delete mesh transforms (#37)

* delete mesh shear, scale and refactor logger

* clean up config options

* reorder UI elements

resources/profiles/Custom/machine/fdm_belt_common.json

@@ -82,9 +82,9 @@
 	"z_hop_types": [
 		"Normal Lift"
 	],
-	"post_gcode_remap_x": "rev_x",
+	"gcode_remap_x": "rev_x",
-	"post_gcode_remap_y": "pos_z",
+	"gcode_remap_y": "pos_z",
-	"post_gcode_remap_z": "pos_y",
+	"gcode_remap_z": "pos_y",
 	"printer_extruder_id": [
 		"1"
 	],
@@ -94,7 +94,6 @@
 	"belt_slice_rotation_global": "1",
 	"gcode_shear_z": "pos_tan",
 	"gcode_scale_y": "inv_cos",
-	"build_plate_tilt_x": "45",
 	"purge_in_prime_tower": "0",
 	"scan_first_layer": "0",
 	"auxiliary_fan": "0"

src/libslic3r/BeltGCode.cpp

@@ -14,7 +14,6 @@ void BeltGCode::init_belt_writer(Print &print, bool is_bbl_printers)
 
     auto belt_writer = std::make_unique<BeltGCodeWriter>();
     belt_writer->set_is_bbl_machine(is_bbl_printers);
-    belt_writer->set_belt_angle(print.config().belt_printer_angle.value);
     // Axis remap and build volume max are set by base GCode after init_belt_writer returns.
     belt_writer->set_belt_back_transform(print.config());
     belt_writer->set_machine_frame_transform(print.config());
@@ -34,30 +33,12 @@ void BeltGCode::write_belt_header(GCodeOutputStream &file, const Print &print)
     if (!print.config().belt_printer.value)
         return;
 
-    file.write_format("; belt_printer_angle = %.1f\n", print.config().belt_printer_angle.value);
-    // Shear configs
     const auto &full_cfg = print.full_print_config();
-    file.write_format("; belt_shear_x = %s\n",       full_cfg.opt_serialize("belt_shear_x").c_str());
+    // Slicing rotation: the belt tilt (axis + angle) and the single source of truth
-    file.write_format("; belt_shear_x_angle = %.1f\n", print.config().belt_shear_x_angle.value);
+    // for the physical tilt the G-code viewer uses to enable belt view.
-    file.write_format("; belt_shear_x_from = %s\n",  full_cfg.opt_serialize("belt_shear_x_from").c_str());
-    file.write_format("; belt_shear_y = %s\n",       full_cfg.opt_serialize("belt_shear_y").c_str());
-    file.write_format("; belt_shear_y_angle = %.1f\n", print.config().belt_shear_y_angle.value);
-    file.write_format("; belt_shear_y_from = %s\n",  full_cfg.opt_serialize("belt_shear_y_from").c_str());
-    file.write_format("; belt_shear_z = %s\n",       full_cfg.opt_serialize("belt_shear_z").c_str());
-    file.write_format("; belt_shear_z_angle = %.1f\n", print.config().belt_shear_z_angle.value);
-    file.write_format("; belt_shear_z_from = %s\n",  full_cfg.opt_serialize("belt_shear_z_from").c_str());
-    // Scale configs
-    file.write_format("; belt_scale_x = %s\n",       full_cfg.opt_serialize("belt_scale_x").c_str());
-    file.write_format("; belt_scale_x_angle = %.1f\n", print.config().belt_scale_x_angle.value);
-    file.write_format("; belt_scale_y = %s\n",       full_cfg.opt_serialize("belt_scale_y").c_str());
-    file.write_format("; belt_scale_y_angle = %.1f\n", print.config().belt_scale_y_angle.value);
-    file.write_format("; belt_scale_z = %s\n",       full_cfg.opt_serialize("belt_scale_z").c_str());
-    file.write_format("; belt_scale_z_angle = %.1f\n", print.config().belt_scale_z_angle.value);
-    // Slicing rotation configs
     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);
-    file.write_format("; belt_mesh_transform_order = %s\n", full_cfg.opt_serialize("belt_mesh_transform_order").c_str());
     // 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());
@@ -81,9 +62,6 @@ void BeltGCode::write_belt_header(GCodeOutputStream &file, const Print &print)
     file.write_format("; gcode_scale_z = %s\n",       full_cfg.opt_serialize("gcode_scale_z").c_str());
     file.write_format("; gcode_scale_z_angle = %.1f\n", print.config().gcode_scale_z_angle.value);
     file.write_format("; belt_gcode_transform_order = %s\n", full_cfg.opt_serialize("belt_gcode_transform_order").c_str());
-    file.write_format("; post_gcode_remap_x = %s\n",  full_cfg.opt_serialize("post_gcode_remap_x").c_str());
-    file.write_format("; post_gcode_remap_y = %s\n",  full_cfg.opt_serialize("post_gcode_remap_y").c_str());
-    file.write_format("; post_gcode_remap_z = %s\n",  full_cfg.opt_serialize("post_gcode_remap_z").c_str());
 }
 
 void BeltGCode::on_set_origin(const PrintObject *obj, const Point &inst_shift)
@@ -94,21 +72,16 @@ void BeltGCode::on_set_origin(const PrintObject *obj, const Point &inst_shift)
     // This replaces the bbox-based axis snap with an exact formula.
     //
     // Flags that trigger this path:
-    //   belt_preslice_global   — full pipeline (scale * shear * remap) is global
+    //   belt_preslice_global         — full pipeline (rotation * remap) is global
-    //   preslice_remap_global  — only the pre-slice remap is global
+    //   preslice_remap_global        — only the pre-slice remap is global
-    //   belt_shear_z_global    — Z-row shear treated as global (matches per-axis
+    //   belt_slice_rotation_global   — slicing rotation treated as global (matches
-    //                            Z-offset added in PrintObjectSlice.cpp)
+    //                                  the per-instance Z-offset added in PrintObjectSlice.cpp)
     // The XY origin adjustment uses the FULL forward transform either way,
     // because the back_transform applied during G-code emission is always the
-    // inverse of the full pipeline. Without pre-multiplication under
+    // inverse of the full pipeline.
-    // ShearThenScale order with sy != 1, machine_y of bed position cy ends up
-    // at cy/sy instead of cy, which also leaves the object bottom off the belt
-    // plane.
     bool use_global = m_config.belt_preslice_global.value
         || (m_config.preslice_remap_global.value
             && BeltTransformPipeline::has_preslice_remap(m_config))
-        || (m_config.belt_shear_z_global.value
-            && m_config.belt_shear_z.value != BeltShearMode::None)
         || (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);
@@ -117,10 +90,10 @@ void BeltGCode::on_set_origin(const PrintObject *obj, const Point &inst_shift)
         if (belt_writer) {
             // The per-object lift (z_shift_val = max(0, -m_belt_min_z)) added by
             // BeltSliceStrategy::apply_to_trafo is already compensated inside
-            // global_z_offset (via the shear_min_z term in PrintObjectSlice.cpp's
+            // global_z_offset (via the belt_z_shift term in PrintObjectSlice.cpp).
-            // preslice_global branch).  Snap was previously used here for the same
+            // Snap was previously used here for the same purpose, but with both
-            // purpose, but with both active the lift gets subtracted twice.  Clear
+            // active the lift gets subtracted twice.  Clear any leftover snap
-            // any leftover snap state from a prior instance.
+            // state from a prior instance.
             for (int a = 0; a < 3; ++a)
                 belt_writer->set_origin_snap(a, false, 0., 0.);
         }

src/libslic3r/BeltGCodeWriter.cpp

@@ -25,11 +25,6 @@ inline bool belt_point_on_first_layer(
 
 // ---- Belt configuration ---------------------------------------------------
 
-void BeltGCodeWriter::set_belt_angle(double angle_deg)
-{
-    m_belt_angle_rad = Geometry::deg2rad(angle_deg);
-}
-
 void BeltGCodeWriter::set_belt_back_transform(const PrintConfig &config)
 {
     m_belt_back_transform.init_from_config(config);
@@ -66,7 +61,7 @@ Vec3d BeltGCodeWriter::to_machine_coords(const Vec3d &pos) const
         if (m_origin_snap[i])
             result[i] -= (m_origin_bbox_min[i] - m_origin_offset[i]);
     Vec3d after_snap = result;
-    // Step 4: Machine-frame transform (gcode_shear / gcode_scale / post_gcode_remap)
+    // Step 4: Machine-frame transform (gcode_shear / gcode_scale)
     // applied LAST so it acts as a global linear transform on the placed coords.
     // Order matters: putting it before origin_snap would feed sheared bbox corners
     // into the snap's per-object min calculation, mis-normalizing non-cubic geometries

src/libslic3r/BeltGCodeWriter.hpp

@@ -19,8 +19,6 @@ public:
     BeltGCodeWriter() : GCodeWriter() {}
 
     // Belt configuration (axis remap is inherited from GCodeWriter)
-    void set_belt_angle(double angle_deg);
-    bool is_belt_printer() const { return m_belt_angle_rad != 0.; }
     void set_belt_back_transform(const PrintConfig &config);
     void set_machine_frame_transform(const PrintConfig &config);
     void set_origin_snap(int axis, bool enable, double offset, double bbox_min);
@@ -52,7 +50,6 @@ protected:
     std::string _travel_to_z(double z, const std::string &comment) override;
 
 private:
-    double          m_belt_angle_rad = 0.;
     BeltBackTransform     m_belt_back_transform;
     MachineFrameTransform m_machine_frame_transform;
     bool            m_origin_snap[3]     = {false, false, false};

src/libslic3r/BeltSliceStrategy.cpp

@@ -17,10 +17,7 @@ std::unique_ptr<BeltSliceStrategy> BeltSliceStrategy::create(const PrintConfig &
 
 BeltSliceStrategy::BeltSliceStrategy(const PrintConfig &config)
 {
-    m_shear    = BeltTransformPipeline::build_shear_matrix(config, &m_has_shear);
-    m_scale    = BeltTransformPipeline::build_scale_matrix(config, &m_has_scale);
     m_rotation = BeltTransformPipeline::build_rotation_matrix(config, &m_has_rotation);
-    m_order    = config.belt_mesh_transform_order.value;
 }
 
 void BeltSliceStrategy::apply_to_trafo(Transform3d &trafo,
@@ -28,15 +25,10 @@ void BeltSliceStrategy::apply_to_trafo(Transform3d &trafo,
                                         bool has_remap,
                                         double *out_belt_min_z) const
 {
-    // ScaleThenShear: applied to a point, scale runs first then shear (m_shear * m_scale).
+    // Rotation is the only mesh-side belt transform (matching build_forward_transform).
-    // ShearThenScale: applied to a point, shear runs first then scale (m_scale * m_shear).
+    if (m_has_rotation) {
-    // Rotation (if active) is applied AFTER shear/scale, matching build_forward_transform.
-    if (m_has_shear || m_has_scale || m_has_rotation) {
-        Matrix3d shear_scale = (m_order == BeltTransformOrder::ScaleThenShear)
-            ? Matrix3d(m_shear * m_scale)
-            : Matrix3d(m_scale * m_shear);
         Transform3d belt_xform = Transform3d::Identity();
-        belt_xform.linear() = Matrix3d(m_rotation * shear_scale);
+        belt_xform.linear() = m_rotation;
         trafo = belt_xform * trafo;
     }
 
@@ -47,7 +39,7 @@ void BeltSliceStrategy::apply_to_trafo(Transform3d &trafo,
     // within the object) causes min_z to be computed against mesh-local vertex
     // coordinates rather than object-space coordinates, so volumes translated
     // along the slicer's Z axis are silently excluded from the bound check.
-    if (has_remap || m_has_shear || m_has_scale || m_has_rotation) {
+    if (has_remap || m_has_rotation) {
         // [BELT-DEBUG] Capture the incoming trafo for diagnostic logging.
         // This is the slicer-frame transform AFTER belt_xform but BEFORE z_shift.
         const Transform3d trafo_pre_shift = trafo;
@@ -65,9 +57,7 @@ void BeltSliceStrategy::apply_to_trafo(Transform3d &trafo,
             ss << "(" << v.x() << "," << v.y() << "," << v.z() << ")";
             return ss.str();
         };
-        BOOST_LOG_TRIVIAL(warning) << "[BELT-DEBUG] apply_to_trafo enter"
+        BOOST_LOG_TRIVIAL(trace) << "[BELT-DEBUG] apply_to_trafo enter"
-            << " has_shear=" << m_has_shear
-            << " has_scale=" << m_has_scale
             << " has_rotation=" << m_has_rotation
             << " has_remap=" << has_remap
             << " trafo.linear=" << log_mat(trafo_pre_shift.linear())
@@ -96,7 +86,7 @@ void BeltSliceStrategy::apply_to_trafo(Transform3d &trafo,
                 vol_min_z = std::min(vol_min_z, pt.z());
                 min_z = std::min(min_z, pt.z());
             }
-            BOOST_LOG_TRIVIAL(warning) << "[BELT-DEBUG]   vol[" << vol_idx
+            BOOST_LOG_TRIVIAL(trace) << "[BELT-DEBUG]   vol[" << vol_idx
                 << "] id=" << mv->id().id << " name='" << mv->name << "'"
                 << " mesh_bbox_min=" << log_vec3(mesh_min) << " mesh_bbox_max=" << log_vec3(mesh_max)
                 << " get_matrix.translation=" << log_vec3(mv->get_matrix().translation())
@@ -105,7 +95,7 @@ void BeltSliceStrategy::apply_to_trafo(Transform3d &trafo,
             ++vol_idx;
         }
         double belt_z_shift_val = (min_z < 0. && min_z != std::numeric_limits<double>::max()) ? -min_z : 0.;
-        BOOST_LOG_TRIVIAL(warning) << "[BELT-DEBUG] combined min_z=" << min_z
+        BOOST_LOG_TRIVIAL(trace) << "[BELT-DEBUG] combined min_z=" << min_z
             << " z_shift_val=" << belt_z_shift_val;
         if (belt_z_shift_val > 0.) {
             Transform3d z_shift = Transform3d::Identity();
@@ -114,11 +104,11 @@ void BeltSliceStrategy::apply_to_trafo(Transform3d &trafo,
         }
         if (out_belt_min_z) {
             double new_val = (min_z != std::numeric_limits<double>::max()) ? min_z : 0.;
-            BOOST_LOG_TRIVIAL(warning) << "[BELT-DEBUG] write m_belt_min_z tid=" << std::this_thread::get_id()
+            BOOST_LOG_TRIVIAL(trace) << "[BELT-DEBUG] write m_belt_min_z tid=" << std::this_thread::get_id()
                 << " target=" << out_belt_min_z << " old=" << *out_belt_min_z << " new=" << new_val;
             *out_belt_min_z = new_val;
         }
-        BOOST_LOG_TRIVIAL(warning) << "[BELT-DEBUG] apply_to_trafo exit"
+        BOOST_LOG_TRIVIAL(trace) << "[BELT-DEBUG] apply_to_trafo exit"
             << " final_trafo.linear=" << log_mat(trafo.linear())
             << " final_trafo.translation=" << log_vec3(trafo.translation());
     }

src/libslic3r/BeltSliceStrategy.hpp

@@ -13,17 +13,17 @@ namespace Slic3r {
 
 // Belt printer pre-slice transform strategy.
 //
-// Encapsulates the pre-remap, shear, scale, and Z-shift transforms
+// Encapsulates the pre-remap, rotation, and Z-shift transforms that are
-// that are applied to model geometry before slicing on belt printers.
+// applied to model geometry before slicing on belt printers.  (Shear & scale
-// Used by PrintObjectSlice.cpp to isolate belt-specific logic from
+// are applied to the g-code, not the mesh.)  Used by PrintObjectSlice.cpp to
-// the slicing pipeline.
+// isolate belt-specific logic from the slicing pipeline.
 class BeltSliceStrategy
 {
 public:
     // Create a strategy if belt_printer is enabled; returns nullptr otherwise.
     static std::unique_ptr<BeltSliceStrategy> create(const PrintConfig &config);
 
