Fix assembly parts omitted by height range modifiers (#15225)

src/libslic3r/PresetBundle.cpp

@@ -5378,7 +5378,7 @@ void PresetBundle::update_multi_material_filament_presets(size_t to_delete_filam
         f_multiplier.resize(nozzle_nums, 1.f);
     }
 
-    if ( (num_filaments * num_filaments) != size_t(old_matrix.size() / old_nozzle_nums) ) {
+    if (old_matrix.size() != num_filaments * num_filaments * nozzle_nums) {
         // First verify if purging volumes presets for each extruder matches number of extruders
         std::vector<double>& filaments = this->project_config.option<ConfigOptionFloats>("flush_volumes_vector")->values;
         while (filaments.size() < 2* num_filaments) {

src/libslic3r/PrintApply.cpp

@@ -559,9 +559,11 @@ static inline bool model_volume_solid_or_modifier(const ModelVolume &mv)
 
 static inline Transform3f trafo_for_bbox(const Transform3d &object_trafo, const Transform3d &volume_trafo)
 {
-    Transform3d m = object_trafo * volume_trafo;
-    m.translation().x() = 0.;
-    m.translation().y() = 0.;
+    // Orca: Keep the volume's local XY offset for multipart overlap checks, but remove the object's bed placement.
+    Transform3d object_trafo_local = object_trafo;
+    object_trafo_local.translation().x() = 0.;
+    object_trafo_local.translation().y() = 0.;
+    Transform3d m = object_trafo_local * volume_trafo;
     return m.cast<float>();
 }