std::tuple<const ExtrusionEntity*, const PrintObject *>, ExtruderPerCopy> entity_map;  // to keep track of who prints what
    // BBS
    std::map<const PrintObject*, int> support_map;
@@ -175,6 +179,10 @@ public:
    // Should a skirt be printed at this layer?
    // Layers are marked for infinite skirt aka draft shield. Not all the layers have to be printed.
    bool                        has_skirt = false;
+    // Belt printers: is this one of the brim-only apron layers below the object's
+    // first layer?  Kept separate from has_object so skirt marking and wiping
+    // overrides are unaffected.
+    bool                        has_belt_brim = false;
    // Will there be anything extruded on this layer for the wipe tower?
    // Due to the support layers possibly interleaving the object layers,
    // wipe tower will be disabled for some support only layers.
@@ -1,6 +1,7 @@
 #include "GCodeWriter.hpp"
 #include "Config.hpp"
 #include "Extruder.hpp"
+#include "Geometry.hpp"
 #include "I18N.hpp"
 #include "Point.hpp"
 #include "Polygon.hpp"
@@ -31,6 +32,7 @@
 #include <sstream>
 #include <stdexcept>
 #include <math.h>
+#include <memory>

 #ifdef __APPLE__
    #include <boost/spirit/include/karma.hpp>
@@ -43,6 +45,57 @@ namespace Slic3r {

 bool GCodeWriter::full_gcode_comment = true;

+// A lift emitted through _travel_to_z() re-emits the stored logical X/Y under a
+// mapping that must emit every axis. While the position is unknown that X/Y is
+// the uninitialised origin, which maps to a real but wrong machine point, so the
+// lift has to be skipped rather than commanded.
+bool GCodeWriter::must_skip_lift_now() const
+{
+    return m_kinematics->suppress_lift_at_unknown_position() && ! this->is_current_position_clear();
+}
+
+bool GCodeWriter::point_on_first_layer(const Vec3d &point_logical) const
+{
+    if (m_first_layer_point_test)
+        return m_first_layer_point_test(point_logical);
+    return m_is_first_layer;
+}
+
+void GCodeWriter::set_axis_remap(int rx, int ry, int rz)
+{
+    m_remap_x = rx;
+    m_remap_y = ry;
+    m_remap_z = rz;
+    m_kinematics->set_axis_remap(rx, ry, rz);
+}
+
+void GCodeWriter::set_build_volume_max(const Vec3d &max)
+{
+    m_build_vol_max = max;
+    m_kinematics->set_build_volume_max(max);
+}
+
+void GCodeWriter::set_kinematics(std::unique_ptr<MachineKinematics> kinematics)
+{
+    assert(kinematics);
+    m_kinematics = std::move(kinematics);
+    // Replay whatever was configured on the previous strategy so callers may
+    // install the kinematics before or after set_axis_remap/set_build_volume_max.
+    m_kinematics->set_axis_remap(m_remap_x, m_remap_y, m_remap_z);
+    m_kinematics->set_build_volume_max(m_build_vol_max);
+}
+
+// Kept as the writer-facing name for "this move must emit every axis word".
+bool GCodeWriter::has_axis_remap() const
+{
+    return m_kinematics->must_emit_all_axes();
+}
+
+Vec3d GCodeWriter::apply_axis_remap(const Vec3d &pos) const
+{
+    return m_kinematics->to_machine(pos);
+}
+
 bool GCodeWriter::supports_separate_travel_acceleration(GCodeFlavor flavor)
 {
    return (flavor == gcfRepetier || flavor == gcfMarlinFirmware ||  flavor == gcfRepRapFirmware);
@@ -796,8 +849,14 @@ std::string GCodeWriter::travel_to_xy(const Vec2d &point, const std::string &com
    Vec2d point_on_plate = { point(0) - m_x_offset, point(1) - m_y_offset };

    GCodeG1Formatter w;
-    w.emit_xy(point_on_plate);
-    auto speed = m_is_first_layer
+    if (has_axis_remap()) {
+        // Axis remap may couple XY with Z; emit full XYZ in machine coordinates.
+        Vec3d machine = apply_axis_remap(Vec3d(point_on_plate.x(), point_on_plate.y(), m_pos.z()));
+        w.emit_xyz(machine);
+    } else {
+        w.emit_xy(point_on_plate);
+    }
+    auto speed = this->point_on_first_layer(Vec3d(point_on_plate.x(), point_on_plate.y(), m_pos.z()))
        ? this->config.get_abs_value_at("initial_layer_travel_speed", m_cached_extruder_idx) : this->config.travel_speed.get_at(m_cached_extruder_idx);
    w.emit_f(speed * 60.0);
    //BBS
@@ -810,6 +869,8 @@ it will not perform subsequent lifts, even if Z was raised manually
 (i.e. with travel_to_z()) and thus _lifted was reduced. */
 std::string GCodeWriter::lazy_lift(LiftType lift_type, bool spiral_vase)
 {
+    if (m_force_normal_lift)
+        lift_type = LiftType::NormalLift;
    // check whether the above/below conditions are met
    double target_lift = 0;
    {
@@ -824,6 +885,10 @@ std::string GCodeWriter::lazy_lift(LiftType lift_type, bool spiral_vase)
    // BBS
    if (m_lifted == 0 && m_to_lift == 0 && target_lift > 0) {
        if (spiral_vase) {
+            if (this->must_skip_lift_now())
+                // Record no lift, so a later unlift() does not descend from a
+                // height that was never commanded.
+                return "";
            m_lifted = target_lift;
            return this->_travel_to_z(m_pos(2) + target_lift, "lift Z");
        }
@@ -836,8 +901,9 @@ std::string GCodeWriter::lazy_lift(LiftType lift_type, bool spiral_vase)
 }