-    // Apply belt-specific transforms (shear + scale + z-shift) to the slicing trafo.
+    // Apply belt-specific transforms (rotation + z-shift) to the slicing trafo.
     // Pre-slice remap is handled separately (standalone feature).
     // has_remap: whether pre-slice remap was already applied (affects z-shift detection).
     void apply_to_trafo(Transform3d &trafo,
@@ -34,13 +34,8 @@ public:
 private:
     explicit BeltSliceStrategy(const PrintConfig &config);
 
-    bool               m_has_shear    = false;
+    bool     m_has_rotation = false;
-    bool               m_has_scale    = false;
+    Matrix3d m_rotation     = Matrix3d::Identity();
-    bool               m_has_rotation = false;
-    Matrix3d           m_shear        = Matrix3d::Identity();
-    Matrix3d           m_scale        = Matrix3d::Identity();
-    Matrix3d           m_rotation     = Matrix3d::Identity();
-    BeltTransformOrder m_order        = BeltTransformOrder::ScaleThenShear;
 };
 
 } // namespace Slic3r

src/libslic3r/BeltTransform.cpp

@@ -51,50 +51,6 @@ Transform3d BeltTransformPipeline::build_preslice_remap(const PrintConfig &confi
     return pre_remap;
 }
 
-Matrix3d BeltTransformPipeline::build_shear_matrix(const PrintConfig &config, bool *has_shear_out)
-{
-    struct AxisShear { BeltShearMode mode; double angle; int from; };
-    AxisShear axes[3] = {
-        { config.belt_shear_x.value, config.belt_shear_x_angle.value, int(config.belt_shear_x_from.value) },
-        { config.belt_shear_y.value, config.belt_shear_y_angle.value, int(config.belt_shear_y_from.value) },
-        { config.belt_shear_z.value, config.belt_shear_z_angle.value, int(config.belt_shear_z_from.value) },
-    };
-
-    Matrix3d shear = Matrix3d::Identity();
-    bool active = false;
-    for (int row = 0; row < 3; ++row) {
-        if (axes[row].mode != BeltShearMode::None) {
-            double factor = compute_shear_factor(axes[row].mode, axes[row].angle);
-            if (std::abs(factor) > EPSILON) {
-                shear(row, axes[row].from) += factor;
-                active = true;
-            }
-        }
-    }
-    if (has_shear_out) *has_shear_out = active;
-    return shear;
-}
-
-Matrix3d BeltTransformPipeline::build_scale_matrix(const PrintConfig &config, bool *has_scale_out)
-{
-    double sx = compute_scale_factor(config.belt_scale_x.value, config.belt_scale_x_angle.value);
-    double sy = compute_scale_factor(config.belt_scale_y.value, config.belt_scale_y_angle.value);
-    double sz = compute_scale_factor(config.belt_scale_z.value, config.belt_scale_z_angle.value);
-
-    bool active = (std::abs(sx - 1.) > EPSILON ||
-                   std::abs(sy - 1.) > EPSILON ||
-                   std::abs(sz - 1.) > EPSILON);
-
-    Matrix3d scale = Matrix3d::Identity();
-    if (active) {
-        scale(0, 0) = sx;
-        scale(1, 1) = sy;
-        scale(2, 2) = sz;
-    }
-    if (has_scale_out) *has_scale_out = active;
-    return scale;
-}
-
 Matrix3d BeltTransformPipeline::build_rotation_matrix(const PrintConfig &config, bool *has_rot_out)
 {
     BeltRotationAxis axis = config.belt_slice_rotation.value;
@@ -116,26 +72,13 @@ Matrix3d BeltTransformPipeline::build_rotation_matrix(const PrintConfig &config,
 
 Transform3d BeltTransformPipeline::build_forward_transform(const PrintConfig &config)
 {
-    Transform3d pre_remap    = build_preslice_remap(config);
+    // Mesh-side belt transform: rotation applied after the pre-slice axis remap.
-    bool        shear_active = false;
+    // (Shear & scale are a g-code-side stage, not part of the mesh transform.)
-    Matrix3d    shear        = build_shear_matrix(config, &shear_active);
+    Transform3d pre_remap = build_preslice_remap(config);
-    bool        scale_active = false;
+    Matrix3d    rot       = build_rotation_matrix(config);
-    Matrix3d    scale        = build_scale_matrix(config, &scale_active);
-    bool        rot_active   = false;
-    Matrix3d    rot          = build_rotation_matrix(config, &rot_active);
-
-    // Match the mesh-side ordering selected by belt_mesh_transform_order so
-    // BeltBackTransform inverts the same composition that BeltSliceStrategy
-    // applied to the mesh.
-    //   ScaleThenShear: applied to p, scale runs first then shear (shear * scale).
-    //   ShearThenScale: applied to p, shear runs first then scale (scale * shear).
-    // Rotation is applied AFTER shear/scale: rot * shear_scale * pre_remap.
-    Matrix3d shear_scale = (config.belt_mesh_transform_order.value == BeltTransformOrder::ScaleThenShear)
-        ? Matrix3d(shear * scale)
-        : Matrix3d(scale * shear);
 
     Transform3d combined = Transform3d::Identity();
-    combined.linear() = Matrix3d(rot * shear_scale);
+    combined.linear() = rot;
     combined = combined * pre_remap;
     return combined;
 }
@@ -190,166 +133,75 @@ BeltTransformPipeline::BeltHeightResult compute_belt_height_and_floor_impl(
     BeltTransformPipeline::BeltHeightResult result;
     result.object_height = original_height;
 
-    // Extract Z-axis shear/scale + per-axis scale + transform order + rotation from config.
+    // Extract the mesh rotation from config (the sole mesh-side belt transform).
-    BeltShearMode z_shear_mode;
+    BeltRotationAxis rot_axis;
-    double        z_shear_angle;
+    double           rot_angle;
-    BeltScaleMode z_scale_mode;
-    double        z_scale_angle;
-    int           z_shear_from;
-    BeltScaleMode from_scale_mode;   // scale on the shear's source axis
-    double        from_scale_angle;
-    BeltTransformOrder order;
-    BeltRotationAxis   rot_axis;
-    double             rot_angle;
 
     if constexpr (std::is_same_v<Config, PrintConfig>) {
-        z_shear_mode      = config.belt_shear_z.value;
+        rot_axis  = config.belt_slice_rotation.value;
-        z_shear_angle     = config.belt_shear_z_angle.value;
+        rot_angle = config.belt_slice_rotation_angle.value;
-        z_scale_mode      = config.belt_scale_z.value;
-        z_scale_angle     = config.belt_scale_z_angle.value;
-        z_shear_from      = int(config.belt_shear_z_from.value);
-        order             = config.belt_mesh_transform_order.value;
-        rot_axis          = config.belt_slice_rotation.value;
-        rot_angle         = config.belt_slice_rotation_angle.value;
-        if (z_shear_from == 0) {
-            from_scale_mode  = config.belt_scale_x.value;
-            from_scale_angle = config.belt_scale_x_angle.value;
-        } else {
-            from_scale_mode  = config.belt_scale_y.value;
-            from_scale_angle = config.belt_scale_y_angle.value;
-        }
     } else {
         // DynamicPrintConfig path
-        auto get_shear = [&](const char *key) {
-            auto *opt = config.template option<ConfigOptionEnum<BeltShearMode>>(key);
-            return opt ? opt->value : BeltShearMode::None;
-        };
-        auto get_scale = [&](const char *key) {
-            auto *opt = config.template option<ConfigOptionEnum<BeltScaleMode>>(key);
-            return opt ? opt->value : BeltScaleMode::None;
-        };
         auto get_float = [&](const char *key) {
             auto *opt = config.template option<ConfigOptionFloat>(key);
-            return opt ? opt->value : 45.0;
+            return opt ? opt->value : 0.0;
-        };
-        auto get_axis = [&](const char *key) {
-            auto *opt = config.template option<ConfigOptionEnum<BeltAxis>>(key);
-            return opt ? int(opt->value) : 1;
-        };
-        auto get_order = [&](const char *key) {
-            auto *opt = config.template option<ConfigOptionEnum<BeltTransformOrder>>(key);
-            return opt ? opt->value : BeltTransformOrder::ScaleThenShear;
         };
         auto get_rot_axis = [&](const char *key) {
             auto *opt = config.template option<ConfigOptionEnum<BeltRotationAxis>>(key);
             return opt ? opt->value : BeltRotationAxis::None;
         };
-        z_shear_mode  = get_shear("belt_shear_z");
+        rot_axis  = get_rot_axis("belt_slice_rotation");
-        z_shear_angle = get_float("belt_shear_z_angle");
+        rot_angle = get_float("belt_slice_rotation_angle");
-        z_scale_mode  = get_scale("belt_scale_z");
-        z_scale_angle = get_float("belt_scale_z_angle");
-        z_shear_from  = get_axis("belt_shear_z_from");
-        order         = get_order("belt_mesh_transform_order");
-        rot_axis      = get_rot_axis("belt_slice_rotation");
-        rot_angle     = get_float("belt_slice_rotation_angle");
-        if (z_shear_from == 0) {
-            from_scale_mode  = get_scale("belt_scale_x");
-            from_scale_angle = get_float("belt_scale_x_angle");
-        } else {
-            from_scale_mode  = get_scale("belt_scale_y");
-            from_scale_angle = get_float("belt_scale_y_angle");
-        }
     }
 
-    bool has_z_shear  = z_shear_mode != BeltShearMode::None;
-    bool has_z_scale  = z_scale_mode != BeltScaleMode::None;
     bool has_rotation = rot_axis != BeltRotationAxis::None && std::abs(rot_angle) > EPSILON;
-
+    if (!has_rotation)
-    if (!has_z_shear && !has_z_scale && !has_rotation)
         return result;
 
-    double shear_factor = has_z_shear
+    // Rotation path: sweep the 8 bbox corners through R to get the rotated height,
-        ? BeltTransformPipeline::compute_shear_factor(z_shear_mode, z_shear_angle) : 0.;
+    // then derive the belt floor (the image of machine-Z = 0 under R).
-    double scale_z    = BeltTransformPipeline::compute_scale_factor(z_scale_mode, z_scale_angle);
+    double angle_rad = Geometry::deg2rad(rot_angle);
-    double scale_from = BeltTransformPipeline::compute_scale_factor(from_scale_mode, from_scale_angle);
+    Vec3d unit_axis;
-
+    switch (rot_axis) {
-    if (has_z_shear && std::abs(shear_factor) > EPSILON) {
+    case BeltRotationAxis::X: unit_axis = Vec3d::UnitX(); break;
-        int from = z_shear_from;
+    case BeltRotationAxis::Y: unit_axis = Vec3d::UnitY(); break;
-        double min_rz = std::numeric_limits<double>::max();
+    case BeltRotationAxis::Z: unit_axis = Vec3d::UnitZ(); break;
-        double max_rz = std::numeric_limits<double>::lowest();
+    default:                  unit_axis = Vec3d::UnitX(); break;
-        for (double vz : {bb.min.z(), bb.max.z()})
-            for (double vs : {bb.min(from), bb.max(from)}) {
-                // Mesh-frame new_z computed per ordering.
-                //   scale-then-shear: Z_s = sz*Z_m + s_from*tan(α)*from_m
-                //   shear-then-scale: Z_s = sz*(Z_m + tan(α)*from_m)
-                double new_z = (order == BeltTransformOrder::ScaleThenShear)
-                    ? scale_z * vz + scale_from * shear_factor * vs
-                    : scale_z * (vz + shear_factor * vs);
-                min_rz = std::min(min_rz, new_z);
-                max_rz = std::max(max_rz, new_z);
-            }
-        result.object_height          = max_rz - min_rz;
-        // Effective slicer-frame slope of the belt surface (Z_m=0 line):
-        //   scale-then-shear: Z_s = tan(α) * Y_s          → slope = tan(α)
-        //   shear-then-scale: Z_s = sz/s_from * tan(α) * Y_s → slope = sz*tan(α)/s_from
-        // The downstream cutoff formula `Y_s = (print_z - z_shift) / slope`
-        // and floor_print_z(Y_s) = slope * Y_s + z_shift use this slope.
-        double effective_shear = (order == BeltTransformOrder::ScaleThenShear)
-            ? shear_factor
-            : (std::abs(scale_from) > EPSILON
-                ? scale_z * shear_factor / scale_from
-                : shear_factor);
-        result.floor_params.shear_factor = effective_shear;
-        result.floor_params.from_axis    = from;
-        result.floor_params.z_shift      = bb.min.z() + ((min_rz < 0.) ? -min_rz : 0.);
-    } else if (has_rotation) {
-        // Rotation-only path (no Z-shear): sweep 8 bbox corners through 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);
-        }
-        // Optional Z-scale still applies multiplicatively if both are set.
-        result.object_height = (max_rz - min_rz) * (has_z_scale ? scale_z : 1.0);
-
-        // 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.);
-    } else {
-        result.object_height = original_height * scale_z;
     }
+    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;
 }

src/libslic3r/BeltTransform.hpp

@@ -15,11 +15,16 @@ class ModelObject;
 // Shared belt-printer transform math.
 //
 // The pre-slice pipeline applied in PrintObjectSlice.cpp is:
-//     trafo_out = z_shift * scale * shear * pre_remap * trafo_in
+//     trafo_out = z_shift * rotation * pre_remap * trafo_in
 //
-// This class provides the building blocks so every call site uses the
+// Rotation is the sole mesh-side belt transform; shear & scale are applied
-// same implementation.  z_shift is object-dependent (computed from mesh
+// to the g-code instead (see MachineFrameTransform).  This class provides the
-// vertex bounds) and is NOT included in build_forward_transform().
+// 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 compute_shear_factor / compute_scale_factor math helpers below are still
+// used by the g-code-side machine-frame shear/scale.
 class BeltTransformPipeline
 {
 public:
@@ -75,50 +80,53 @@ public:
                get_int("preslice_remap_z") != int(RemapAxis::PosZ);
     }
 
