Finish Fixes from Copilot Review (#39)

* fix: restore BuildVolume bounds when toggling belt mode

set_belt_printer() mutated m_bboxf when enabling but never restored
the original extents on disable or when switching infinite_y true->false,
leaving stale max.y/max.z values that broke collision and object_state
checks. Recompute m_bboxf from m_bed_shape + m_max_print_height at the
top of each call, then apply belt-specific adjustments on top.

Addresses Copilot review comment on PR #12998 (BuildVolume.cpp:196).

* chore: drop [BELT-DEBUG] to_machine_coords log to trace

Was emitting at warning level once per 0.2mm Z bucket during every belt
print export, polluting default user logs. Trace level matches the rest
of the belt diagnostics and is silent in production.

Addresses Copilot review comment on PR #12998 (BeltGCodeWriter.cpp:86).

* chore: drop [BELTRACE] make_perimeters/support logs to trace

Eight warning-level traces around make_perimeters and
generate_support_material were emitting on every call/exit during normal
slicing, cluttering default logs. They're concurrency-debug breadcrumbs
not user-facing diagnostics, so drop them to trace.

Addresses Copilot review comment on PR #12998 (PrintObject.cpp:438).

* perf: gate BeltSliceStrategy diagnostic bbox tracking behind compile flag

apply_to_trafo() walked every model vertex twice (once for min_z, once
for per-volume mesh/slicer bboxes) and emitted seven trace logs per
call. The bboxes and logs are diagnostic only; min_z is the load-bearing
output. Wrap the bbox accumulation, logging, and supporting headers in
SLIC3R_BELT_DIAGNOSTIC_LOG so production builds do the bare min_z scan.

Addresses Copilot review comment on PR #12998 (BeltSliceStrategy.cpp:95).

* fix: apply part_cooling_fan_min_pwm to first-layer plane fan crossings

apply_first_layer_plane_fan_eval emitted band-crossing M106 commands
through GCodeWriter::set_fan() without the per-printer PWM floor that
every other set_fan call in CoolingBuffer applies. On printers with a
non-zero part_cooling_fan_min_pwm, fans could fail to spin up at low
requested speeds near the belt surface.

Addresses Copilot review comment on PR #12998 (CoolingBuffer.cpp:1227).

src/libslic3r/BeltGCodeWriter.cpp

@@ -76,7 +76,7 @@ Vec3d BeltGCodeWriter::to_machine_coords(const Vec3d &pos) const
     int z_bucket = static_cast<int>(std::floor(pos.z() * 5.0));  // every 0.2mm
     if (z_bucket != s_last_logged_z) {
         s_last_logged_z = z_bucket;
-        BOOST_LOG_TRIVIAL(warning) << "[BELT-DEBUG] to_machine_coords"
+        BOOST_LOG_TRIVIAL(trace) << "[BELT-DEBUG] to_machine_coords"
             << " slicer_in=(" << pos.x() << "," << pos.y() << "," << pos.z() << ")"
             << " after_back=(" << after_back.x() << "," << after_back.y() << "," << after_back.z() << ")"
             << " after_remap=(" << after_remap.x() << "," << after_remap.y() << "," << after_remap.z() << ")"

src/libslic3r/BeltSliceStrategy.cpp

@@ -2,9 +2,11 @@
 #include "Model.hpp"
 
 #include <boost/log/trivial.hpp>
+#ifdef SLIC3R_BELT_DIAGNOSTIC_LOG
 #include <iomanip>
 #include <sstream>
 #include <thread>
+#endif
 
 namespace Slic3r {
 
@@ -40,7 +42,8 @@ void BeltSliceStrategy::apply_to_trafo(Transform3d &trafo,
     // 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_rotation) {
-        // [BELT-DEBUG] Capture the incoming trafo for diagnostic logging.
+#ifdef SLIC3R_BELT_DIAGNOSTIC_LOG
+        // 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;
         auto log_mat = [](const Matrix3d &m) {
@@ -63,29 +66,41 @@ void BeltSliceStrategy::apply_to_trafo(Transform3d &trafo,
             << " trafo.linear=" << log_mat(trafo_pre_shift.linear())
             << " trafo.translation=" << log_vec3(trafo_pre_shift.translation())
             << " volumes=" << model_volumes.size();
+#endif
 