 // BBS: immediately execute an undelayed lift move with a spiral lift pattern
-// designed specifically for subsequent gcode injection (e.g. timelapse) 
+// designed specifically for subsequent gcode injection (e.g. timelapse)
 std::string GCodeWriter::eager_lift(const LiftType type) {
+    const LiftType effective_type = m_force_normal_lift ? LiftType::NormalLift : type;
    std::string lift_move;
    double target_lift = 0;
    {
@@ -851,7 +917,7 @@ std::string GCodeWriter::eager_lift(const LiftType type) {
    }

    // BBS: spiral lift only safe with known position
-    if (type == LiftType::SpiralLift && this->is_current_position_clear()) {
+    if (effective_type == LiftType::SpiralLift && this->is_current_position_clear()) {
        double radius = target_lift / (2 * PI * atan(filament()->travel_slope()));
        // static spiral alignment when no move in x,y plane.
        // spiral centra is a radius distance to the right (y=0)
@@ -868,7 +934,12 @@ std::string GCodeWriter::eager_lift(const LiftType type) {
    }
    //BBS: if position is unknown use normal lift
    else if (target_lift > 0) {
-        lift_move = _travel_to_z(m_pos(2) + target_lift, "normal lift Z");
+        if (this->must_skip_lift_now())
+            // Skipped, not deferred: leave m_lifted at zero below so unlift()
+            // does not descend from a height that was never commanded.
+            target_lift = 0.;
+        else
+            lift_move = _travel_to_z(m_pos(2) + target_lift, "normal lift Z");
    }
    m_lifted = target_lift;
    m_to_lift = 0;
@@ -889,7 +960,12 @@ std::string GCodeWriter::travel_to_xyz(const Vec3d &point, const std::string &co
        // BBS
    Vec3d dest_point = point;
    auto travel_speed =
-        m_is_first_layer ? this->config.get_abs_value_at("initial_layer_travel_speed", m_cached_extruder_idx) : this->config.travel_speed.get_at(m_cached_extruder_idx);
+        this->point_on_first_layer(Vec3d(point.x() - m_x_offset, point.y() - m_y_offset, point.z())) ? this->config.get_abs_value_at("initial_layer_travel_speed", m_cached_extruder_idx) : this->config.travel_speed.get_at(m_cached_extruder_idx);
+    // See uses_pointwise_travel_speed(): the historical path deliberately emits the
+    // raw configured speed in the final branch below, ignoring travel_speed.
+    const double final_travel_speed = this->uses_pointwise_travel_speed()
+        ? travel_speed
+        : this->config.travel_speed.get_at(m_cached_extruder_idx);
    //BBS: a z_hop need to be handle when travel
    if (std::abs(m_to_lift) > EPSILON) {
        assert(std::abs(m_lifted) < EPSILON);
@@ -938,13 +1014,23 @@ std::string GCodeWriter::travel_to_xyz(const Vec3d &point, const std::string &co
                Vec2d temp = delta_no_z.normalized() * delta(2) / tan(this->filament()->travel_slope());
                Vec3d slope_top_point = Vec3d(temp(0), temp(1), delta(2)) + source;
                GCodeG1Formatter w0;
-                w0.emit_xyz(slope_top_point);
+                // A slope lift is a straight (linear) diagonal move, so remapping its
+                // endpoint is exact. Route the destination through apply_axis_remap()
+                // when a remap is active (no-op at identity).
+                w0.emit_xyz(has_axis_remap() ? apply_axis_remap(slope_top_point) : slope_top_point);
                w0.emit_f(travel_speed * 60.0);
                //BBS
                w0.emit_comment(GCodeWriter::full_gcode_comment, comment);
                slop_move = w0.string();
            }
-            else if (m_to_lift_type == LiftType::NormalLift) {
+            else if (m_to_lift_type == LiftType::NormalLift && ! this->must_skip_lift_now()) {
+                // Only lift in place when the current position is known, for a mapping
+                // that makes _travel_to_z re-emit logical X/Y: at print start (and after
+                // custom gcode) m_pos.xy is still the uninitialised origin, which would
+                // map to a bogus machine point. The xy_z_move below then travels straight
+                // to the destination with full XYZ and establishes the correct position.
+                // Mappings that do not need this (the historical Cartesian behaviour)
+                // report false and keep lifting unconditionally.
                slop_move = _travel_to_z(target.z(), "normal lift Z");
            }
        }
@@ -952,7 +1038,14 @@ std::string GCodeWriter::travel_to_xyz(const Vec3d &point, const std::string &co
        std::string xy_z_move;
        {
            GCodeG1Formatter w0;
-            if (this->is_current_position_clear()) {
+            if (has_axis_remap()) {
+                // Remap may couple XY with Z; emit full XYZ in machine coordinates.
+                w0.emit_xyz(apply_axis_remap(target));
+                w0.emit_f(travel_speed * 60.0);
+                w0.emit_comment(GCodeWriter::full_gcode_comment, comment);
+                xy_z_move = w0.string();
+            }
+            else if (this->is_current_position_clear()) {
                w0.emit_xyz(target);
                w0.emit_f(travel_speed * 60.0);
                w0.emit_comment(GCodeWriter::full_gcode_comment, comment);
@@ -990,17 +1083,23 @@ std::string GCodeWriter::travel_to_xyz(const Vec3d &point, const std::string &co
    Vec3d point_on_plate = { dest_point(0) - m_x_offset, dest_point(1) - m_y_offset, dest_point(2) };
    std::string out_string;
    GCodeG1Formatter w;
-    if (!this->is_current_position_clear())
+    if (has_axis_remap()) {
+        // Remap may couple XY with Z; emit full XYZ in machine coordinates.
+        w.emit_xyz(apply_axis_remap(point_on_plate));
+        w.emit_f(final_travel_speed * 60.0);
+        w.emit_comment(GCodeWriter::full_gcode_comment, comment);
+        out_string = w.string();
+    } else if (!this->is_current_position_clear())
    {
        //force to move xy first then z after filament change
        w.emit_xy(Vec2d(point_on_plate.x(), point_on_plate.y()));
-        w.emit_f(this->config.travel_speed.get_at(m_cached_extruder_idx) * 60.0);
+        w.emit_f(final_travel_speed * 60.0);
        w.emit_comment(GCodeWriter::full_gcode_comment, comment);
        out_string = w.string() + _travel_to_z(point_on_plate.z(), comment);
    } else {
        GCodeG1Formatter w;
        w.emit_xyz(point_on_plate);
-        w.emit_f(this->config.travel_speed.get_at(m_cached_extruder_idx) * 60.0);
+        w.emit_f(final_travel_speed * 60.0);
        w.emit_comment(GCodeWriter::full_gcode_comment, comment);
        out_string = w.string();
    }
@@ -1035,12 +1134,19 @@ std::string GCodeWriter::_travel_to_z(double z, const std::string &comment)