-    static bool has_shear(const PrintConfig &config)
-    {
-        return config.belt_shear_x.value != BeltShearMode::None ||
-               config.belt_shear_y.value != BeltShearMode::None ||
-               config.belt_shear_z.value != BeltShearMode::None;
-    }
-
-    static bool has_scale(const PrintConfig &config)
-    {
-        double sx = compute_scale_factor(config.belt_scale_x.value, config.belt_scale_x_angle.value);
-        double sy = compute_scale_factor(config.belt_scale_y.value, config.belt_scale_y_angle.value);
-        double sz = compute_scale_factor(config.belt_scale_z.value, config.belt_scale_z_angle.value);
-        return std::abs(sx - 1.) > EPSILON ||
-               std::abs(sy - 1.) > EPSILON ||
-               std::abs(sz - 1.) > EPSILON;
-    }
-
     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 shear matrix.  Returns Identity if no shear is active.
-    // Also sets has_shear_out if non-null.
-    static Matrix3d build_shear_matrix(const PrintConfig &config, bool *has_shear_out = nullptr);
-
-    // Build the 3x3 diagonal scale matrix.  Returns Identity if no scale.
-    // Also sets has_scale_out if non-null.
-    static Matrix3d build_scale_matrix(const PrintConfig &config, bool *has_scale_out = nullptr);
-
     // 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.  Shear/scale order is selected by
+    // Combined forward transform (rotation * pre_remap) — the mesh-side belt
-    // belt_mesh_transform_order so the result matches what BeltSliceStrategy
+    // transform that BeltSliceStrategy applies and BeltBackTransform inverts.
-    // applied to the mesh (BeltBackTransform inverts this).
     // Does NOT include the per-object Z-shift.
     static Transform3d build_forward_transform(const PrintConfig &config);
 

src/libslic3r/FirstLayerPlane.cpp

@@ -85,9 +85,8 @@ FirstLayerPlane::FirstLayerPlane(const PrintConfig &config)
     FirstLayerPlaneMode mode = config.first_layer_plane.value;
     if (mode == FirstLayerPlaneMode::Auto) {
         bool belt_affine_active = config.belt_printer.value &&
-            (config.belt_shear_z.value != BeltShearMode::None ||
+            config.belt_slice_rotation.value != BeltRotationAxis::None &&
-             (config.belt_slice_rotation.value != BeltRotationAxis::None &&
+            std::abs(config.belt_slice_rotation_angle.value) > EPSILON;
-              std::abs(config.belt_slice_rotation_angle.value) > EPSILON));
         mode = belt_affine_active ? FirstLayerPlaneMode::BeltAffine
                                   : FirstLayerPlaneMode::XY;
     }

src/libslic3r/GCode.cpp

@@ -6520,14 +6520,14 @@ std::string GCode::_extrude(const ExtrusionPath &path, std::string description,
     auto _mm3_per_mm = path.mm3_per_mm * this->config().print_flow_ratio;
     _mm3_per_mm *= filament_flow_ratio;
 
-    // Belt printer: compensate for the volume change introduced by the mesh
+    // Belt printer: compensate for any volume change introduced by the mesh
     // forward transform.  path.mm3_per_mm is derived from slicer-frame layer
     // height × line width, but a slicer-frame slab of volume V maps under the
-    // back-transform to a machine-frame region of volume V / |det(T)|.  When
+    // back-transform to a machine-frame region of volume V / |det(T)|.  The
-    // det(T) > 1 — e.g. belt_scale_y = 1/cos(α) ≈ 1.155 at α = 30° — the
+    // mesh transform is now rotation ∘ pre-remap, both orthogonal, so |det(T)|
-    // machine slab holds less plastic than the slicer thinks it is filling
+    // is always 1 and this is currently a no-op; it is retained as a guard in
-    // and we over-extrude by det(T).  Pure shear has det 1, so this is a
+    // case a non-orthogonal mesh transform is ever reintroduced.  (Machine-frame
-    // no-op until scale factors deviate from 1.
+    // shear/scale acts on the g-code in BeltGCodeWriter, not here.)
     if (m_config.belt_printer.value) {
         double det = std::abs(BeltTransformPipeline::build_forward_transform(m_config).linear().determinant());
         if (det > EPSILON)

src/libslic3r/GCode/BeltBackTransform.cpp

@@ -12,18 +12,15 @@ bool BeltBackTransform::init_from_config(const PrintConfig &config)
         return false;
 
     // Require at least one active transform to proceed.
-    bool has_global_shear = config.belt_shear_x_global.value ||
-                            config.belt_shear_y_global.value ||
-                            config.belt_shear_z_global.value;
     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_shear && !has_global_rotation && !has_preslice_global
+    if (!has_global_rotation && !has_preslice_global
         && !BeltTransformPipeline::has_preslice_remap(config))
         return false;
 
-    // Build the forward pipeline (scale * shear * pre_remap) and store its inverse.
+    // 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;

src/libslic3r/GCode/GCodeProcessor.cpp

@@ -3072,90 +3072,21 @@ void GCodeProcessor::process_tags(const std::string_view comment, bool producers
         return;
     }
 
-    // Belt printer angle detection from G-code header comment.
+    // Belt printer: derive the physical tilt magnitude from the slicing-rotation
-    if (boost::starts_with(comment, " belt_printer_angle = ")) {
+    // angle header comment (used to enable the preview's belt view).
+    if (boost::starts_with(comment, " belt_slice_rotation_angle = ")) {
         try {
-            m_result.belt_printer_angle = std::stof(std::string(comment.substr(22)));
+            m_result.belt_tilt_angle = std::abs(std::stof(std::string(comment.substr(29))));
         } catch (...) {}
         return;
     }
-    // Belt printer: parse shear configs from header comments.
+    // Belt printer: parse pre-slice axis remap from header comments.
     {
-        auto parse_shear_mode = [](const std::string &s) -> BeltShearMode {
-            if (s == "pos_cot") return BeltShearMode::PosCot;
-            if (s == "neg_cot") return BeltShearMode::NegCot;
-            if (s == "pos_tan") return BeltShearMode::PosTan;
-            if (s == "neg_tan") return BeltShearMode::NegTan;
-            return BeltShearMode::None;
-        };
-        auto parse_axis = [](const std::string &s) -> BeltAxis {
-            if (s == "y") return BeltAxis::Y;
-            if (s == "z") return BeltAxis::Z;
-            return BeltAxis::X;
-        };
-        auto parse_scale_mode = [](const std::string &s) -> BeltScaleMode {
-            if (s == "inv_sin") return BeltScaleMode::InvSin;
-            if (s == "inv_cos") return BeltScaleMode::InvCos;
-            if (s == "sin")     return BeltScaleMode::Sin;
-            if (s == "cos")     return BeltScaleMode::Cos;
-            return BeltScaleMode::None;
-        };
         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);
         };
-        // Shear X
-        if (boost::starts_with(comment, " belt_shear_x = ")) {
-            m_result.belt_shear_x = parse_shear_mode(trim(std::string(comment.substr(16)))); return;
-        }
-        if (boost::starts_with(comment, " belt_shear_x_angle = ")) {
-            try { m_result.belt_shear_x_angle = std::stof(std::string(comment.substr(22))); } catch (...) {} return;
-        }
-        if (boost::starts_with(comment, " belt_shear_x_from = ")) {
-            m_result.belt_shear_x_from = parse_axis(trim(std::string(comment.substr(21)))); return;
-        }
-        // Shear Y
-        if (boost::starts_with(comment, " belt_shear_y = ")) {
-            m_result.belt_shear_y = parse_shear_mode(trim(std::string(comment.substr(16)))); return;
-        }
-        if (boost::starts_with(comment, " belt_shear_y_angle = ")) {
-            try { m_result.belt_shear_y_angle = std::stof(std::string(comment.substr(22))); } catch (...) {} return;
-        }
-        if (boost::starts_with(comment, " belt_shear_y_from = ")) {
-            m_result.belt_shear_y_from = parse_axis(trim(std::string(comment.substr(21)))); return;
-        }
-        // Shear Z
-        if (boost::starts_with(comment, " belt_shear_z = ")) {
-            m_result.belt_shear_z = parse_shear_mode(trim(std::string(comment.substr(16)))); return;
-        }
-        if (boost::starts_with(comment, " belt_shear_z_angle = ")) {
-            try { m_result.belt_shear_z_angle = std::stof(std::string(comment.substr(22))); } catch (...) {} return;
-        }
-        if (boost::starts_with(comment, " belt_shear_z_from = ")) {
-            m_result.belt_shear_z_from = parse_axis(trim(std::string(comment.substr(21)))); return;
-        }
-        // Scale X
-        if (boost::starts_with(comment, " belt_scale_x = ")) {
-            m_result.belt_scale_x = parse_scale_mode(trim(std::string(comment.substr(16)))); return;
-        }
-        if (boost::starts_with(comment, " belt_scale_x_angle = ")) {
-            try { m_result.belt_scale_x_angle = std::stof(std::string(comment.substr(22))); } catch (...) {} return;
-        }
-        // Scale Y
-        if (boost::starts_with(comment, " belt_scale_y = ")) {
-            m_result.belt_scale_y = parse_scale_mode(trim(std::string(comment.substr(16)))); return;
-        }
-        if (boost::starts_with(comment, " belt_scale_y_angle = ")) {
-            try { m_result.belt_scale_y_angle = std::stof(std::string(comment.substr(22))); } catch (...) {} return;
-        }
-        // Scale Z
-        if (boost::starts_with(comment, " belt_scale_z = ")) {
-            m_result.belt_scale_z = parse_scale_mode(trim(std::string(comment.substr(16)))); return;
-        }
-        if (boost::starts_with(comment, " belt_scale_z_angle = ")) {
-            try { m_result.belt_scale_z_angle = std::stof(std::string(comment.substr(22))); } catch (...) {} return;
-        }
         // Pre-slice axis remap
         auto parse_remap_axis = [](const std::string &s) -> RemapAxis {
             if (s == "pos_x") return RemapAxis::PosX;

src/libslic3r/GCode/GCodeProcessor.hpp

@@ -245,25 +245,9 @@ class Print;
         bool support_traditional_timelapse{true};
         float printable_height;
         float z_offset;
-        // Belt printer: angle for coordinate transformation in preview.
+        // Belt printer: physical tilt magnitude (deg) parsed from the slicing-rotation
-        float belt_printer_angle{ 0.f };
+        // header comment; used to enable the preview's belt view.
-        // Belt printer: per-axis shear config.
+        float belt_tilt_angle{ 0.f };
-        BeltShearMode belt_shear_x{ BeltShearMode::None };
-        float         belt_shear_x_angle{ 45.f };
-        BeltAxis      belt_shear_x_from{ BeltAxis::Y };
-        BeltShearMode belt_shear_y{ BeltShearMode::None };
-        float         belt_shear_y_angle{ 45.f };
-        BeltAxis      belt_shear_y_from{ BeltAxis::Y };
-        BeltShearMode belt_shear_z{ BeltShearMode::None };
-        float         belt_shear_z_angle{ 45.f };
-        BeltAxis      belt_shear_z_from{ BeltAxis::Y };
-        // Belt printer: per-axis scale config.
-        BeltScaleMode belt_scale_x{ BeltScaleMode::None };
-        float         belt_scale_x_angle{ 45.f };
-        BeltScaleMode belt_scale_y{ BeltScaleMode::None };
-        float         belt_scale_y_angle{ 45.f };
-        BeltScaleMode belt_scale_z{ BeltScaleMode::None };
-        float         belt_scale_z_angle{ 45.f };
         RemapAxis preslice_remap_x{ RemapAxis::PosX };
         RemapAxis preslice_remap_y{ RemapAxis::PosY };
         RemapAxis preslice_remap_z{ RemapAxis::PosZ };
@@ -332,22 +316,7 @@ class Print;
             optimal_assignment = other.optimal_assignment;
             filament_change_count_map = other.filament_change_count_map;
             initial_layer_time = other.initial_layer_time;
-            belt_printer_angle = other.belt_printer_angle;
+            belt_tilt_angle = other.belt_tilt_angle;
-            belt_shear_x = other.belt_shear_x;
-            belt_shear_x_angle = other.belt_shear_x_angle;
-            belt_shear_x_from = other.belt_shear_x_from;
-            belt_shear_y = other.belt_shear_y;
-            belt_shear_y_angle = other.belt_shear_y_angle;
-            belt_shear_y_from = other.belt_shear_y_from;
-            belt_shear_z = other.belt_shear_z;
-            belt_shear_z_angle = other.belt_shear_z_angle;
-            belt_shear_z_from = other.belt_shear_z_from;
-            belt_scale_x = other.belt_scale_x;
-            belt_scale_x_angle = other.belt_scale_x_angle;
-            belt_scale_y = other.belt_scale_y;
-            belt_scale_y_angle = other.belt_scale_y_angle;
-            belt_scale_z = other.belt_scale_z;
-            belt_scale_z_angle = other.belt_scale_z_angle;
             preslice_remap_x = other.preslice_remap_x;
             preslice_remap_y = other.preslice_remap_y;
             preslice_remap_z = other.preslice_remap_z;

src/libslic3r/GCode/MachineFrameTransform.cpp

@@ -6,50 +6,6 @@ namespace Slic3r {
 
 namespace {
 
-// Build the post-gcode axis-remap transform (mirrors BeltTransformPipeline::build_preslice_remap
-// but reads post_gcode_remap_* keys).  Includes Rev-mode translation derived from build volume.
-Transform3d build_post_gcode_remap(const PrintConfig &config)
-{
-    Transform3d remap = Transform3d::Identity();
-
-    int rx = int(config.post_gcode_remap_x.value);
-    int ry = int(config.post_gcode_remap_y.value);
-    int rz = int(config.post_gcode_remap_z.value);
-
-    if (rx == int(RemapAxis::PosX) && ry == int(RemapAxis::PosY) && rz == int(RemapAxis::PosZ))
-        return remap;
-
-    auto remap_column = [](int r) -> Vec3d {
-        int axis = r % 3;
-        Vec3d col = Vec3d::Zero();
-        if (r < 3)      col[axis] =  1.0;
-        else if (r < 6) col[axis] = -1.0;
-        else            col[axis] = -1.0;  // Rev: max - pos
-        return col;
-    };
-
-    Matrix3d lin;
-    lin.col(0) = remap_column(rx);
-    lin.col(1) = remap_column(ry);
-    lin.col(2) = remap_column(rz);
-    remap.linear() = lin;
-
-    if (rx >= 6 || ry >= 6 || 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 trans = Vec3d::Zero();
-        auto add_rev = [&](int r, int out) {
-            if (r >= 6) trans[out] = vol_max[r % 3];
-        };
-        add_rev(rx, 0);
-        add_rev(ry, 1);
-        add_rev(rz, 2);
-        remap.translation() = trans;
-    }
-
-    return remap;
-}
-
 // Build the 3x3 shear matrix from gcode_shear_* keys.
 Matrix3d build_gcode_shear_matrix(const PrintConfig &config, bool &active)
 {
@@ -94,13 +50,6 @@ Matrix3d build_gcode_scale_matrix(const PrintConfig &config, bool &active)
     return scale;
 }
 
-bool has_post_gcode_remap(const PrintConfig &config)
-{
-    return int(config.post_gcode_remap_x.value) != int(RemapAxis::PosX) ||
-           int(config.post_gcode_remap_y.value) != int(RemapAxis::PosY) ||
-           int(config.post_gcode_remap_z.value) != int(RemapAxis::PosZ);
-}
-
 } // namespace
 
 bool MachineFrameTransform::init_from_config(const PrintConfig &config)
@@ -111,13 +60,12 @@ bool MachineFrameTransform::init_from_config(const PrintConfig &config)
     if (!config.belt_printer.value)
         return false;
 