         double min_z = std::numeric_limits<double>::max();
+#ifdef SLIC3R_BELT_DIAGNOSTIC_LOG
         int vol_idx = 0;
+#endif
         for (const ModelVolume *mv : model_volumes) {
+#ifdef SLIC3R_BELT_DIAGNOSTIC_LOG
             if (!mv->is_model_part()) { ++vol_idx; continue; }
+#else
+            if (!mv->is_model_part()) continue;
+#endif
             Transform3d vol_trafo = trafo * mv->get_matrix();
-            // [BELT-DEBUG] Per-volume bbox in mesh-frame and post-trafo slicer-frame.
             const auto &its = mv->mesh().its;
+#ifdef SLIC3R_BELT_DIAGNOSTIC_LOG
+            // Per-volume bbox in mesh-frame and post-trafo slicer-frame.
             Vec3d mesh_min(std::numeric_limits<double>::max(), std::numeric_limits<double>::max(), std::numeric_limits<double>::max());
             Vec3d mesh_max(std::numeric_limits<double>::lowest(), std::numeric_limits<double>::lowest(), std::numeric_limits<double>::lowest());
             Vec3d slicer_min(std::numeric_limits<double>::max(), std::numeric_limits<double>::max(), std::numeric_limits<double>::max());
             Vec3d slicer_max(std::numeric_limits<double>::lowest(), std::numeric_limits<double>::lowest(), std::numeric_limits<double>::lowest());
             double vol_min_z = std::numeric_limits<double>::max();
+#endif
             for (const stl_vertex &v : its.vertices) {
                 Vec3d vm = v.cast<double>();
+                Vec3d pt = vol_trafo * vm;
+                min_z = std::min(min_z, pt.z());
+#ifdef SLIC3R_BELT_DIAGNOSTIC_LOG
                 mesh_min = mesh_min.cwiseMin(vm);
                 mesh_max = mesh_max.cwiseMax(vm);
-                Vec3d pt = vol_trafo * vm;
                 slicer_min = slicer_min.cwiseMin(pt);
                 slicer_max = slicer_max.cwiseMax(pt);
                 vol_min_z = std::min(vol_min_z, pt.z());
-                min_z = std::min(min_z, pt.z());
+#endif
             }
+#ifdef SLIC3R_BELT_DIAGNOSTIC_LOG
             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)
@@ -93,10 +108,13 @@ void BeltSliceStrategy::apply_to_trafo(Transform3d &trafo,
                 << " slicer_bbox_min=" << log_vec3(slicer_min) << " slicer_bbox_max=" << log_vec3(slicer_max)
                 << " vol_min_z=" << vol_min_z;
             ++vol_idx;
+#endif
         }
         double belt_z_shift_val = (min_z < 0. && min_z != std::numeric_limits<double>::max()) ? -min_z : 0.;
+#ifdef SLIC3R_BELT_DIAGNOSTIC_LOG
         BOOST_LOG_TRIVIAL(trace) << "[BELT-DEBUG] combined min_z=" << min_z
             << " z_shift_val=" << belt_z_shift_val;
+#endif
         if (belt_z_shift_val > 0.) {
             Transform3d z_shift = Transform3d::Identity();
             z_shift.matrix()(2, 3) = belt_z_shift_val;
@@ -104,13 +122,17 @@ 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.;
+#ifdef SLIC3R_BELT_DIAGNOSTIC_LOG
             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;
+#endif
             *out_belt_min_z = new_val;
         }
+#ifdef SLIC3R_BELT_DIAGNOSTIC_LOG
         BOOST_LOG_TRIVIAL(trace) << "[BELT-DEBUG] apply_to_trafo exit"
             << " final_trafo.linear=" << log_mat(trafo.linear())
             << " final_trafo.translation=" << log_vec3(trafo.translation());
+#endif
     }
 }
 

src/libslic3r/BuildVolume.cpp

@@ -182,6 +182,12 @@ void BuildVolume::set_belt_printer(bool enabled, double angle_deg, bool infinite
     m_belt_angle = angle_deg;
     m_belt_infinite_y = infinite_y;
 
+    // Restart from the unmodified bbox each call. Without this, toggling
+    // belt mode off (or switching infinite_y true→false) would leave the
+    // extents inflated and break collision / object_state checks.
+    BoundingBoxf bboxf = get_extents(m_bed_shape);
+    m_bboxf = BoundingBoxf3{ to_3d(bboxf.min, 0.), to_3d(bboxf.max, m_max_print_height) };
+
     if (enabled) {
         if (infinite_y) {
             // Extend the Y bound to a very large value for infinite belt.

src/libslic3r/GCode/CoolingBuffer.cpp

@@ -1091,6 +1091,10 @@ std::string CoolingBuffer::apply_first_layer_plane_fan_eval(
     std::string out;
     out.reserve(gcode.size() + 256);
 