    double speed = this->config.travel_speed_z.get_at(m_cached_extruder_idx);
    if (speed == 0.) {
-        speed = m_is_first_layer ? this->config.get_abs_value_at("initial_layer_travel_speed", m_cached_extruder_idx)
-                                 : this->config.travel_speed.get_at(m_cached_extruder_idx);
+        speed = this->point_on_first_layer(Vec3d(m_pos.x() - m_x_offset, m_pos.y() - m_y_offset, z))
+                    ? this->config.get_abs_value_at("initial_layer_travel_speed", m_cached_extruder_idx)
+                    : this->config.travel_speed.get_at(m_cached_extruder_idx);
    }

    GCodeG1Formatter w;
-    w.emit_z(z);
+    if (has_axis_remap()) {
+        // Remap may couple Z with other axes; emit full XYZ.
+        Vec3d machine = apply_axis_remap(Vec3d(m_pos.x() - m_x_offset, m_pos.y() - m_y_offset, z));
+        w.emit_xyz(machine);
+    } else {
+        w.emit_z(z);
+    }
    w.emit_f(speed * 60.0);
    //BBS
    w.emit_comment(GCodeWriter::full_gcode_comment, comment);
@@ -1049,6 +1155,14 @@ std::string GCodeWriter::_travel_to_z(double z, const std::string &comment)

 std::string GCodeWriter::_spiral_travel_to_z(double z, const Vec2d &ij_offset, const std::string &comment)
 {
+    // A circular XY arc / spiral lift cannot be correctly axis-remapped by
+    // transforming only its endpoint: the arc plane (G17/XY) and the I-J center
+    // would change under the remap. When an axis remap is active, fall back to a
+    // plain linear lift instead of emitting a possibly-wrong spiral/arc. This
+    // single guard covers every spiral call site (lazy/eager lift and travel_to_xyz).
+    if (has_axis_remap())
+        return _travel_to_z(z, comment);
+
    std::string output;
    double speed = this->config.travel_speed_z.get_at(m_cached_extruder_idx);

@@ -1155,7 +1269,12 @@ void GCodeWriter::extrude_to_xy(std::string &out, const Vec2d &point, double dE,
    Vec2d point_on_plate = { point(0) - m_x_offset, point(1) - m_y_offset };

    GCodeG1Formatter w;
-    w.emit_xy(point_on_plate);
+    if (has_axis_remap()) {
+        Vec3d machine = apply_axis_remap(Vec3d(point_on_plate.x(), point_on_plate.y(), m_pos.z()));
+        w.emit_xyz(machine);
+    } else {
+        w.emit_xy(point_on_plate);
+    }
    if (!force_no_extrusion)
        w.emit_e(filament()->E());
    //BBS
@@ -1163,6 +1282,42 @@ void GCodeWriter::extrude_to_xy(std::string &out, const Vec2d &point, double dE,
    w.append_to(out);
 }

+// Approximate an arc with linear extrusions, for machine mappings that cannot
+// express a G2/G3 (see extrude_arc_to_xy). center_offset is I/J: the centre
+// relative to the CURRENT position, which is why this must run before m_pos is
+// updated.
+void GCodeWriter::extrude_arc_as_polyline(std::string &out, const Vec2d &point, const Vec2d &center_offset,
+                                          double dE, const bool is_ccw,
+                                          const std::string &comment, bool force_no_extrusion)
+{
+    const Vec2d start  = Vec2d(m_pos.x(), m_pos.y());
+    const Vec2d centre = start + center_offset;
+    const double r     = (start - centre).norm();
+    if (r < EPSILON) {
+        // Degenerate: no arc to speak of, so a single move is exact.
+        this->extrude_to_xy(out, point, dE, comment, force_no_extrusion);
+        return;
+    }
+
+    double a0 = std::atan2(start.y() - centre.y(), start.x() - centre.x());
+    double a1 = std::atan2(point.y() - centre.y(), point.x() - centre.x());
+    double sweep = a1 - a0;
+    if (is_ccw) { while (sweep <= 0.) sweep += 2. * PI; }
+    else        { while (sweep >= 0.) sweep -= 2. * PI; }
+
+    // Segment count from a chord-deviation bound: r*(1-cos(dtheta/2)) <= tol.
+    const double tol  = 0.005;                       // mm
+    const double dmax = (tol >= r) ? PI : 2. * std::acos(1. - tol / r);
+    const int    n    = std::max(2, int(std::ceil(std::abs(sweep) / std::max(dmax, EPSILON))));
+
+    for (int i = 1; i <= n; ++ i) {
+        const double a = a0 + sweep * (double(i) / double(n));
+        const Vec2d  p = (i == n) ? point
+                                  : Vec2d(centre.x() + r * std::cos(a), centre.y() + r * std::sin(a));
+        this->extrude_to_xy(out, p, dE / double(n), i == n ? comment : std::string(), force_no_extrusion);
+    }
+}
+
 //BBS: generate G2 or G3 extrude which moves by arc
 //point is end point which means X and Y axis
 //center_offset is I and J axis
@@ -1175,6 +1330,23 @@ std::string GCodeWriter::extrude_arc_to_xy(const Vec2d& point, const Vec2d& cent