-    Transform3d post_remap   = build_post_gcode_remap(config);
     bool        shear_active = false;
     Matrix3d    shear        = build_gcode_shear_matrix(config, shear_active);
     bool        scale_active = false;
     Matrix3d    scale        = build_gcode_scale_matrix(config, scale_active);
 
-    if (!shear_active && !scale_active && !has_post_gcode_remap(config))
+    if (!shear_active && !scale_active)
         return false;
 
     // Compose per belt_gcode_transform_order:
@@ -127,7 +75,6 @@ bool MachineFrameTransform::init_from_config(const PrintConfig &config)
     combined.linear() = (config.belt_gcode_transform_order.value == BeltTransformOrder::ScaleThenShear)
         ? Matrix3d(shear * scale)
         : Matrix3d(scale * shear);
-    combined = combined * post_remap;
 
     if (combined.isApprox(Transform3d::Identity()))
         return false;

src/libslic3r/GCode/MachineFrameTransform.hpp

@@ -9,15 +9,14 @@ namespace Slic3r {
 
 // Post-stage machine-frame transform for belt printers.
 //
-// Applied in BeltGCodeWriter::to_machine_coords AFTER the back-transform
+// Applied in BeltGCodeWriter::to_machine_coords AFTER the back-transform,
-// and the existing gcode_remap_* axis remap, and BEFORE per-axis origin snap.
+// the gcode_remap_* axis remap and per-axis origin snap.  Maps Cartesian
-// Maps Cartesian (axis-permuted) G-code coordinates into the printer's
+// (axis-permuted) G-code coordinates into the printer's physical machine
-// physical machine frame using a parallel set of options:
+// frame using:
 //   gcode_shear_x/y/z + _angle + _from
 //   gcode_scale_x/y/z + _angle
-//   post_gcode_remap_x/y/z
 //
-// Composition matches the mesh-side pipeline: shear * scale * post_remap.
+// Composition follows belt_gcode_transform_order (shear * scale or scale * shear).
 class MachineFrameTransform
 {
 public:
@@ -25,7 +24,7 @@ public:
 
     // Initialize from belt printer config.  Returns true if a non-identity
     // transform was computed.  Inactive when belt_printer is disabled or
-    // all three sub-stages are identity.
+    // 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.

src/libslic3r/Preset.cpp

@@ -1318,12 +1318,8 @@ static std::vector<std::string> s_Preset_machine_limits_options {
 
 static std::vector<std::string> s_Preset_printer_options {
     "printer_technology",
-    "printable_area", "extruder_printable_area", "bed_exclude_area","bed_custom_texture", "bed_custom_model", "build_plate_tilt_x", "build_plate_tilt_y", "belt_printer", "belt_printer_angle", "belt_printer_infinite_y", "belt_shear_x", "belt_shear_x_angle", "belt_shear_x_from", "belt_shear_x_global",
+    "printable_area", "extruder_printable_area", "bed_exclude_area","bed_custom_texture", "bed_custom_model", "build_plate_tilt_x", "build_plate_tilt_y", "belt_printer", "belt_printer_infinite_y",
-    "belt_shear_y", "belt_shear_y_angle", "belt_shear_y_from", "belt_shear_y_global",
-    "belt_shear_z", "belt_shear_z_angle", "belt_shear_z_from", "belt_shear_z_global",
-    "belt_scale_x", "belt_scale_x_angle", "belt_scale_y", "belt_scale_y_angle", "belt_scale_z", "belt_scale_z_angle",
     "belt_slice_rotation", "belt_slice_rotation_angle", "belt_slice_rotation_global",
-    "belt_mesh_transform_order",
     "preslice_remap_x", "preslice_remap_y", "preslice_remap_z", "preslice_remap_global",
     "gcode_remap_x", "gcode_remap_y", "gcode_remap_z", "gcode_back_transform",
     "gcode_shear_x", "gcode_shear_x_angle", "gcode_shear_x_from",
@@ -1333,7 +1329,6 @@ static std::vector<std::string> s_Preset_printer_options {
     "gcode_scale_y", "gcode_scale_y_angle",
     "gcode_scale_z", "gcode_scale_z_angle",
     "belt_gcode_transform_order",
-    "post_gcode_remap_x", "post_gcode_remap_y", "post_gcode_remap_z",
     "belt_preslice_global",
     "first_layer_plane", "first_layer_plane_offset", "first_layer_plane_thickness",
     "belt_origin_snap_x", "belt_origin_offset_x",

src/libslic3r/Print.cpp

@@ -112,7 +112,6 @@ bool Print::invalidate_state_by_config_options(const ConfigOptionResolver & /* n
         "gcode_scale_y", "gcode_scale_y_angle",
         "gcode_scale_z", "gcode_scale_z_angle",
         "belt_gcode_transform_order",
-        "post_gcode_remap_x", "post_gcode_remap_y", "post_gcode_remap_z",
         "belt_origin_snap_x", "belt_origin_offset_x",
         "belt_origin_snap_y", "belt_origin_offset_y",
         "belt_origin_snap_z", "belt_origin_offset_z",
@@ -301,26 +300,9 @@ bool Print::invalidate_state_by_config_options(const ConfigOptionResolver & /* n
             || opt_key == "build_plate_tilt_y"
             // Belt printer transform options change the mesh geometry before slicing.
             || opt_key == "belt_printer"
-            || opt_key == "belt_printer_angle"
+            || opt_key == "belt_slice_rotation"
-            || opt_key == "belt_shear_x"
+            || opt_key == "belt_slice_rotation_angle"
-            || opt_key == "belt_shear_x_angle"
+            || opt_key == "belt_slice_rotation_global"
-            || opt_key == "belt_shear_x_from"
-            || opt_key == "belt_shear_x_global"
-            || opt_key == "belt_shear_y"
-            || opt_key == "belt_shear_y_angle"
-            || opt_key == "belt_shear_y_from"
-            || opt_key == "belt_shear_y_global"
-            || opt_key == "belt_shear_z"
-            || opt_key == "belt_shear_z_angle"
-            || opt_key == "belt_shear_z_from"
-            || opt_key == "belt_shear_z_global"
-            || opt_key == "belt_scale_x"
-            || opt_key == "belt_scale_x_angle"
-            || opt_key == "belt_scale_y"
-            || opt_key == "belt_scale_y_angle"
-            || opt_key == "belt_scale_z"
-            || opt_key == "belt_scale_z_angle"
-            || opt_key == "belt_mesh_transform_order"
             || opt_key == "belt_preslice_global"
             || opt_key == "preslice_remap_global"
             || opt_key == "preslice_remap_x"
@@ -2284,10 +2266,13 @@ void Print::process(long long *time_cost_with_cache, bool use_cache)
     int object_count = m_objects.size();
     std::set<PrintObject*> need_slicing_objects;
     std::set<PrintObject*> re_slicing_objects;
-    // Belt global Z shear: each object needs unique layer Z values based on
+    // Belt global modes couple each object's bed position into its layer Z values,
-    // its bed position, so sharing layers between "identical" objects is wrong.
+    // so sharing layers between "identical" objects is wrong.
-    bool belt_no_share = m_config.belt_printer.value && m_config.belt_shear_z_global.value
+    bool belt_no_share = m_config.belt_printer.value &&
-        && m_config.belt_shear_z.value != BeltShearMode::None;
+        ((m_config.belt_slice_rotation_global.value
+              && m_config.belt_slice_rotation.value != BeltRotationAxis::None)
+         || m_config.preslice_remap_global.value
+         || m_config.belt_preslice_global.value);
     if (!use_cache) {
         for (int index = 0; index < object_count; index++)
         {

src/libslic3r/PrintApply.cpp

@@ -1537,8 +1537,7 @@ Print::ApplyStatus Print::apply(const Model &model, DynamicPrintConfig new_full_
             // Belt global mode: force each instance into its own PrintObject
             // so each gets independent layer Z values.
             bool belt_force_separate = m_config.belt_printer.value && (
-                (m_config.belt_shear_z_global.value && m_config.belt_shear_z.value != BeltShearMode::None)
+                (m_config.belt_slice_rotation_global.value
-                || (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)
                 || m_config.belt_preslice_global.value
@@ -1633,8 +1632,7 @@ Print::ApplyStatus Print::apply(const Model &model, DynamicPrintConfig new_full_
         // min_shift across all objects, so one move affects everyone).
         if (belt_instances_shifted
             && m_config.belt_printer.value
-            && ((m_config.belt_shear_z_global.value && m_config.belt_shear_z.value != BeltShearMode::None)
+            && ((m_config.belt_slice_rotation_global.value
-                || (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)
                 || m_config.belt_preslice_global.value

src/libslic3r/PrintConfig.cpp

@@ -1,5 +1,6 @@
 #include "PrintConfig.hpp"
 #include "PrintConfigConstants.hpp"
+#include "BeltTransform.hpp"
 #include "ClipperUtils.hpp"
 #include "Config.hpp"
 #include "Geometry.hpp"
@@ -6388,18 +6389,6 @@ void PrintConfigDef::init_fff_params()
     def->mode = comAdvanced;
     def->set_default_value(new ConfigOptionBool(false));
 
-    def = this->add("belt_printer_angle", coFloat);
-    def->label = L("Belt angle");
-    def->category = L("Printable space");
-    def->tooltip = L("The tilt angle of the belt surface in degrees. "
-                     "Most belt printers use a 45-degree angle. "
-                     "This controls the rotation applied to the slicing plane and G-code coordinates.");
-    def->sidetext = u8"\u00B0";
-    def->min = 0;
-    def->max = 90;
-    def->mode = comAdvanced;
-    def->set_default_value(new ConfigOptionFloat(45.));
-
     def = this->add("belt_printer_infinite_y", coBool);
     def->label = L("Infinite Y axis");
     def->category = L("Printable space");
@@ -6409,134 +6398,42 @@ void PrintConfigDef::init_fff_params()
     def->mode = comAdvanced;
     def->set_default_value(new ConfigOptionBool(true));
 
-    // Per-axis shear controls for belt printer
+    // Mesh rotation applied before slicing — the sole mesh-side belt transform AND
-    auto add_belt_shear_mode = [this](const char *key, const char *label, BeltShearMode default_mode,
+    // the single source of truth for the physical belt tilt (bed rendering, support
-                                       ConfigOptionMode mode = comAdvanced) {
+    // gravity tilt and bed-exclusion projection all derive their angle from this).
-        auto def = this->add(key, coEnum);
-        def->label = L(label);
-        def->category = L("Printable space");
-        def->tooltip = L("Shear function applied to this axis in belt printer mode.");
-        def->enum_keys_map = &ConfigOptionEnum<BeltShearMode>::get_enum_values();
-        def->enum_values  = {"none", "pos_cot", "neg_cot", "pos_tan", "neg_tan"};
-        def->enum_labels  = {L("None"), L("+cot(α)"), L("-cot(α)"), L("+tan(α)"), L("-tan(α)")};
-        def->mode = mode;
-        def->set_default_value(new ConfigOptionEnum<BeltShearMode>(default_mode));
-    };
-    auto add_belt_shear_angle = [this](const char *key, const char *label,
-                                        ConfigOptionMode mode = comAdvanced) {
-        auto def = this->add(key, coFloat);
-        def->label = L(label);
-        def->category = L("Printable space");
-        def->tooltip = L("Angle (degrees) for the shear function on this axis.");
-        def->sidetext = L("°");
-        def->min = 0.1;
-        def->max = 89.9;
-        def->mode = mode;
-        def->set_default_value(new ConfigOptionFloat(45));
-    };
-    auto add_belt_axis_enum = [this](const char *key, const char *label, const char *tooltip,
-                                      BeltAxis default_axis, ConfigOptionMode mode = comAdvanced) {
-        auto def = this->add(key, coEnum);
-        def->label = L(label);
-        def->category = L("Printable space");
-        def->tooltip = L(tooltip);
-        def->enum_keys_map = &ConfigOptionEnum<BeltAxis>::get_enum_values();
-        def->enum_values  = {"x", "y", "z"};
-        def->enum_labels  = {L("X"), L("Y"), L("Z")};
-        def->mode = mode;
-        def->set_default_value(new ConfigOptionEnum<BeltAxis>(default_axis));
-    };
-
-    auto add_belt_shear_global = [this](const char *key, const char *label, bool default_val = false) {
-        auto def = this->add(key, coBool);
-        def->label = L(label);
-        def->category = L("Printable space");
-        def->tooltip = L("Apply shear in global coordinates (position-aware) rather than object-local coordinates.");
-        def->mode = comExpert;
-        def->set_default_value(new ConfigOptionBool(default_val));
-    };
-
-    add_belt_shear_mode ("belt_shear_x", "Function", BeltShearMode::None, comExpert);
-    add_belt_shear_angle("belt_shear_x_angle", "Angle", comExpert);
-    add_belt_axis_enum  ("belt_shear_x_from", "From", "Source axis for X shear.", BeltAxis::Z, comExpert);
-    add_belt_shear_global("belt_shear_x_global", "Global");
-
-    add_belt_shear_mode ("belt_shear_y", "Function", BeltShearMode::None, comExpert);
-    add_belt_shear_angle("belt_shear_y_angle", "Angle", comExpert);
-    add_belt_axis_enum  ("belt_shear_y_from", "From", "Source axis for Y shear.", BeltAxis::Z, comExpert);
-    add_belt_shear_global("belt_shear_y_global", "Global");
-
-    add_belt_shear_mode ("belt_shear_z", "Function", BeltShearMode::None, comExpert);
-    add_belt_shear_angle("belt_shear_z_angle", "Angle", comExpert);
-    add_belt_axis_enum  ("belt_shear_z_from", "From", "Source axis for Z shear.", BeltAxis::Y, comExpert);
-    add_belt_shear_global("belt_shear_z_global", "Global", true);
-
-    // Per-axis scale controls for belt printer
-    auto add_belt_scale_mode = [this](const char *key, const char *label, BeltScaleMode default_mode,
-                                       ConfigOptionMode mode = comAdvanced) {
-        auto def = this->add(key, coEnum);
-        def->label = L(label);
-        def->category = L("Printable space");
-        def->tooltip = L("Scale factor applied to this axis in belt printer mode.");
-        def->enum_keys_map = &ConfigOptionEnum<BeltScaleMode>::get_enum_values();
-        def->enum_values  = {"none", "inv_sin", "inv_cos", "sin", "cos"};
-        def->enum_labels  = {L("None"), L("1/sin(α)"), L("1/cos(α)"), L("sin(α)"), L("cos(α)")};
-        def->mode = mode;
-        def->set_default_value(new ConfigOptionEnum<BeltScaleMode>(default_mode));
-    };
-    auto add_belt_scale_angle = [this](const char *key, const char *label,
-                                        ConfigOptionMode mode = comAdvanced) {
-        auto def = this->add(key, coFloat);
-        def->label = L(label);
-        def->category = L("Printable space");
-        def->tooltip = L("Angle (degrees) for the scale function on this axis.");
-        def->sidetext = L("°");
-        def->min = 0.1;
-        def->max = 89.9;
-        def->mode = mode;
-        def->set_default_value(new ConfigOptionFloat(45));
-    };
-
-    add_belt_scale_mode ("belt_scale_x", "Function", BeltScaleMode::None, comExpert);
-    add_belt_scale_angle("belt_scale_x_angle", "Angle", comExpert);
-
-    add_belt_scale_mode ("belt_scale_y", "Function", BeltScaleMode::None, comExpert);
-    add_belt_scale_angle("belt_scale_y_angle", "Angle", comExpert);
-
-    add_belt_scale_mode ("belt_scale_z", "Function", BeltScaleMode::None, comExpert);
-    add_belt_scale_angle("belt_scale_z_angle", "Angle", comExpert);
-
-    // Global slicing rotation (alternative to per-axis shear+scale).
     def = this->add("belt_slice_rotation", coEnum);
-    def->label = L("Slicing rotation axis");
+    def->label = L("Belt tilt axis");
     def->category = L("Printable space");
-    def->tooltip = L("Rotate the mesh by this axis before slicing. Use this for an "
+    def->tooltip = L("Axis the mesh is rotated about before slicing. This is the belt "
-                     "isometric (no shear distortion) belt slicing transform. "
+                     "printer's tilt: an isometric (no distortion) rotation that also "
-                     "Mutually exclusive with the per-axis shear/scale controls "
+                     "drives bed rendering and support gravity tilt, and that the g-code "
-                     "in the UI; the pipeline composes them if both are set in JSON.");
+                     "back-transform inverts before the machine-frame shear/scale and remap. "
+                     "X is the typical gantry tilt (belt travels along Y).");
     def->enum_keys_map = &ConfigOptionEnum<BeltRotationAxis>::get_enum_values();
     def->enum_values  = {"none", "x", "y", "z"};
     def->enum_labels  = {L("None"), L("X"), L("Y"), L("Z")};
     def->mode = comAdvanced;
-    def->set_default_value(new ConfigOptionEnum<BeltRotationAxis>(BeltRotationAxis::None));
+    def->set_default_value(new ConfigOptionEnum<BeltRotationAxis>(BeltRotationAxis::X));
 