+    // Match the PWM floor applied at every other set_fan call in this file so
+    // band-crossing M106 emissions start the fan reliably at low speeds.
+    const unsigned int part_cooling_fan_min_pwm = static_cast<unsigned int>(std::max(0, m_config.part_cooling_fan_min_pwm.value));
+
     // Track position in slicing-frame mm.  Seed from m_current_pos which the
     // CoolingBuffer keeps up-to-date across layers.
     Vec3d cur_pos_mm(m_current_pos[0], m_current_pos[1], m_current_pos[2]);
@@ -1221,7 +1225,7 @@ std::string CoolingBuffer::apply_first_layer_plane_fan_eval(
                         target_fan = pre_band_main_fan;
                 }
                 if (target_fan != current_main_fan) {
-                    out += GCodeWriter::set_fan(m_config.gcode_flavor, target_fan);
+                    out += GCodeWriter::set_fan(m_config.gcode_flavor, target_fan, part_cooling_fan_min_pwm);
                     current_main_fan = target_fan;
                     m_fan_speed = target_fan;
                     m_current_fan_speed = target_fan;

src/libslic3r/PrintObject.cpp

@@ -427,15 +427,15 @@ std::vector<std::set<int>> PrintObject::detect_extruder_geometric_unprintables()
 // 3) Generates perimeters, gap fills and fill regions (fill regions of type stInternal).
 void PrintObject::make_perimeters()
 {
-    BOOST_LOG_TRIVIAL(warning) << "[BELTRACE] make_perimeters request tid=" << std::this_thread::get_id() << " obj=" << this;
+    BOOST_LOG_TRIVIAL(trace) << "[BELTRACE] make_perimeters request tid=" << std::this_thread::get_id() << " obj=" << this;
     // prerequisites
     this->slice();
 
     if (! this->set_started(posPerimeters)) {
-        BOOST_LOG_TRIVIAL(warning) << "[BELTRACE] make_perimeters SKIP tid=" << std::this_thread::get_id() << " obj=" << this << " (already started/done)";
+        BOOST_LOG_TRIVIAL(trace) << "[BELTRACE] make_perimeters SKIP tid=" << std::this_thread::get_id() << " obj=" << this << " (already started/done)";
         return;
     }
-    BOOST_LOG_TRIVIAL(warning) << "[BELTRACE] make_perimeters ENTER tid=" << std::this_thread::get_id() << " obj=" << this;
+    BOOST_LOG_TRIVIAL(trace) << "[BELTRACE] make_perimeters ENTER tid=" << std::this_thread::get_id() << " obj=" << this;
 
     m_print->set_status(15, L("Generating walls"));
     BOOST_LOG_TRIVIAL(info) << "Generating walls..." << log_memory_info();
@@ -533,7 +533,7 @@ void PrintObject::make_perimeters()
     m_print->throw_if_canceled();
     BOOST_LOG_TRIVIAL(debug) << "Generating perimeters in parallel - end";
 
-    BOOST_LOG_TRIVIAL(warning) << "[BELTRACE] make_perimeters EXIT tid=" << std::this_thread::get_id() << " obj=" << this;
+    BOOST_LOG_TRIVIAL(trace) << "[BELTRACE] make_perimeters EXIT tid=" << std::this_thread::get_id() << " obj=" << this;
     this->set_done(posPerimeters);
 }
 
@@ -829,9 +829,9 @@ void PrintObject::detect_overhangs_for_lift()
 
 void PrintObject::generate_support_material()
 {
-    BOOST_LOG_TRIVIAL(warning) << "[BELTRACE] generate_support_material request tid=" << std::this_thread::get_id() << " obj=" << this;
+    BOOST_LOG_TRIVIAL(trace) << "[BELTRACE] generate_support_material request tid=" << std::this_thread::get_id() << " obj=" << this;
     if (this->set_started(posSupportMaterial)) {
-        BOOST_LOG_TRIVIAL(warning) << "[BELTRACE] generate_support_material ENTER tid=" << std::this_thread::get_id() << " obj=" << this;
+        BOOST_LOG_TRIVIAL(trace) << "[BELTRACE] generate_support_material ENTER tid=" << std::this_thread::get_id() << " obj=" << this;
         this->clear_support_layers();
 
         if(!has_support() && !m_print->get_no_check_flag()) {
@@ -872,10 +872,10 @@ void PrintObject::generate_support_material()
             this->_generate_support_material();
             m_print->throw_if_canceled();
         }
-        BOOST_LOG_TRIVIAL(warning) << "[BELTRACE] generate_support_material EXIT tid=" << std::this_thread::get_id() << " obj=" << this;
+        BOOST_LOG_TRIVIAL(trace) << "[BELTRACE] generate_support_material EXIT tid=" << std::this_thread::get_id() << " obj=" << this;
         this->set_done(posSupportMaterial);
     } else {
-        BOOST_LOG_TRIVIAL(warning) << "[BELTRACE] generate_support_material SKIP tid=" << std::this_thread::get_id() << " obj=" << this << " (already started/done)";
+        BOOST_LOG_TRIVIAL(trace) << "[BELTRACE] generate_support_material SKIP tid=" << std::this_thread::get_id() << " obj=" << this << " (already started/done)";
     }
 }