 void GCodeWriter::extrude_arc_to_xy(std::string &out, const Vec2d& point, const Vec2d& center_offset, double dE, const bool is_ccw, const std::string& comment, bool force_no_extrusion)
 {
+    // Arcs emit only X/Y/I/J, so a mapping that moves logical X or Y cannot be
+    // expressed as a G2/G3. GCode::should_disable_arc_fitting() normally stops
+    // arcs being generated at all for such a mapping, but this is public API, so
+    // define the behaviour rather than asserting.
+    //
+    // This check MUST precede every state mutation below: falling through to
+    // extrude_to_xy() after filament()->extrude(dE) would advance E twice.
+    //
+    // A single chord is not a safe substitute either -- a semicircle would become
+    // its diameter and a full circle a stationary blob -- so approximate the arc
+    // with linear segments bounded by a chord tolerance, splitting dE between
+    // them in proportion to arc length.
+    if (! m_kinematics->supports_arc_moves()) {
+        this->extrude_arc_as_polyline(out, point, center_offset, dE, is_ccw, comment, force_no_extrusion);
+        return;
+    }
+
    m_pos(0) = point(0);
    m_pos(1) = point(1);
    if (!force_no_extrusion)
@@ -1215,10 +1387,18 @@ void GCodeWriter::extrude_to_xyz(std::string &out, const Vec3d &point, double dE
    Vec3d point_on_plate = { point(0) - m_x_offset, point(1) - m_y_offset, point(2) };

    GCodeG1Formatter w;
-    if (z_changed)
+    if (has_axis_remap()) {
+        // z_changed was computed from the ORIGINAL slicing Z, but an axis remap can
+        // make machine-Z depend on slicing X/Y. An X/Y-only move (slicing-Z
+        // unchanged) would then drop the required machine-Z word, so always emit
+        // full XYZ whenever a remap is active.
+        point_on_plate = apply_axis_remap(point_on_plate);
        w.emit_xyz(point_on_plate);
-    else
+    } else if (z_changed) {
+        w.emit_xyz(point_on_plate);
+    } else {
        w.emit_xy(Vec2d(point_on_plate.x(), point_on_plate.y()));
+    }
    if (!force_no_extrusion)
        w.emit_e(filament()->E());
    //BBS
@@ -10,31 +10,38 @@
 #include <string>
 #include <charconv>
 #include <vector>
+#include <functional>
+#include <utility>
 #include "Extruder.hpp"
 #include "Point.hpp"
 #include "Polygon.hpp"
 #include "PrintConfig.hpp"
 #include "Config.hpp"
+#include "GCode/MachineKinematics.hpp"
+#include <memory>

 namespace Slic3r {

+
 class GCodeWriter {
 public:
    GCodeConfig config;
    bool multiple_extruders;

    GCodeWriter() :
-        multiple_extruders(false), m_curr_filament_extruder(MAXIMUM_EXTRUDER_NUMBER, nullptr),
-        m_curr_extruder_id (-1),
-        m_cached_extruder_idx(0),
-        m_single_extruder_multi_material(false),
-        m_last_acceleration(0), m_max_acceleration(0),m_last_travel_acceleration(0), m_max_travel_acceleration(0),
-        m_last_jerk(0), m_max_jerk_x(0), m_max_jerk_y(0),
-        m_last_bed_temperature(0), m_last_bed_temperature_reached(true),
+        multiple_extruders(false),
        m_lifted(0),
        m_to_lift(0),
        m_to_lift_type(LiftType::NormalLift),
-        m_current_speed(3600), m_is_first_layer(true)
+        m_is_first_layer(true), m_current_speed(3600),
+        m_kinematics(std::make_unique<CartesianKinematics>()),
+        m_cached_extruder_idx(0),
+        m_curr_filament_extruder(MAXIMUM_EXTRUDER_NUMBER, nullptr),
+        m_curr_extruder_id (-1),
+        m_single_extruder_multi_material(false),
+        m_last_acceleration(0), m_max_acceleration(0),m_last_travel_acceleration(0), m_max_travel_acceleration(0),
+        m_last_jerk(0), m_max_jerk_x(0), m_max_jerk_y(0),
+        m_last_bed_temperature(0), m_last_bed_temperature_reached(true)
        {}
    Extruder* filament(size_t extruder_id) { assert(extruder_id < m_curr_filament_extruder.size()); return m_curr_filament_extruder[extruder_id]; }
    const Extruder* filament(size_t extruder_id) const { assert(extruder_id < m_curr_filament_extruder.size()); return m_curr_filament_extruder[extruder_id]; }
@@ -91,6 +98,10 @@ public:
    std::string extrude_to_xy(const Vec2d &point, double dE, const std::string &comment = std::string(), bool force_no_extrusion = false);
    //BBS: generate G2 or G3 extrude which moves by arc
    std::string extrude_arc_to_xy(const Vec2d &point, const Vec2d &center_offset, double dE, const bool is_ccw, const std::string &comment = std::string(), bool force_no_extrusion = false);
+    // Linear approximation of an arc, used when the machine mapping cannot
+    // express a G2/G3. Must be called before m_pos is updated: center_offset is
+    // relative to the current position.
+    void        extrude_arc_as_polyline(std::string &out, const Vec2d &point, const Vec2d &center_offset, double dE, const bool is_ccw, const std::string &comment = std::string(), bool force_no_extrusion = false);
    std::string extrude_to_xyz(const Vec3d &point, double dE, const std::string &comment = std::string(), bool force_no_extrusion = false);
    // Each appends its line to `out`.
    void        set_speed(std::string &out, double F, const std::string &comment = std::string(), const std::string &cooling_marker = std::string());
@@ -147,16 +158,94 @@ public:
    void invalidate_acceleration() { m_last_acceleration = 0; m_last_travel_acceleration = 0; }
    void invalidate_jerk() { m_last_jerk = 0; }