     def = this->add("belt_slice_rotation_angle", coFloat);
-    def->label = L("Slicing rotation angle");
+    def->label = L("Belt tilt angle");
     def->category = L("Printable space");
-    def->tooltip = L("Magnitude of the slicing rotation, in degrees. Positive values "
+    def->tooltip = L("Tilt angle of the belt surface, in degrees. Most belt printers use "
-                     "rotate counter-clockwise looking down the positive axis.");
+                     "45°. Positive values rotate counter-clockwise looking down the "
+                     "positive tilt axis; the magnitude is also the physical belt tilt "
+                     "used for bed rendering and support gravity.");
     def->sidetext = L("°");
     def->min = -180.;
     def->max = 180.;
     def->mode = comAdvanced;
-    def->set_default_value(new ConfigOptionFloat(0.));
+    def->set_default_value(new ConfigOptionFloat(45.));
 
     def = this->add("belt_slice_rotation_global", coBool);
     def->label = L("Global");
     def->category = L("Printable space");
     def->tooltip = L("Treat the slicing rotation as part of the global forward transform "
                      "that BeltBackTransform inverts before the machine-frame remap. "
-                     "Required for rotation-mode belt printers; mirrors belt_shear_z_global. "
+                     "Required for rotation-mode belt printers. "
                      "Defaults to on because virtually all rotation-mode printers need it.");
     def->mode = comAdvanced;
     def->set_default_value(new ConfigOptionBool(true));
@@ -6553,12 +6450,6 @@ void PrintConfigDef::init_fff_params()
         def->set_default_value(new ConfigOptionEnum<BeltTransformOrder>(BeltTransformOrder::ShearThenScale));
     };
 
-    add_belt_transform_order("belt_mesh_transform_order", "Mesh transform order",
-        "Order in which the mesh shear and scale matrices are composed before slicing. "
-        "'Scale, then shear' applies scale first and then shear (current default). "
-        "'Shear, then scale' applies shear first and then scale. The g-code back-transform "
-        "follows the same order so that it correctly inverts the mesh transform.");
-
     // G-code axis remap with sign
     auto add_belt_remap = [this](const char *key, const char *label, const char *tooltip,
                                   RemapAxis default_axis, ConfigOptionMode mode = comSimple) {
@@ -6599,7 +6490,7 @@ void PrintConfigDef::init_fff_params()
     def->tooltip = L("When enabled, the pre-slice axis remap accounts for each object's bed position. "
                       "Without this, the remap is applied locally around each object's center, so "
                       "objects at different positions don't get a position-dependent contribution. "
-                      "Mirrors the per-axis 'Global' option on belt mesh shears, but for the remap.");
+                      "Mirrors the 'Global' option on the belt slicing rotation, but for the remap.");
     def->mode = comExpert;
     def->set_default_value(new ConfigOptionBool(false));
 
@@ -6609,6 +6500,69 @@ void PrintConfigDef::init_fff_params()
 
     // Machine-frame G-code transforms: applied AFTER back-transform and gcode_remap,
     // before per-axis origin snap.  Maps Cartesian G-code to the printer's physical machine frame.
+    // These shear/scale transforms act on the G-code coordinates (not the mesh) — they are
+    // the belt printer's only shear/scale stage.
+    auto add_belt_shear_mode = [this](const char *key, const char *label, BeltShearMode default_mode,
+                                       ConfigOptionMode mode = comAdvanced) {
+        auto def = this->add(key, coEnum);
+        def->label = L(label);
+        def->category = L("Printable space");
+        def->tooltip = L("Shear function applied to this axis in belt printer mode.");
+        def->enum_keys_map = &ConfigOptionEnum<BeltShearMode>::get_enum_values();
+        def->enum_values  = {"none", "pos_cot", "neg_cot", "pos_tan", "neg_tan"};
+        def->enum_labels  = {L("None"), L("+cot(α)"), L("-cot(α)"), L("+tan(α)"), L("-tan(α)")};
+        def->mode = mode;
+        def->set_default_value(new ConfigOptionEnum<BeltShearMode>(default_mode));
+    };
+    auto add_belt_shear_angle = [this](const char *key, const char *label,
+                                        ConfigOptionMode mode = comAdvanced) {
+        auto def = this->add(key, coFloat);
+        def->label = L(label);
+        def->category = L("Printable space");
+        def->tooltip = L("Angle (degrees) for the shear function on this axis.");
+        def->sidetext = L("°");
+        def->min = 0.1;
+        def->max = 89.9;
+        def->mode = mode;
+        def->set_default_value(new ConfigOptionFloat(45));
+    };
+    auto add_belt_axis_enum = [this](const char *key, const char *label, const char *tooltip,
+                                      BeltAxis default_axis, ConfigOptionMode mode = comAdvanced) {
+        auto def = this->add(key, coEnum);
+        def->label = L(label);
+        def->category = L("Printable space");
+        def->tooltip = L(tooltip);
+        def->enum_keys_map = &ConfigOptionEnum<BeltAxis>::get_enum_values();
+        def->enum_values  = {"x", "y", "z"};
+        def->enum_labels  = {L("X"), L("Y"), L("Z")};
+        def->mode = mode;
+        def->set_default_value(new ConfigOptionEnum<BeltAxis>(default_axis));
+    };
+    auto add_belt_scale_mode = [this](const char *key, const char *label, BeltScaleMode default_mode,
+                                       ConfigOptionMode mode = comAdvanced) {
+        auto def = this->add(key, coEnum);
+        def->label = L(label);
+        def->category = L("Printable space");
+        def->tooltip = L("Scale factor applied to this axis in belt printer mode.");
+        def->enum_keys_map = &ConfigOptionEnum<BeltScaleMode>::get_enum_values();
+        def->enum_values  = {"none", "inv_sin", "inv_cos", "sin", "cos"};
+        def->enum_labels  = {L("None"), L("1/sin(α)"), L("1/cos(α)"), L("sin(α)"), L("cos(α)")};
+        def->mode = mode;
+        def->set_default_value(new ConfigOptionEnum<BeltScaleMode>(default_mode));
+    };
+    auto add_belt_scale_angle = [this](const char *key, const char *label,
+                                        ConfigOptionMode mode = comAdvanced) {
+        auto def = this->add(key, coFloat);
+        def->label = L(label);
+        def->category = L("Printable space");
+        def->tooltip = L("Angle (degrees) for the scale function on this axis.");
+        def->sidetext = L("°");
+        def->min = 0.1;
+        def->max = 89.9;
+        def->mode = mode;
+        def->set_default_value(new ConfigOptionFloat(45));
+    };
+
     add_belt_shear_mode ("gcode_shear_x", "Function", BeltShearMode::None, comExpert);
     add_belt_shear_angle("gcode_shear_x_angle", "Angle", comExpert);
     add_belt_axis_enum  ("gcode_shear_x_from", "From", "Source axis for X shear in the machine-frame stage.", BeltAxis::Z, comExpert);
@@ -6635,19 +6589,6 @@ void PrintConfigDef::init_fff_params()
         "applied to G-code coordinates. 'Scale, then shear' applies scale first and then "
         "shear (current default). 'Shear, then scale' applies shear first and then scale.");
 
-    add_belt_remap("post_gcode_remap_x", "X",
-        "Axis remap in the machine-frame stage. Applied AFTER gcode_remap, "
-        "to put coordinates into the printer's physical axis labelling. Default +X: no change.",
-        RemapAxis::PosX);
-    add_belt_remap("post_gcode_remap_y", "Y",
-        "Axis remap in the machine-frame stage. Applied AFTER gcode_remap, "
-        "to put coordinates into the printer's physical axis labelling. Default +Y: no change.",
-        RemapAxis::PosY);
-    add_belt_remap("post_gcode_remap_z", "Z",
-        "Axis remap in the machine-frame stage. Applied AFTER gcode_remap, "
-        "to put coordinates into the printer's physical axis labelling. Default +Z: no change.",
-        RemapAxis::PosZ);
-
     def = this->add("gcode_back_transform", coBool);
     def->label = L("G-code back-transform");
     def->category = L("Printable space");
@@ -11801,16 +11742,22 @@ Polygons get_bed_excluded_area(const PrintConfig& cfg)
 {
     const Pointfs exclude_area_points = cfg.bed_exclude_area.values;
 
-    // Belt printer: project exclusion zone points from belt surface to machine-frame XY.
+    // Belt printer: project exclusion zone points from the belt surface to machine-frame XY.
-    // On the belt surface, Z=0, so machine_Y = belt_Y * cos(angle).
+    // On the belt surface Z=0, so the in-plane axis foreshortens by cos(tilt).  The tilt
+    // axis decides which bed axis foreshortens: tilt about X (belt along Y) scales Y,
+    // tilt about Y (belt along X) scales X.  Derived from belt_slice_rotation.
     const bool is_belt = cfg.belt_printer.value;
-    const double belt_cos = is_belt ? std::cos(Geometry::deg2rad(cfg.belt_printer_angle.value)) : 1.0;
+    const auto tilt    = BeltTransformPipeline::physical_tilt(
+        cfg.belt_slice_rotation.value, cfg.belt_slice_rotation_angle.value);
+    const double cos_x = is_belt ? std::cos(Geometry::deg2rad(tilt.tilt_x_deg)) : 1.0; // foreshortens Y
+    const double cos_y = is_belt ? std::cos(Geometry::deg2rad(tilt.tilt_y_deg)) : 1.0; // foreshortens X
 
     Polygon exclude_poly;
     for (int i = 0; i < exclude_area_points.size(); i++) {
         auto pt = exclude_area_points[i];
-        double y = is_belt ? pt.y() * belt_cos : pt.y();
+        double x = is_belt ? pt.x() * cos_y : pt.x();
-        exclude_poly.points.emplace_back(scale_(pt.x()), scale_(y));
+        double y = is_belt ? pt.y() * cos_x : pt.y();
+        exclude_poly.points.emplace_back(scale_(x), scale_(y));
     }
 
     exclude_poly.make_counter_clockwise();

src/libslic3r/PrintConfig.hpp

@@ -1573,29 +1573,13 @@ PRINT_CONFIG_CLASS_DERIVED_DEFINE(
     ((ConfigOptionFloat,               build_plate_tilt_y))
     // Belt printer settings (printer-level).
     ((ConfigOptionBool,                belt_printer))
-    ((ConfigOptionFloat,               belt_printer_angle))
     ((ConfigOptionBool,                belt_printer_infinite_y))
-    ((ConfigOptionEnum<BeltShearMode>,  belt_shear_x))
+    // Mesh rotation applied before slicing — the sole mesh-side belt transform and
-    ((ConfigOptionFloat,                belt_shear_x_angle))
+    // the single source of truth for the physical belt tilt (its angle + axis drive
-    ((ConfigOptionEnum<BeltAxis>,       belt_shear_x_from))
+    // bed rendering, support gravity tilt, and the bed-exclusion projection).
-    ((ConfigOptionBool,                 belt_shear_x_global))
+    // Isometric (no distortion); the g-code back-transform inverts it before the
-    ((ConfigOptionEnum<BeltShearMode>,  belt_shear_y))
+    // machine-frame remap.  (Shear & scale are applied to the g-code, not the
-    ((ConfigOptionFloat,                belt_shear_y_angle))
+    // mesh — see gcode_shear_* / gcode_scale_* below.)
-    ((ConfigOptionEnum<BeltAxis>,       belt_shear_y_from))
-    ((ConfigOptionBool,                 belt_shear_y_global))
-    ((ConfigOptionEnum<BeltShearMode>,  belt_shear_z))
-    ((ConfigOptionFloat,                belt_shear_z_angle))
-    ((ConfigOptionEnum<BeltAxis>,       belt_shear_z_from))
-    ((ConfigOptionBool,                 belt_shear_z_global))
-    ((ConfigOptionEnum<BeltScaleMode>,  belt_scale_x))
-    ((ConfigOptionFloat,                belt_scale_x_angle))
-    ((ConfigOptionEnum<BeltScaleMode>,  belt_scale_y))
-    ((ConfigOptionFloat,                belt_scale_y_angle))
-    ((ConfigOptionEnum<BeltScaleMode>,  belt_scale_z))
-    ((ConfigOptionFloat,                belt_scale_z_angle))
-    // Global mesh rotation as an alternative to per-axis shear/scale (isometric
-    // slicing transform).  Composes with shear in the pipeline math; UI gates
-    // them as mutually exclusive.
     ((ConfigOptionEnum<BeltRotationAxis>, belt_slice_rotation))
     ((ConfigOptionFloat,                  belt_slice_rotation_angle))
     ((ConfigOptionBool,                   belt_slice_rotation_global))
@@ -1621,11 +1605,7 @@ PRINT_CONFIG_CLASS_DERIVED_DEFINE(
     ((ConfigOptionFloat,                gcode_scale_y_angle))
     ((ConfigOptionEnum<BeltScaleMode>,  gcode_scale_z))
     ((ConfigOptionFloat,                gcode_scale_z_angle))
-    ((ConfigOptionEnum<BeltTransformOrder>, belt_mesh_transform_order))
     ((ConfigOptionEnum<BeltTransformOrder>, belt_gcode_transform_order))
-    ((ConfigOptionEnum<RemapAxis>,      post_gcode_remap_x))
-    ((ConfigOptionEnum<RemapAxis>,      post_gcode_remap_y))
-    ((ConfigOptionEnum<RemapAxis>,      post_gcode_remap_z))
     ((ConfigOptionBool,                 gcode_back_transform))
     ((ConfigOptionBool,                 belt_preslice_global))
     ((ConfigOptionEnum<FirstLayerPlaneMode>, first_layer_plane))

src/libslic3r/PrintObjectSlice.cpp

@@ -341,9 +341,7 @@ static std::vector<std::vector<ExPolygons>> slices_to_regions(
                 // pushes those layers into the parallel_for path below, which handles multi-volume
                 // clipping per layer without relying on the bbox Z range.
                 const bool bbox_z_in_layer_frame = !(print_config.belt_printer.value &&
-                    (BeltTransformPipeline::has_shear(print_config)
+                    (BeltTransformPipeline::has_rotation(print_config)
-                        || BeltTransformPipeline::has_scale(print_config)
-                        || BeltTransformPipeline::has_rotation(print_config)
                         || BeltTransformPipeline::has_preslice_remap(print_config)));
                 // Belt-transform addendum: with bbox-Z untrusted, the simple path's
                 // "first model_part wins" logic drops subsequent volumes' slices unless
@@ -880,12 +878,12 @@ void groupingVolumesForBrim(PrintObject* object, LayerPtrs& layers, int firstLay
 // Resulting expolygons of layer regions are marked as Internal.
 void PrintObject::slice()
 {
-    BOOST_LOG_TRIVIAL(warning) << "[BELTRACE] slice request tid=" << std::this_thread::get_id() << " obj=" << this;
+    BOOST_LOG_TRIVIAL(trace) << "[BELTRACE] slice request tid=" << std::this_thread::get_id() << " obj=" << this;
     if (! this->set_started(posSlice)) {
-        BOOST_LOG_TRIVIAL(warning) << "[BELTRACE] slice SKIP tid=" << std::this_thread::get_id() << " obj=" << this << " (already started/done)";
+        BOOST_LOG_TRIVIAL(trace) << "[BELTRACE] slice SKIP tid=" << std::this_thread::get_id() << " obj=" << this << " (already started/done)";
         return;
     }
-    BOOST_LOG_TRIVIAL(warning) << "[BELTRACE] slice ENTER tid=" << std::this_thread::get_id() << " obj=" << this;
+    BOOST_LOG_TRIVIAL(trace) << "[BELTRACE] slice ENTER tid=" << std::this_thread::get_id() << " obj=" << this;
     //BBS: add flag to reload scene for shell rendering
     m_print->set_status(5, L("Slicing mesh"), PrintBase::SlicingStatus::RELOAD_SCENE);
     std::vector<coordf_t> layer_height_profile;
@@ -968,16 +966,16 @@ void PrintObject::slice()
     // regardless of global mode, only the output Z coordinates change.
     {
         const auto &pcfg = this->print()->config();
-        BOOST_LOG_TRIVIAL(warning) << "Belt global check: belt_printer=" << pcfg.belt_printer.value
+        BOOST_LOG_TRIVIAL(trace) << "Belt global check: belt_printer=" << pcfg.belt_printer.value
-            << " belt_shear_z=" << int(pcfg.belt_shear_z.value)
+            << " belt_slice_rotation=" << int(pcfg.belt_slice_rotation.value)
-            << " belt_shear_z_global=" << pcfg.belt_shear_z_global.value
+            << " belt_slice_rotation_global=" << pcfg.belt_slice_rotation_global.value
             << " belt_preslice_global=" << pcfg.belt_preslice_global.value
             << " object=" << this->model_object()->name;
         if (pcfg.belt_printer.value) {
 
             Point inst_shift = this->instances().empty() ? Point(0, 0)
                 : this->instances().front().shift - this->center_offset();
-            BOOST_LOG_TRIVIAL(warning) << "Belt global: object " << this->model_object()->name
+            BOOST_LOG_TRIVIAL(trace) << "Belt global: object " << this->model_object()->name
                 << " instances=" << this->instances().size()
                 << " shift=(" << unscale<double>(inst_shift.x()) << ", " << unscale<double>(inst_shift.y()) << ")";
 
@@ -987,20 +985,14 @@ void PrintObject::slice()
             // so the slicer can slice with slicer_z >= 0.  BeltBackTransform inverts
             // build_forward_transform() which DOES NOT include this per-object
             // Z-shift (it's not known until vertex scan time).  Result: G-code
-            // coords emerge offset by the un-undone Z-shift — for shear that's a
+            // coords emerge offset by the un-undone Z-shift — the inverse rotation
-            // pure machine_z lift; for rotation it leaks into both machine_y and
+            // couples slicer_z back into both machine_y and machine_z.  Compensating
-            // machine_z because the inverse rotation couples slicer_z back into
+            // layer.print_z by belt_z_shift here makes the back-transform produce
-            // both axes.  Compensating layer.print_z by shear_min_z here makes the
+            // correct machine-frame coordinates whether or not a global mode is active.
-            // back-transform produce correct machine-frame coordinates whether or
-            // not any global mode is active.
-            //
-            // (The original global-mode-only application of shear_min_z was sized
-            // for cube-vs-inverted-cone-tip differentiation; the same compensation
-            // is what fixes assemblies and rotation-mode parts where z_shift > 0.)
             double belt_surface_z = BeltTransformPipeline::has_preslice_remap(pcfg)
                 ? BeltTransformPipeline::remap_bbox(*this->model_object(), pcfg).min.z() : 0.;
-            double shear_min_z = m_belt_min_z - belt_surface_z;
+            double belt_z_shift = m_belt_min_z - belt_surface_z;
-            double global_z_offset = shear_min_z;
+            double global_z_offset = belt_z_shift;
 
             // Centering correction: trafo_centered pretranslates by
             // -m_center_offset.{x,y}.  Under the belt forward transform, the
@@ -1019,7 +1011,7 @@ void PrintObject::slice()
                             0.);
                 double centering_z_corr = (T_fwd.linear() * c_off).z();
                 global_z_offset += centering_z_corr;
-                BOOST_LOG_TRIVIAL(warning) << "[BELT-DEBUG] centering correction"
+                BOOST_LOG_TRIVIAL(trace) << "[BELT-DEBUG] centering correction"
                     << " obj=" << this->model_object()->name
                     << " m_center_offset_mm=(" << c_off.x() << "," << c_off.y() << ")"
                     << " centering_z_corr=" << centering_z_corr
@@ -1031,7 +1023,7 @@ void PrintObject::slice()
             // print_z adjustment.
             {
                 BoundingBoxf3 raw_bb = this->model_object()->raw_bounding_box();
-                BOOST_LOG_TRIVIAL(warning) << "[BELT-DEBUG] slice() per-object summary"
+                BOOST_LOG_TRIVIAL(trace) << "[BELT-DEBUG] slice() per-object summary"
                     << " obj=" << this->model_object()->name
                     << " n_volumes=" << this->model_object()->volumes.size()
                     << " raw_bbox.min=(" << raw_bb.min.x() << "," << raw_bb.min.y() << "," << raw_bb.min.z() << ")"
@@ -1041,13 +1033,13 @@ void PrintObject::slice()
                     << " inst_shift=(" << unscale<double>(inst_shift.x()) << "," << unscale<double>(inst_shift.y()) << ")"
                     << " m_belt_min_z=" << m_belt_min_z
                     << " belt_surface_z=" << belt_surface_z
-                    << " shear_min_z=" << shear_min_z;
+                    << " belt_z_shift=" << belt_z_shift;
                 // Per-volume bbox + get_matrix translation so order/composition is visible.
                 int vi = 0;
                 for (const ModelVolume *mv : this->model_object()->volumes) {
                     if (!mv->is_model_part()) { ++vi; continue; }
                     BoundingBoxf3 vol_bb = mv->mesh().transformed_bounding_box(mv->get_matrix());
-                    BOOST_LOG_TRIVIAL(warning) << "[BELT-DEBUG]   vol[" << vi
+                    BOOST_LOG_TRIVIAL(trace) << "[BELT-DEBUG]   vol[" << vi
                         << "] id=" << mv->id().id << " name='" << mv->name << "'"
                         << " get_matrix.translation=(" << mv->get_matrix().translation().x() << "," << mv->get_matrix().translation().y() << "," << mv->get_matrix().translation().z() << ")"
                         << " object_bbox.min=(" << vol_bb.min.x() << "," << vol_bb.min.y() << "," << vol_bb.min.z() << ")"
@@ -1063,46 +1055,15 @@ void PrintObject::slice()
                 Vec3d d(unscale<double>(inst_shift.x()), unscale<double>(inst_shift.y()), 0.);
                 Vec3d c = T.linear() * d - d;
                 global_z_offset += c.z();
-                BOOST_LOG_TRIVIAL(warning) << "[BELTRACE] write m_belt_global_xy_correction tid=" << std::this_thread::get_id()
+                BOOST_LOG_TRIVIAL(trace) << "[BELTRACE] write m_belt_global_xy_correction tid=" << std::this_thread::get_id()
                     << " obj=" << this << " old=(" << m_belt_global_xy_correction.x() << "," << m_belt_global_xy_correction.y()
                     << ") new=(" << c.x() << "," << c.y() << ")";
                 m_belt_global_xy_correction = Vec2d(c.x(), c.y());
 
-                BOOST_LOG_TRIVIAL(warning) << "Belt preslice_global: correction=("
+                BOOST_LOG_TRIVIAL(trace) << "Belt preslice_global: correction=("
                     << c.x() << ", " << c.y() << ", " << c.z() << ")"
-                    << " shear_min_z=" << shear_min_z << " (m_belt_min_z=" << m_belt_min_z << ")";
+                    << " belt_z_shift=" << belt_z_shift << " (m_belt_min_z=" << m_belt_min_z << ")";
             } else {
-                struct GAxis { BeltShearMode mode; double angle; int from; bool global; };
-                GAxis gaxes[3] = {
-                    { pcfg.belt_shear_x.value, pcfg.belt_shear_x_angle.value, int(pcfg.belt_shear_x_from.value), pcfg.belt_shear_x_global.value },
-                    { pcfg.belt_shear_y.value, pcfg.belt_shear_y_angle.value, int(pcfg.belt_shear_y_from.value), pcfg.belt_shear_y_global.value },
-                    { pcfg.belt_shear_z.value, pcfg.belt_shear_z_angle.value, int(pcfg.belt_shear_z_from.value), pcfg.belt_shear_z_global.value },
-                };
-
-                // Only the Z-row shear contributes a Z offset from global mode.
-                // (X/Y row shears with global would offset X/Y, not Z — not useful here.)
-                const auto &za = gaxes[2]; // Z row
-                if (za.global && za.mode != BeltShearMode::None && za.from < 2) {
-                    // Use the full forward-transform correction (same formula as
-                    // preslice_global) so the per-bed-position offset matches what
-                    // BeltGCode::on_set_origin's T.linear() pre-multiplication
-                    // expects after back-transform.  The simple `cy*tan(α)` form
-                    // is exact only for ScaleThenShear; under ShearThenScale with
-                    // sy != 1 it leaves the object bottom off the belt plane by
-                    // cy*tan(α)*(sy-1)/sy.
-                    Transform3d T = BeltTransformPipeline::build_forward_transform(pcfg);
-                    Vec3d d(unscale<double>(inst_shift.x()), unscale<double>(inst_shift.y()), 0.);
-                    Vec3d c = T.linear() * d - d;
-                    global_z_offset += c.z();
-                    BOOST_LOG_TRIVIAL(warning) << "[BELTRACE] write m_belt_global_xy_correction tid=" << std::this_thread::get_id()
-                        << " obj=" << this << " old=(" << m_belt_global_xy_correction.x() << "," << m_belt_global_xy_correction.y()
-                        << ") new=(" << c.x() << "," << c.y() << ")";
-                    m_belt_global_xy_correction = Vec2d(c.x(), c.y());
-                    BOOST_LOG_TRIVIAL(warning) << "Belt per-axis Z-shear-global: correction=("
-                        << c.x() << ", " << c.y() << ", " << c.z() << ")"
-                        << " shear_min_z=" << shear_min_z << " (m_belt_min_z=" << m_belt_min_z << ")";
-                }
-
                 // Slicing rotation in global mode: bed-position-dependent Z offset.
                 // For R(α, X): c.z = sin(α)*d.y so objects at different bed-Y
                 // values print at different machine Z values along the inclined belt.
@@ -1129,16 +1090,16 @@ void PrintObject::slice()
                 }
             }
 
-            BOOST_LOG_TRIVIAL(warning) << "Belt global: z_offset=" << global_z_offset
+            BOOST_LOG_TRIVIAL(trace) << "Belt global: z_offset=" << global_z_offset
                 << " (relative to min across " << this->print()->objects().size() << " objects)";
-            BOOST_LOG_TRIVIAL(warning) << "[BELTRACE] write m_belt_global_z_offset tid=" << std::this_thread::get_id()
+            BOOST_LOG_TRIVIAL(trace) << "[BELTRACE] write m_belt_global_z_offset tid=" << std::this_thread::get_id()
                 << " obj=" << this << " old=" << m_belt_global_z_offset << " new=" << global_z_offset;
             m_belt_global_z_offset = global_z_offset;
             // [BELT-DEBUG] Final breakdown of all contributions to layer.print_z
             // and where the first / last layer end up post-adjustment.
-            BOOST_LOG_TRIVIAL(warning) << "[BELT-DEBUG] global_z_offset breakdown"
+            BOOST_LOG_TRIVIAL(trace) << "[BELT-DEBUG] global_z_offset breakdown"
                 << " obj=" << this->model_object()->name
-                << " shear_min_z=" << shear_min_z
+                << " belt_z_shift=" << belt_z_shift
                 << " total_global_z_offset=" << global_z_offset
                 << " xy_correction=(" << m_belt_global_xy_correction.x() << "," << m_belt_global_xy_correction.y() << ")"
                 << " belt_floor_z_shift_before=" << (m_slicing_params.belt_floor_z_shift)
@@ -1152,13 +1113,13 @@ void PrintObject::slice()
                 m_slicing_params.belt_floor_z_shift += global_z_offset;
             }
             if (!m_layers.empty()) {
-                BOOST_LOG_TRIVIAL(warning) << "[BELT-DEBUG]   post-adjustment"
+                BOOST_LOG_TRIVIAL(trace) << "[BELT-DEBUG]   post-adjustment"
                     << " first_layer.print_z=" << m_layers.front()->print_z
                     << " last_layer.print_z=" << m_layers.back()->print_z
                     << " belt_floor_z_shift_after=" << m_slicing_params.belt_floor_z_shift;
             }
             if (!m_layers.empty()) {
-                BOOST_LOG_TRIVIAL(warning) << "Belt global: first_layer_z=" << m_layers.front()->print_z
+                BOOST_LOG_TRIVIAL(trace) << "Belt global: first_layer_z=" << m_layers.front()->print_z
                     << " last_layer_z=" << m_layers.back()->print_z
                     << " num_layers=" << m_layers.size()
                     << " center_offset=(" << unscale<double>(m_center_offset.x())
@@ -1175,7 +1136,7 @@ void PrintObject::slice()
     }
 