+    // Axis remap: permute/negate/reverse axes in G-code output.
+    // Works standalone (without belt mode) for printers with non-standard axis conventions.
+    void set_axis_remap(int rx, int ry, int rz);
+    void set_build_volume_max(const Vec3d &max);
+    bool has_axis_remap() const;
+
+    // Install the machine frame mapping.  Any axis remap / build volume already
+    // configured is carried over, so install order does not matter.
+    void set_kinematics(std::unique_ptr<MachineKinematics> kinematics);
+    const MachineKinematics& kinematics() const { return *m_kinematics; }
+
+    // Per-point first-layer test.  When set, travel speed selection asks it per
+    // destination point (in the writer's logical placed frame) instead of using
+    // the layer-coarse m_is_first_layer flag.  GCode installs it on belt printers
+    // with the same test its extrusions use (GCode::on_first_layer(point)), so a
+    // travel is judged against the belt surface exactly as the path it leads to.
+    using FirstLayerPointTest = std::function<bool(const Vec3d &point_logical)>;
+    void set_first_layer_point_test(FirstLayerPointTest test) { m_first_layer_point_test = std::move(test); }
+
+    // Force every lift to a plain vertical lift.  Spiral and slope lifts compute
+    // their slope in the logical frame and do not account for a machine mapping
+    // that couples axes.
+    void set_force_normal_lift(bool force) { m_force_normal_lift = force; }
+
    // Returns whether this flavor supports separate print and travel acceleration.
    static bool supports_separate_travel_acceleration(GCodeFlavor flavor);
-  private:
+protected:
+    // Position/lift/offset state.
+    Vec3d           m_pos = Vec3d::Zero();
+    double          m_x_offset{ 0 };
+    double          m_y_offset{ 0 };
+    double          m_lifted;
+    double          m_to_lift;
+    LiftType        m_to_lift_type;
+    bool            m_is_first_layer = true;
+    bool            m_is_current_pos_clear = false;
+    double          m_current_speed;
+
+    std::string _travel_to_z(double z, const std::string &comment);
+
+    // Whether a destination gets first-layer treatment.  With a point test
+    // installed it decides; otherwise the layer-coarse m_is_first_layer flag does.
+    bool point_on_first_layer(const Vec3d &point_logical) const;
+
+    // True when a lift must be skipped because this mapping would emit the
+    // stored logical X/Y and that position is not yet known.
+    bool must_skip_lift_now() const;
+
+    // True when travel speed is selected per destination point rather than per
+    // layer. Set for writers that install a first-layer point test. The
+    // historical path emits the raw configured travel speed in the final branch
+    // of travel_to_xyz(), ignoring the first-layer selection computed at the top
+    // of that function; a point-test-driven writer uses the first-layer-aware
+    // value throughout. Both are preserved exactly -- unifying them would change
+    // emitted feedrates and belongs in its own commit.
+    bool uses_pointwise_travel_speed() const { return bool(m_first_layer_point_test); }
+
+    FirstLayerPointTest    m_first_layer_point_test;
+    bool                   m_force_normal_lift = false;
+
+    // The machine frame mapping.  Owns the axis-remap state that used to live
+    // here as m_remap_* / m_build_vol_max; the setters above forward to it.
+    // Never null: a CartesianKinematics at the identity remap reproduces the
+    // historical behaviour exactly.
+    std::unique_ptr<MachineKinematics> m_kinematics;
+
+    // Last configured remap / build volume, replayed onto a newly installed
+    // kinematics so set_kinematics() and the setters are order-independent.
+    int             m_remap_x = 0;  // RemapAxis: 0=+X, 1=+Y, 2=+Z, 3=-X, etc.
+    int             m_remap_y = 1;
+    int             m_remap_z = 2;
+    Vec3d           m_build_vol_max = Vec3d::Zero();
+
+    // Apply the machine frame mapping to a point. Returns pos unchanged when the
+    // mapping is the identity.
+    Vec3d apply_axis_remap(const Vec3d &pos) const;
+
+    // Motion uses the global/base process variant until a filament becomes active.
+    // Protected so subclasses index the per-extruder speed options (travel_speed,
+    // travel_speed_z, initial_layer_travel_speed) exactly as the base writer does.
+    size_t     m_cached_extruder_idx;
+
+private:
 	// Extruders are sorted by their ID, so that binary search is possible.
    std::vector<Extruder> m_filament_extruders;
    bool            m_single_extruder_multi_material;
    std::vector<Extruder*> m_curr_filament_extruder;
    int        m_curr_extruder_id;
-    // Motion uses the global/base process variant until a filament becomes active.
-    size_t     m_cached_extruder_idx;
    unsigned int              m_last_acceleration;
    unsigned int              m_last_travel_acceleration;
    std::vector<unsigned int> m_max_travel_acceleration;
@@ -178,19 +267,6 @@ public:
    //BBS
    int             m_last_bed_temperature;
    bool            m_last_bed_temperature_reached;
-    double          m_lifted;
-
-    // BBS
-    double          m_to_lift;
-    LiftType        m_to_lift_type;
-    Vec3d           m_pos = Vec3d::Zero();
-    //BBS: this flag is used to indicate whether the m_pos is real.
-    //A example that of the first move, the m_pos is zero, but the real position of extruder doesn't
-    //Pos must be clear after the first xyz travel move
-    bool            m_is_current_pos_clear = false;
-    //BBS: x, y offset for gcode generated
-    double          m_x_offset{ 0 };
-    double          m_y_offset{ 0 };

    // Orca: slicing resolution in mm
    double          m_resolution = 0.01;
@@ -202,21 +278,18 @@ public:
    // non-rectangular beds such as delta/circular printers.
    Polygon              m_bed_printable_area;
    std::vector<Polygon> m_extruder_printable_areas;
-    
+
    std::string m_gcode_label_objects_start;
    std::string m_gcode_label_objects_end;

    //SoftFever
    bool            m_is_bbl_printers = false;
-    double          m_current_speed;
-    bool            m_is_first_layer = true;

    enum class Acceleration {
        Travel,
        Print
    };

-    std::string _travel_to_z(double z, const std::string &comment);
    std::string _spiral_travel_to_z(double z, const Vec2d &ij_offset, const std::string &comment);
    // Orca: printable area of the active extruder (per-extruder when configured, otherwise the bed). Null when unknown.
    const Polygon *active_printable_area() const;
@@ -1259,7 +1259,7 @@ static inline std::vector<std::vector<ExPolygons>> segmentation_top_and_bottom_l
    // project downards pointing painted triangles over bottom surfaces.
    std::vector<std::vector<Polygons>> top_raw(num_facets_states), bottom_raw(num_facets_states);
    std::vector<float> zs = zs_from_layers(layers);
-    Transform3d        object_trafo = print_object.trafo_centered();
+    Transform3d        object_trafo = print_object.trafo_sliced();

 #ifdef MM_SEGMENTATION_DEBUG_TOP_BOTTOM
    static int iRun = 0;
@@ -1288,10 +1288,16 @@ static inline std::vector<std::vector<ExPolygons>> segmentation_top_and_bottom_l
                            slicing_params.trafo = volume_trafo;
                            Polygons bottom_slice = slice_mesh(painted, zs[0], slicing_params);

-                            top.erase(top.begin());
-                            bottom.erase(bottom.begin());
-
-                            bottom[0] = union_(bottom[0], bottom_slice);
+                            // Only the requested projections exist: with
+                            // top_shell_layers = 0 `top` is empty and erasing its begin() was
+                            // undefined (found by fuzzing: a sunk, painted object crashed here).
+                            if (! top.empty())
+                                top.erase(top.begin());
+                            if (! bottom.empty()) {
+                                bottom.erase(bottom.begin());
+                                if (! bottom.empty())
+                                    bottom[0] = union_(bottom[0], bottom_slice);
+                            }
                        } else
                            slice_mesh_slabs(painted, zs, volume_trafo, max_top_layers > 0 ? &top : nullptr, max_bottom_layers > 0 ? &bottom : nullptr, nullptr, throw_on_cancel_callback);
                        auto merge = [](std::vector<Polygons> &&src, std::vector<Polygons> &dst) {
@@ -2087,17 +2093,19 @@ std::vector<std::vector<ExPolygons>> segmentation_by_painting(const PrintObject
    }

    BOOST_LOG_TRIVIAL(debug) << "Print object segmentation - Projection of painted triangles - Begin";
+    // The layers were sliced in this frame (belt rotation, remap and Z lift included), and it already centers the object.
+    const Transform3d object_trafo = print_object.trafo_sliced();
    for (const ModelVolume *mv : print_object.model_object()->volumes) {
        const ModelVolumeFacetsInfo facets_info = extract_facets_info(*mv);
-        tbb::parallel_for(tbb::blocked_range<size_t>(1, num_facets_states), [&mv, &print_object, &facets_info, &layers, &edge_grids, &painted_lines, &painted_lines_mutex, &input_expolygons, &throw_on_cancel_callback](const tbb::blocked_range<size_t> &range) {
+        tbb::parallel_for(tbb::blocked_range<size_t>(1, num_facets_states), [&mv, &object_trafo, &facets_info, &layers, &edge_grids, &painted_lines, &painted_lines_mutex, &input_expolygons, &throw_on_cancel_callback](const tbb::blocked_range<size_t> &range) {
            for (size_t extruder_idx = range.begin(); extruder_idx < range.end(); ++extruder_idx) {
                throw_on_cancel_callback();
                const indexed_triangle_set custom_facets = facets_info.facets_annotation.get_facets(*mv, EnforcerBlockerType(extruder_idx));
                if (!mv->is_model_part() || custom_facets.indices.empty())
                    continue;

-                const Transform3f tr = print_object.trafo().cast<float>() * mv->get_matrix().cast<float>();
-                tbb::parallel_for(tbb::blocked_range<size_t>(0, custom_facets.indices.size()), [&tr, &custom_facets, &print_object, &layers, &edge_grids, &input_expolygons, &painted_lines, &painted_lines_mutex, &extruder_idx](const tbb::blocked_range<size_t> &range) {
+                const Transform3f tr = (object_trafo * mv->get_matrix()).cast<float>();
+                tbb::parallel_for(tbb::blocked_range<size_t>(0, custom_facets.indices.size()), [&tr, &custom_facets, &layers, &edge_grids, &input_expolygons, &painted_lines, &painted_lines_mutex, &extruder_idx](const tbb::blocked_range<size_t> &range) {
                    for (size_t facet_idx = range.begin(); facet_idx < range.end(); ++facet_idx) {
                        float min_z = std::numeric_limits<float>::max();
                        float max_z = std::numeric_limits<float>::lowest();
@@ -2150,7 +2158,6 @@ std::vector<std::vector<ExPolygons>> segmentation_by_painting(const PrintObject

                            Line line_to_test(Point(scale_(line_start_f.x()), scale_(line_start_f.y())),
                                              Point(scale_(line_end_f.x()), scale_(line_end_f.y())));
-                            line_to_test.translate(-print_object.center_offset());