     // BBS
-    BOOST_LOG_TRIVIAL(warning) << "[BELTRACE] slice EXIT tid=" << std::this_thread::get_id() << " obj=" << this
+    BOOST_LOG_TRIVIAL(trace) << "[BELTRACE] slice EXIT tid=" << std::this_thread::get_id() << " obj=" << this
         << " layers=" << m_layers.size() << " belt_min_z=" << m_belt_min_z
         << " belt_global_z_offset=" << m_belt_global_z_offset
         << " belt_xy=(" << m_belt_global_xy_correction.x() << "," << m_belt_global_xy_correction.y() << ")";

src/slic3r/GUI/3DBed.cpp

@@ -700,11 +700,11 @@ void Bed3D::render_model(const Transform3d& view_matrix, const Transform3d& proj
             shader->start_using();
             shader->set_uniform("emission_factor", 0.0f);
             Transform3d model_matrix = Geometry::assemble_transform(m_model_offset);
-            // Belt printer: rotate the bed model about X so the belt tilt is visible.
+            // Belt printer: rotate the bed model about the tilt axis so the belt tilt
-            // Negative angle: belt surface tilts downward away from the nozzle.
+            // is visible.  Negative angle: belt surface tilts downward away from the nozzle.
             if (m_is_belt_printer && m_belt_angle > 0.f) {
                 double angle_rad = Geometry::deg2rad(static_cast<double>(m_belt_angle));
-                model_matrix = Eigen::AngleAxisd(-angle_rad, Vec3d::UnitX()) * model_matrix;
+                model_matrix = Eigen::AngleAxisd(-angle_rad, belt_tilt_unit_axis()) * model_matrix;
             }
             shader->set_uniform("volume_world_matrix",  model_matrix);
             shader->set_uniform("view_model_matrix", view_matrix * model_matrix);
@@ -747,12 +747,10 @@ void Bed3D::render_custom(GLCanvas3D& canvas, const Transform3d& view_matrix, co
 void Bed3D::render_gravity_arrow(const Transform3d& view_matrix, const Transform3d& projection_matrix)
 {
     const DynamicPrintConfig& cfg = wxGetApp().preset_bundle->printers.get_edited_preset().config;
+    // build_plate_tilt_{x,y} are kept in sync with the belt tilt (see TabPrinter), so
+    // reading them here covers both belt and non-belt tilted printers.
     double tilt_x_deg = cfg.opt_float("build_plate_tilt_x");
     double tilt_y_deg = cfg.opt_float("build_plate_tilt_y");
-    // Belt printer: auto-derive gravity direction from belt angle if belt mode is active.
-    if (m_is_belt_printer && m_belt_angle > 0.f) {
-        tilt_x_deg = m_belt_angle;
-    }
     if (tilt_x_deg == 0. && tilt_y_deg == 0.) {
         m_gravity_arrow.reset();
         return;
@@ -819,11 +817,12 @@ void Bed3D::render_slicing_arrow(const Transform3d& view_matrix, const Transform
         m_slicing_arrow.init_from(stilized_arrow(16, tip_radius, tip_length, stem_radius, stem_length));
     }
 
-    // The slicing direction: layers stack along the gantry normal.
+    // The slicing direction: layers stack along the gantry normal, i.e. the image of
-    // With mesh rotation R(-alpha, X), the slicing Z-axis in the original frame
+    // +Z under the mesh rotation about the tilt axis.  Use the same AngleAxis as the
-    // points in direction R(+alpha, X) * (0, 0, 1) = (0, -sin(alpha), cos(alpha)).
+    // slicing pipeline so the arrow matches whichever tilt axis is configured.
     double angle_rad = Geometry::deg2rad(static_cast<double>(m_belt_angle));
-    Vec3d slice_dir = Vec3d(0., -std::sin(angle_rad), std::cos(angle_rad)).normalized();
+    Vec3d slice_dir = (Eigen::AngleAxisd(angle_rad, belt_tilt_unit_axis()).toRotationMatrix()
+                       * Vec3d::UnitZ()).normalized();
 
     // Compute rotation to align +Z (arrow default) with slice_dir.
     Vec3d from = Vec3d::UnitZ();
@@ -895,12 +894,12 @@ void Bed3D::render_slicing_plane(const Transform3d& view_matrix, const Transform
     shader->start_using();
 
     // Show a tilted plane representing the slicing direction.
-    // The slicing plane is rotated by belt_angle about X from horizontal.
+    // The slicing plane is rotated by belt_angle about the tilt axis from horizontal.
     // Raise it slightly so it's visible above the bed surface.
     double angle_rad = Geometry::deg2rad(static_cast<double>(m_belt_angle));
     Transform3d model_matrix = Transform3d::Identity();
     model_matrix.translate(Vec3d(0., 0., 30.));
-    model_matrix.rotate(Eigen::AngleAxisd(angle_rad, Vec3d::UnitX()));
+    model_matrix.rotate(Eigen::AngleAxisd(angle_rad, belt_tilt_unit_axis()));
 
     shader->set_uniform("view_model_matrix", view_matrix * model_matrix);
     shader->set_uniform("projection_matrix", projection_matrix);

src/slic3r/GUI/3DBed.hpp

@@ -125,6 +125,8 @@ private:
     // Belt printer state for rendering.
     bool  m_is_belt_printer = false;
     float m_belt_angle = 0.f;
+    // Tilt axis: 0 = X (belt travels along Y, the common case), 1 = Y.
+    int   m_belt_tilt_axis = 0;
 
 public:
     Bed3D() = default;
@@ -146,10 +148,14 @@ public:
     const BuildVolume& build_volume() const { return m_build_volume; }
     BuildVolume& build_volume() { return m_build_volume; }
 
-    // Belt printer bed settings.
+    // Belt printer bed settings.  tilt_axis: 0 = X (belt along Y), 1 = Y.
-    void set_belt_printer(bool enabled, float angle_deg) { m_is_belt_printer = enabled; m_belt_angle = angle_deg; }
+    void set_belt_printer(bool enabled, float angle_deg, int tilt_axis = 0) {
+        m_is_belt_printer = enabled; m_belt_angle = angle_deg; m_belt_tilt_axis = tilt_axis;
+    }
     bool is_belt_printer() const { return m_is_belt_printer; }
     float belt_angle() const { return m_belt_angle; }
+    // Unit vector of the tilt axis in bed space.
+    Vec3d belt_tilt_unit_axis() const { return m_belt_tilt_axis == 1 ? Vec3d::UnitY() : Vec3d::UnitX(); }
 
     // Was the model provided, or was it generated procedurally?
     Type get_type() const { return m_type; }

src/slic3r/GUI/Plater.cpp

@@ -11312,80 +11312,33 @@ void Plater::priv::set_bed_shape(const Pointfs       &shape,
         const auto *belt_opt = config->option<ConfigOptionBool>("belt_printer");
         bool is_belt = belt_opt && belt_opt->value;
         if (is_belt) {
-            double belt_angle = config->opt_float("belt_printer_angle");
+            // The slicing rotation is the single source of truth for the belt tilt:
+            // its magnitude is the physical tilt angle and its axis is the tilt axis.
+            auto rot_axis = config->option<ConfigOptionEnum<BeltRotationAxis>>("belt_slice_rotation")->value;
+            double rot_angle = config->opt_float("belt_slice_rotation_angle");
+            double belt_angle = std::abs(rot_angle);              // physical tilt magnitude
+            int    tilt_axis  = (rot_axis == BeltRotationAxis::Y) ? 1 : 0;
             bool infinite_y = config->opt_bool("belt_printer_infinite_y");
             bed.build_volume().set_belt_printer(true, belt_angle, infinite_y);
-            bed.set_belt_printer(true, static_cast<float>(belt_angle));
+            bed.set_belt_printer(true, static_cast<float>(belt_angle), tilt_axis);
             if (preview)
                 preview->get_canvas3d()->get_gcode_viewer().set_belt_printer(true, static_cast<float>(belt_angle));
 
-            // Compute the inverse of the full belt shear+scale transform for the G-code viewer.
+            // Compute the inverse of the mesh-side belt transform for the G-code
-            auto compute_shear_factor = [](BeltShearMode mode, double angle_deg) -> double {
+            // viewer.  The sole mesh transform is the slicing rotation; build its
-                double angle_rad = Geometry::deg2rad(angle_deg);
+            // matrix from config and hand the viewer its inverse (rotation is
-                double sin_a = std::sin(angle_rad);
+            // orthogonal, so the inverse is the transpose).
-                double cos_a = std::cos(angle_rad);
+            Transform3d forward = Transform3d::Identity();
-                switch (mode) {
+            if (rot_axis != BeltRotationAxis::None && std::abs(rot_angle) > EPSILON) {
-                case BeltShearMode::PosCot: return (sin_a > EPSILON) ?  cos_a / sin_a : 0.;
+                Vec3d unit_axis = Vec3d::UnitX();
-                case BeltShearMode::NegCot: return (sin_a > EPSILON) ? -cos_a / sin_a : 0.;
+                switch (rot_axis) {
-                case BeltShearMode::PosTan: return (cos_a > EPSILON) ?  sin_a / cos_a : 0.;
+                case BeltRotationAxis::X: unit_axis = Vec3d::UnitX(); break;
-                case BeltShearMode::NegTan: return (cos_a > EPSILON) ? -sin_a / cos_a : 0.;
+                case BeltRotationAxis::Y: unit_axis = Vec3d::UnitY(); break;
-                default: return 0.;
+                case BeltRotationAxis::Z: unit_axis = Vec3d::UnitZ(); break;
-                }
+                default: break;
-            };
-            auto compute_scale_factor = [](BeltScaleMode mode, double angle_deg) -> double {
-                if (mode == BeltScaleMode::None) return 1.;
-                double angle_rad = Geometry::deg2rad(angle_deg);
-                double sin_a = std::sin(angle_rad);
-                double cos_a = std::cos(angle_rad);
-                switch (mode) {
-                case BeltScaleMode::InvSin: return (sin_a > EPSILON) ? 1. / sin_a : 1.;
-                case BeltScaleMode::InvCos: return (cos_a > EPSILON) ? 1. / cos_a : 1.;
-                case BeltScaleMode::Sin:    return sin_a;
-                case BeltScaleMode::Cos:    return cos_a;
-                default: return 1.;
-                }
-            };
-
-            // Read shear configs.
-            auto get_shear_mode = [this](const char *key) -> BeltShearMode {
-                auto opt = config->option<ConfigOptionEnum<BeltShearMode>>(key);
-                return opt ? opt->value : BeltShearMode::None;
-            };
-            auto get_axis = [this](const char *key) -> BeltAxis {
-                auto opt = config->option<ConfigOptionEnum<BeltAxis>>(key);
-                return opt ? opt->value : BeltAxis::X;
-            };
-            auto get_scale_mode = [this](const char *key) -> BeltScaleMode {
-                auto opt = config->option<ConfigOptionEnum<BeltScaleMode>>(key);
-                return opt ? opt->value : BeltScaleMode::None;
-            };
-
-            struct AxisShear { BeltShearMode mode; double angle; int from; };
-            AxisShear axes[3] = {
-                { get_shear_mode("belt_shear_x"), config->opt_float("belt_shear_x_angle"), int(get_axis("belt_shear_x_from")) },
-                { get_shear_mode("belt_shear_y"), config->opt_float("belt_shear_y_angle"), int(get_axis("belt_shear_y_from")) },
-                { get_shear_mode("belt_shear_z"), config->opt_float("belt_shear_z_angle"), int(get_axis("belt_shear_z_from")) },
-            };
-
-            Transform3d belt_shear = Transform3d::Identity();
-            for (int row = 0; row < 3; ++row) {
-                if (axes[row].mode != BeltShearMode::None) {
-                    double factor = compute_shear_factor(axes[row].mode, axes[row].angle);
-                    if (std::abs(factor) > EPSILON)
-                        belt_shear.matrix()(row, axes[row].from) += factor;
                 }
+                forward.linear() = Eigen::AngleAxisd(Geometry::deg2rad(rot_angle), unit_axis).toRotationMatrix();
             }
-
-            double sx = compute_scale_factor(get_scale_mode("belt_scale_x"), config->opt_float("belt_scale_x_angle"));
-            double sy = compute_scale_factor(get_scale_mode("belt_scale_y"), config->opt_float("belt_scale_y_angle"));
-            double sz = compute_scale_factor(get_scale_mode("belt_scale_z"), config->opt_float("belt_scale_z_angle"));
-            Transform3d belt_scale = Transform3d::Identity();
-            belt_scale.matrix()(0, 0) = sx;
-            belt_scale.matrix()(1, 1) = sy;
-            belt_scale.matrix()(2, 2) = sz;
-
-            // Forward transform: scale * shear. Inverse for the viewer.
-            Transform3d forward = belt_scale * belt_shear;
             Transform3d inverse = forward.inverse();
             if (preview)
                 preview->get_canvas3d()->get_gcode_viewer().set_belt_inverse_transform(inverse);
@@ -13730,10 +13683,10 @@ void Plater::load_gcode(const wxString& filename)
 
     current_print.set_gcode_file_ready();
 