                            // BoundingBoxes for EdgeGrids are computed from printable regions. It is possible that the painted line (line_to_test) could
                            // be outside EdgeGrid's BoundingBox, for example, when the negative volume is used on the painted area (GH #7618).
@@ -759,59 +759,6 @@ static void clip_inner_walls_over_top(std::vector<Arachne::VariableWidthLines> &
    }
 }

-// ORCA: only_one_wall_top - widest bead of the given walls.
-static coord_t widest_bead(const std::vector<Arachne::VariableWidthLines> &walls)
-{
-    coord_t widest = 0;
-    for (const Arachne::VariableWidthLines &group : walls)
-        for (const Arachne::ExtrusionLine &el : group)
-            for (const Arachne::ExtrusionJunction &j : el.junctions)
-                widest = std::max(widest, j.w);
-    return widest;
-}
-
-// ORCA: only_one_wall_top - length of the walls running further than tolerance from the reference walls, outside the
-// excluded area.
-static double length_off_reference(const std::vector<Arachne::VariableWidthLines> &walls, const Arachne::VariableWidthLines &reference,
-                                   const ExPolygons &excluded, coord_t tolerance)
-{
-    auto append_centerlines = [](const Arachne::VariableWidthLines &lines, Polylines &out) {
-        for (const Arachne::ExtrusionLine &el : lines) {
-            if (el.junctions.size() < 2)
-                continue;
-            Polyline &centerline = out.emplace_back();
-            centerline.points.reserve(el.junctions.size());
-            for (const Arachne::ExtrusionJunction &j : el.junctions)
-                centerline.points.emplace_back(j.p);
-        }
-    };
-    Polylines wall_centerlines;
-    Polylines reference_centerlines;
-    for (const Arachne::VariableWidthLines &group : walls)
-        append_centerlines(group, wall_centerlines);
-    append_centerlines(reference, reference_centerlines);
-
-    Polylines off_reference = diff_pl(wall_centerlines, offset(reference_centerlines, float(tolerance)));
-    if (! excluded.empty())
-        off_reference = diff_pl(off_reference, excluded);
-    return total_length(off_reference);
-}
-
-// ORCA: only_one_wall_top - area covered by the given walls at their local widths.
-static Polygons walls_footprint(const Arachne::VariableWidthLines &walls)
-{
-    Polygons footprint;
-    for (const Arachne::ExtrusionLine &el : walls)
-        for (size_t i = 1; i < el.junctions.size(); ++ i) {
-            const Arachne::ExtrusionJunction &a     = el.junctions[i - 1];
-            const Arachne::ExtrusionJunction &b     = el.junctions[i];
-            const coord_t                     width = std::max(a.w, b.w);
-            if (width > 0)
-                append(footprint, offset(Polyline(a.p, b.p), float(width) / 2.f));
-        }
-    return union_(footprint);
-}
-
 void PerimeterGenerator::split_top_surfaces(const ExPolygons &orig_polygons, ExPolygons &top_fills,
                                            ExPolygons &non_top_polygons, ExPolygons &fill_clip) const {
    // other perimeters
@@ -2599,90 +2546,44 @@ void PerimeterGenerator::process_arachne()
        if (inner_loop_number >= 0) {
            assert(upper_slices != nullptr);

+            // Infill contour bounding box.
+            BoundingBox infill_contour_bbox = get_extents(infill_contour);
+            infill_contour_bbox.offset(SCALED_EPSILON);
+            
            coord_t perimeter_width = this->perimeter_flow.scaled_width();

-            // Filter out areas that are too thin and expand top surface polygons a bit to hide the wall line.
-            // ORCA: skip if the top surface area is smaller than "min_width_top_surface"
-            const float top_surface_min_width = std::max<float>(float(ext_perimeter_spacing) / 4.f + scaled<float>(0.00001), float(scale_(config->min_width_top_surface.get_abs_value(unscale_(perimeter_width)))) / 4.f);
+            // Get top ExPolygons from current infill contour.
+            Polygons upper_slices_clipped;
+            if (object_config->interface_shells) {
+                auto upper_slicer_same_region = to_expolygons(this->upper_slices_same_region->surfaces);
+                upper_slices_clipped = ClipperUtils::clip_clipper_polygons_with_subject_bbox(upper_slicer_same_region, infill_contour_bbox);
+            } else
+                upper_slices_clipped = ClipperUtils::clip_clipper_polygons_with_subject_bbox(*upper_slices, infill_contour_bbox);

-            // Get top ExPolygons from the given contour. uncovered reports whether the upper layer leaves any of the
-            // contour uncovered, before bridges and too thin areas are filtered out.
-            auto get_top_expolygons = [&](const ExPolygons &contour, bool &uncovered) {
-                // Contour bounding box.
-                BoundingBox contour_bbox = get_extents(contour);
-                contour_bbox.offset(SCALED_EPSILON);
-
-                Polygons upper_slices_clipped;
-                if (object_config->interface_shells) {
-                    auto upper_slicer_same_region = to_expolygons(this->upper_slices_same_region->surfaces);
-                    upper_slices_clipped = ClipperUtils::clip_clipper_polygons_with_subject_bbox(upper_slicer_same_region, contour_bbox);
-                } else
-                    upper_slices_clipped = ClipperUtils::clip_clipper_polygons_with_subject_bbox(*upper_slices, contour_bbox);
-
-                ExPolygons top = diff_ex(contour, upper_slices_clipped);
-                uncovered      = !top.empty();
-                if (top.empty())
-                    return top;
+            top_expolygons = diff_ex(infill_contour, upper_slices_clipped);