-    // Belt printer: detect belt_printer_angle from loaded G-code header and enable
+    // Belt printer: detect the belt tilt from the loaded G-code header and enable
     // belt view mode on the GCodeViewer so the "Show designed view" toggle appears.
-    if (current_result->belt_printer_angle > 0.f) {
+    if (current_result->belt_tilt_angle > 0.f) {
-        float angle = current_result->belt_printer_angle;
+        float angle = current_result->belt_tilt_angle;
         p->preview->get_canvas3d()->get_gcode_viewer().set_belt_printer(true, angle);
     } else {
         p->preview->get_canvas3d()->get_gcode_viewer().set_belt_printer(false, 0.f);

src/slic3r/GUI/Tab.cpp

@@ -4,6 +4,7 @@
 #include "PresetHints.hpp"
 #include "libslic3r/PresetBundle.hpp"
 #include "libslic3r/PrintConfig.hpp"
+#include "libslic3r/BeltTransform.hpp"
 #include "libslic3r/Utils.hpp"
 #include "libslic3r/Model.hpp"
 #include "libslic3r/GCode/GCodeProcessor.hpp"
@@ -4464,68 +4465,22 @@ void TabPrinter::build_fff()
         // checkbox is hidden when belt_printer is off (see TabPrinter::toggle_options).
         auto belt_og = page->new_optgroup(L("Belt printer"), L"param_advanced");
         belt_og->append_single_option_line("belt_printer");
-        belt_og->append_single_option_line("belt_printer_angle");
         belt_og->append_single_option_line("belt_printer_infinite_y");
-        // Mesh rotate (default belt-side transform): isometric, no distortion.
+        // Belt tilt: the sole mesh-side transform and the single source of truth for
-        // Shown above the per-axis shear/scale rows because most users should
+        // the physical tilt (drives bed rendering and support gravity tilt too).
-        // pick rotation; shear/scale is the expert escape hatch.
+        // Isometric rotation, no distortion; the back-transform inverts it before the
+        // machine-frame remap.
         {
-            Line line = { L("Mesh rotate"),
+            Line line = { L("Belt tilt"),
-                          L("Global mesh rotation applied before slicing.  Isometric "
+                          L("Belt tilt axis and angle, applied as a mesh rotation before "
-                            "(no distortion); the back-transform inverts it before the "
+                            "slicing.  Also drives bed rendering and support gravity tilt.  "
-                            "machine-frame remap.  Default belt transform.  Mutually "
+                            "Isometric (no distortion); the back-transform inverts it before "
-                            "exclusive with per-axis shear/scale in the UI.") };
+                            "the machine-frame remap.") };
             line.append_option(belt_og->get_option("belt_slice_rotation"));
             line.append_option(belt_og->get_option("belt_slice_rotation_angle"));
             line.append_option(belt_og->get_option("belt_slice_rotation_global"));
             belt_og->append_line(line);
         }
-        // Per-axis shear/scale: expert escape hatch for non-rigid belt transforms
-        // (BlackBelt-style 1/sin scaling, asymmetric belt geometries, etc.).
-        // Group mode + angle + source on one row per axis.
-        {
-            Line line = { L("Mesh shear X"), L("Shear applied to the X axis before slicing") };
-            line.append_option(belt_og->get_option("belt_shear_x"));
-            line.append_option(belt_og->get_option("belt_shear_x_angle"));
-            line.append_option(belt_og->get_option("belt_shear_x_from"));
-            line.append_option(belt_og->get_option("belt_shear_x_global"));
-            belt_og->append_line(line);
-        }
-        {
-            Line line = { L("Mesh shear Y"), L("Shear applied to the Y axis before slicing") };
-            line.append_option(belt_og->get_option("belt_shear_y"));
-            line.append_option(belt_og->get_option("belt_shear_y_angle"));
-            line.append_option(belt_og->get_option("belt_shear_y_from"));
-            line.append_option(belt_og->get_option("belt_shear_y_global"));
-            belt_og->append_line(line);
-        }
-        {
-            Line line = { L("Mesh shear Z"), L("Shear applied to the Z axis before slicing") };
-            line.append_option(belt_og->get_option("belt_shear_z"));
-            line.append_option(belt_og->get_option("belt_shear_z_angle"));
-            line.append_option(belt_og->get_option("belt_shear_z_from"));
-            line.append_option(belt_og->get_option("belt_shear_z_global"));
-            belt_og->append_line(line);
-        }
-        {
-            Line line = { L("Mesh scale X"), L("Scale applied to the X axis before slicing") };
-            line.append_option(belt_og->get_option("belt_scale_x"));
-            line.append_option(belt_og->get_option("belt_scale_x_angle"));
-            belt_og->append_line(line);
-        }
-        {
-            Line line = { L("Mesh scale Y"), L("Scale applied to the Y axis before slicing") };
-            line.append_option(belt_og->get_option("belt_scale_y"));
-            line.append_option(belt_og->get_option("belt_scale_y_angle"));
-            belt_og->append_line(line);
-        }
-        {
-            Line line = { L("Mesh scale Z"), L("Scale applied to the Z axis before slicing") };
-            line.append_option(belt_og->get_option("belt_scale_z"));
-            line.append_option(belt_og->get_option("belt_scale_z_angle"));
-            belt_og->append_line(line);
-        }
-        belt_og->append_single_option_line("belt_mesh_transform_order");
         {
             Line line = { L("Pre-slice axis remap"),
                           L("Remap model axes before slicing so the slicer's coordinate system matches "
@@ -4537,13 +4492,6 @@ void TabPrinter::build_fff()
             line.append_option(belt_og->get_option("preslice_remap_global"));
             belt_og->append_line(line);
         }
-        {
-            Line line = { L("G-code axis remap (post-slice)"), L("Remap slicing-frame axes to machine axes in G-code output. Applied AFTER slicing, during G-code generation.") };
-            line.append_option(belt_og->get_option("gcode_remap_x"));
-            line.append_option(belt_og->get_option("gcode_remap_y"));
-            line.append_option(belt_og->get_option("gcode_remap_z"));
-            belt_og->append_line(line);
-        }
         belt_og->append_single_option_line("belt_preslice_global");
         belt_og->append_single_option_line("gcode_back_transform");
         {
@@ -4588,12 +4536,10 @@ void TabPrinter::build_fff()
         {
             auto mf = page->new_optgroup(L("Machine frame transforms"), L"param_advanced");
             {
-                Line line = { L("Post-gcode axis remap"),
+                Line line = { L("G-code axis remap (post-slice)"), L("Remap slicing-frame axes to machine axes in G-code output. Applied AFTER slicing, during G-code generation.") };
-                              L("Axis remap in the machine-frame stage. Applied AFTER gcode_remap, "
+                line.append_option(mf->get_option("gcode_remap_x"));
-                                "to put coordinates into the printer's physical axis labelling.") };
+                line.append_option(mf->get_option("gcode_remap_y"));
-                line.append_option(mf->get_option("post_gcode_remap_x"));
+                line.append_option(mf->get_option("gcode_remap_z"));
-                line.append_option(mf->get_option("post_gcode_remap_y"));
-                line.append_option(mf->get_option("post_gcode_remap_z"));
                 mf->append_line(line);
             }
             {
@@ -5612,20 +5558,9 @@ void TabPrinter::toggle_options()
         // Belt printer: show belt-specific settings only when belt_printer is enabled.
         bool is_belt = m_config->opt_bool("belt_printer");
         bool expert_or_above = (m_mode >= comExpert);
-        toggle_line("belt_printer_angle", is_belt);
         toggle_line("belt_printer_infinite_y", is_belt);
-        // Mesh rotate: advanced (visible by default in belt mode).
+        // Belt tilt: the sole mesh-side belt transform (visible by default in belt mode).
         toggle_line("belt_slice_rotation", is_belt);
-        // Mesh shear/scale: expert-only (the rigid rotation above is the
-        // primary belt transform; shear/scale is reserved for power users
-        // matching BlackBelt-style 1/sin scale or asymmetric belt geometries).
-        toggle_line("belt_shear_x", is_belt && expert_or_above);
-        toggle_line("belt_shear_y", is_belt && expert_or_above);
-        toggle_line("belt_shear_z", is_belt && expert_or_above);
-        toggle_line("belt_scale_x", is_belt && expert_or_above);
-        toggle_line("belt_scale_y", is_belt && expert_or_above);
-        toggle_line("belt_scale_z", is_belt && expert_or_above);
-        toggle_line("belt_mesh_transform_order", is_belt && expert_or_above);
         for (auto el : {"belt_origin_snap_x", "belt_origin_snap_y", "belt_origin_snap_z"})
             toggle_line(el, is_belt);
 
@@ -5641,59 +5576,11 @@ void TabPrinter::toggle_options()
         // preslice_remap_global: superseded by belt_preslice_global
         toggle_option("preslice_remap_global", is_belt && !belt_global);
 
-        // Mutual exclusion (UI only): slicing rotation and per-axis shear/scale are
+        // Rotation is the only mesh-side belt transform.  Gray out its angle/global
-        // alternatives in the printer panel. The pipeline math composes them; this
+        // sub-options when no rotation axis is selected.
-        // just disables the inactive set so users pick one path or the other.
         auto rot_axis = m_config->option<ConfigOptionEnum<BeltRotationAxis>>("belt_slice_rotation")->value;
-        bool rotation_active = is_belt
+        toggle_option("belt_slice_rotation_angle",  is_belt && rot_axis != BeltRotationAxis::None);
-            && rot_axis != BeltRotationAxis::None
+        toggle_option("belt_slice_rotation_global", is_belt && rot_axis != BeltRotationAxis::None);
-            && std::abs(m_config->opt_float("belt_slice_rotation_angle")) > 1e-9;
-        bool shear_or_scale_active = is_belt && (
-            m_config->option<ConfigOptionEnum<BeltShearMode>>("belt_shear_x")->value != BeltShearMode::None ||
-            m_config->option<ConfigOptionEnum<BeltShearMode>>("belt_shear_y")->value != BeltShearMode::None ||
-            m_config->option<ConfigOptionEnum<BeltShearMode>>("belt_shear_z")->value != BeltShearMode::None ||
-            m_config->option<ConfigOptionEnum<BeltScaleMode>>("belt_scale_x")->value != BeltScaleMode::None ||
-            m_config->option<ConfigOptionEnum<BeltScaleMode>>("belt_scale_y")->value != BeltScaleMode::None ||
-            m_config->option<ConfigOptionEnum<BeltScaleMode>>("belt_scale_z")->value != BeltScaleMode::None);
-        bool allow_shear_scale = !rotation_active;
-        bool allow_rotation    = !shear_or_scale_active;
-
-        // Disable shear/scale mode dropdowns when rotation is active.
-        for (auto el : {"belt_shear_x", "belt_shear_y", "belt_shear_z",
-                        "belt_scale_x", "belt_scale_y", "belt_scale_z",
-                        "belt_mesh_transform_order"})
-            toggle_option(el, is_belt && allow_shear_scale);
-
-        // Disable rotation controls when any shear/scale is active.
-        toggle_option("belt_slice_rotation",        is_belt && allow_rotation);
-        toggle_option("belt_slice_rotation_angle",  is_belt && allow_rotation && rot_axis != BeltRotationAxis::None);
-        toggle_option("belt_slice_rotation_global", is_belt && allow_rotation && rot_axis != BeltRotationAxis::None);
-
-        // Gray out angle/from sub-options when their parent shear/scale mode is None.
-        // Per-axis globals are superseded when belt_preslice_global is on.
-        auto sx = m_config->option<ConfigOptionEnum<BeltShearMode>>("belt_shear_x")->value;
-        toggle_option("belt_shear_x_angle",  is_belt && sx != BeltShearMode::None && allow_shear_scale);
-        toggle_option("belt_shear_x_from",   is_belt && sx != BeltShearMode::None && allow_shear_scale);
-        toggle_option("belt_shear_x_global", is_belt && sx != BeltShearMode::None && !belt_global && allow_shear_scale);
-
-        auto sy = m_config->option<ConfigOptionEnum<BeltShearMode>>("belt_shear_y")->value;
-        toggle_option("belt_shear_y_angle",  is_belt && sy != BeltShearMode::None && allow_shear_scale);
-        toggle_option("belt_shear_y_from",   is_belt && sy != BeltShearMode::None && allow_shear_scale);
-        toggle_option("belt_shear_y_global", is_belt && sy != BeltShearMode::None && !belt_global && allow_shear_scale);
-
-        auto sz = m_config->option<ConfigOptionEnum<BeltShearMode>>("belt_shear_z")->value;
-        toggle_option("belt_shear_z_angle",  is_belt && sz != BeltShearMode::None && allow_shear_scale);
-        toggle_option("belt_shear_z_from",   is_belt && sz != BeltShearMode::None && allow_shear_scale);
-        toggle_option("belt_shear_z_global", is_belt && sz != BeltShearMode::None && !belt_global && allow_shear_scale);
-
-        auto scx = m_config->option<ConfigOptionEnum<BeltScaleMode>>("belt_scale_x")->value;
-        toggle_option("belt_scale_x_angle", is_belt && scx != BeltScaleMode::None && allow_shear_scale);
-
-        auto scy = m_config->option<ConfigOptionEnum<BeltScaleMode>>("belt_scale_y")->value;
-        toggle_option("belt_scale_y_angle", is_belt && scy != BeltScaleMode::None && allow_shear_scale);
-
-        auto scz = m_config->option<ConfigOptionEnum<BeltScaleMode>>("belt_scale_z")->value;
-        toggle_option("belt_scale_z_angle", is_belt && scz != BeltScaleMode::None && allow_shear_scale);
 
         // Machine-frame transforms: shown only in belt mode.
         // Mirror the Advanced/Expert split used for mesh shear/scale.
@@ -5703,8 +5590,7 @@ void TabPrinter::toggle_options()
         toggle_line("gcode_scale_x", is_belt && expert_or_above);
         toggle_line("gcode_scale_y", is_belt);
         toggle_line("gcode_scale_z", is_belt && expert_or_above);
-        for (auto el : {"belt_gcode_transform_order", "post_gcode_remap_x"})
+        toggle_line("belt_gcode_transform_order", is_belt);
-            toggle_line(el, is_belt);
 
         auto gsx = m_config->option<ConfigOptionEnum<BeltShearMode>>("gcode_shear_x")->value;
         toggle_option("gcode_shear_x_angle", is_belt && gsx != BeltShearMode::None);
@@ -5939,21 +5825,29 @@ void TabPrinter::update_fff()
         m_use_silent_mode = m_config->opt_bool("silent_mode");
     }
 
-    // Belt printer: auto-sync build_plate_tilt_x to belt_printer_angle when belt mode is active.
+    // Belt printer: auto-sync build_plate_tilt_{x,y} (which drives support gravity tilt)
-    // When belt mode is off, reset build_plate_tilt_x to 0 if it was set by belt mode.
+    // from the belt slicing rotation, the single source of truth for the physical tilt.
+    // Tilt about X drives tilt_x, tilt about Y drives tilt_y.  When belt mode is off,
+    // reset whichever tilt axis matches a leftover belt value so we don't clobber a
+    // manually-set tilt on a non-belt tilted printer.
     if (m_config->opt_bool("belt_printer")) {
-        double belt_angle = m_config->opt_float("belt_printer_angle");
+        auto rot_axis = m_config->option<ConfigOptionEnum<BeltRotationAxis>>("belt_slice_rotation")->value;
-        if (m_config->opt_float("build_plate_tilt_x") != belt_angle) {
+        const auto tilt = BeltTransformPipeline::physical_tilt(
-            m_config->set_key_value("build_plate_tilt_x", new ConfigOptionFloat(belt_angle));
+            rot_axis, m_config->opt_float("belt_slice_rotation_angle"));
-        }
+        if (m_config->opt_float("build_plate_tilt_x") != tilt.tilt_x_deg)
+            m_config->set_key_value("build_plate_tilt_x", new ConfigOptionFloat(tilt.tilt_x_deg));
+        if (m_config->opt_float("build_plate_tilt_y") != tilt.tilt_y_deg)
+            m_config->set_key_value("build_plate_tilt_y", new ConfigOptionFloat(tilt.tilt_y_deg));
     } else {
-        // Only reset if build_plate_tilt_x matches a typical belt angle (was set by auto-sync).
+        const auto tilt = BeltTransformPipeline::physical_tilt(
-        // Avoid clobbering a manually-set tilt value for non-belt tilted printers.
+            m_config->option<ConfigOptionEnum<BeltRotationAxis>>("belt_slice_rotation")->value,
-        double current_tilt = m_config->opt_float("build_plate_tilt_x");
+            m_config->opt_float("belt_slice_rotation_angle"));
-        double belt_angle = m_config->opt_float("belt_printer_angle");
+        double tx = m_config->opt_float("build_plate_tilt_x");
-        if (current_tilt != 0. && std::abs(current_tilt - belt_angle) < 0.01) {
+        double ty = m_config->opt_float("build_plate_tilt_y");
+        if (tx != 0. && std::abs(tx - tilt.tilt_x_deg) < 0.01)
             m_config->set_key_value("build_plate_tilt_x", new ConfigOptionFloat(0.));
-        }
+        if (ty != 0. && std::abs(ty - tilt.tilt_y_deg) < 0.01)
+            m_config->set_key_value("build_plate_tilt_y", new ConfigOptionFloat(0.));
     }
 
     toggle_options();