+            if (!top_expolygons.empty()) {
                if (lower_slices != nullptr) {
                    const float      bridge_offset          = float(std::max<coord_t>(ext_perimeter_spacing, perimeter_width));
-                    const Polygons   lower_slices_clipped   = ClipperUtils::clip_clipper_polygons_with_subject_bbox(*lower_slices, contour_bbox);
-                    const ExPolygons current_slices_bridges = offset_ex(diff_ex(top, lower_slices_clipped), bridge_offset);
+                    const Polygons   lower_slices_clipped   = ClipperUtils::clip_clipper_polygons_with_subject_bbox(*lower_slices, infill_contour_bbox);
+                    const ExPolygons current_slices_bridges = offset_ex(diff_ex(top_expolygons, lower_slices_clipped), bridge_offset);

                    // Remove bridges from top surface polygons.
-                    top = diff_ex(top, current_slices_bridges);
+                    top_expolygons = diff_ex(top_expolygons, current_slices_bridges);
                }

+                // Filter out areas that are too thin and expand top surface polygons a bit to hide the wall line.
+                // ORCA: skip if the top surface area is smaller than "min_width_top_surface"
+                const float top_surface_min_width = std::max<float>(float(ext_perimeter_spacing) / 4.f + scaled<float>(0.00001), float(scale_(config->min_width_top_surface.get_abs_value(unscale_(perimeter_width)))) / 4.f);
                // Shrink the polygon to remove the small areas, then expand it back out plus a maragin to hide the wall line a little.
                // ORCA: Expand the polygon with half the perimeter width in addition to the contracted amount,
                // not the full perimeter width as PS does, to enable thin lettering to print on the top surface without nozzle collisions
                // due to thin lines being generated
-                top = offset2_ex(top, -top_surface_min_width, top_surface_min_width + float(perimeter_width * 0.85));
+                top_expolygons = offset2_ex(top_expolygons, -top_surface_min_width, top_surface_min_width + float(perimeter_width * 0.85));

                // Get final top ExPolygons (bridges were excluded above, so they stay walled).
-                return intersection_ex(top, contour);
-            };
+                top_expolygons = intersection_ex(top_expolygons, infill_contour);

-            // Walls with the full count, as generated when the single perimeter feature is disabled. Generated on first use.
-            std::vector<Arachne::VariableWidthLines> full_perimeters;
-            Polygons                                 full_inner_contour;
-            bool                                     full_perimeters_generated = false;
-            auto generate_full_perimeters = [&]() {
-                if (full_perimeters_generated)
-                    return;
-                Arachne::WallToolPaths full_tool_paths(last_p, bead_width_0, perimeter_spacing, coord_t(inner_loop_number + 2), wall_0_inset, layer_height, input_params_tmp);
-                full_perimeters           = full_tool_paths.getToolPaths();
-                full_inner_contour        = full_tool_paths.getInnerContour();
-                full_perimeters_generated = true;
-            };
-
-            // ORCA: the single wall pass allows Arachne 2 beads across a wall, so it fills a wall narrower than 3 outer wall
-            // widths by widening both, where the full pass adds a middle bead. Over the top surface that is the intent;
-            // anywhere else it leaves no room for the inner walls. When the single wall pass's outer walls run away from
-            // the full pass's outside the top surface, take the full pass's outer walls and the area inside them instead.
-            // Walls closer than outer_wall_tolerance count as the same wall: a widened bead's centerline moves by half
-            // the width added, and only beads widened by more than twice the tolerance are looked for.
-            const coord_t outer_wall_tolerance = bead_width_0 / 10;
-            if (widest_bead(perimeters) > bead_width_0 + 2 * outer_wall_tolerance) {
-                // The single wall pass's inner contour where it widens no bead: inside nominal width outer walls.
-                const ExPolygons nominal_infill_contour = offset_ex(last, -float(bead_width_0 + wall_0_inset));
-                bool             nominal_uncovered      = false;
-                // Grown by an outer wall width to take in the outer walls bordering the top surface.
-                const ExPolygons top_zone = offset_ex(get_top_expolygons(nominal_infill_contour, nominal_uncovered), float(bead_width_0));
-                if (nominal_uncovered) {
-                    generate_full_perimeters();
-                    if (! full_perimeters.empty() && ! full_perimeters.front().empty() &&
-                        length_off_reference(perimeters, full_perimeters.front(), top_zone, outer_wall_tolerance) > double(perimeter_width)) {
-                        perimeters     = { full_perimeters.front() };
-                        infill_contour = diff_ex(nominal_infill_contour, walls_footprint(full_perimeters.front()), ApplySafetyOffset::Yes);
-                    }
-                }
-            }
-
-            bool uncovered = false;
-            top_expolygons = get_top_expolygons(infill_contour, uncovered);
-
-            if (uncovered) {
                // ORCA: onion the real region (inside the outer wall) so the remaining walls follow the actual
                // geometry, then cut away the parts over the top surface. Re-onioning the non-top complement
                // instead - the fallback when there is no top fill - walls the top/non-top interface and rings
@@ -2711,11 +2612,11 @@ void PerimeterGenerator::process_arachne()
                perimeters.insert(perimeters.end(), inner_perimeters.begin(), inner_perimeters.end());
                infill_contour = union_ex(top_expolygons, inner_wall_tool_paths.getInnerContour());
            } else {
-                // There is no top surface ExPolygon, so use the walls generated like when the single perimeter
-                // feature is disabled.
-                generate_full_perimeters();
-                perimeters     = std::move(full_perimeters);
-                infill_contour = union_ex(full_inner_contour);
+                // There is no top surface ExPolygon, so we call Arachne again with parameters
+                // like when the single perimeter feature is disabled.
+                Arachne::WallToolPaths no_single_perimeter_tool_paths(last_p, bead_width_0, perimeter_spacing, coord_t(inner_loop_number + 2), wall_0_inset, layer_height, input_params_tmp);
+                perimeters     = no_single_perimeter_tool_paths.getToolPaths();
+                infill_contour = union_ex(no_single_perimeter_tool_paths.getInnerContour());
            }
        }
        //PS
--- a/Show More
+++ b/Show More