Don't remap paint unless it's the final cut

src/libslic3r/CutUtils.cpp

@@ -14,9 +14,9 @@ namespace Slic3r {
 
 using namespace Geometry;
 
-// Saved painting data for remapping after mesh cutting.
+// Saved painting data for remapping after mesh change.
 struct SavedPainting {
-    indexed_triangle_set                    its;  // Original mesh transformed to cut space
+    indexed_triangle_set                    its;  // Original mesh
     TriangleSelector::TriangleSplittingData supported;
     TriangleSelector::TriangleSplittingData seam;
     TriangleSelector::TriangleSplittingData mmu;
@@ -24,21 +24,24 @@ struct SavedPainting {
 };
 
 // Remap painting data from saved source to a cut result mesh, and set on a volume.
-static void remap_and_set_painting(ModelVolume* vol, const indexed_triangle_set& cut_its,
+static void remap_and_set_painting(ModelVolume* vol, const SavedPainting* saved)
-                                    const SavedPainting& saved)
 {
+    if (!saved) {
+        return;
+    }
+
     auto remap_one = [&](const TriangleSelector::TriangleSplittingData& src_data,
                          FacetsAnnotation& target_facets) {
         if (src_data.bitstream.empty())
             return;
-        auto result = TriangleSelector::remap_painting(saved.its, src_data, cut_its);
+        auto result = TriangleSelector::remap_painting(saved->its, src_data, vol->mesh().its);
         if (!result.bitstream.empty())
             target_facets.set_data(result);
     };
-    remap_one(saved.supported, vol->supported_facets);
+    remap_one(saved->supported, vol->supported_facets);
-    remap_one(saved.seam,      vol->seam_facets);
+    remap_one(saved->seam,      vol->seam_facets);
-    remap_one(saved.mmu,       vol->mmu_segmentation_facets);
+    remap_one(saved->mmu,       vol->mmu_segmentation_facets);
-    remap_one(saved.fuzzy,     vol->fuzzy_skin_facets);
+    remap_one(saved->fuzzy,     vol->fuzzy_skin_facets);
 }
 
 static void apply_tolerance(ModelVolume* vol)
@@ -217,28 +220,26 @@ static void process_solid_part_cut(ModelVolume* volume, const Transform3d& insta
     // Add required cut parts to the objects
 
     if (attributes.has(ModelObjectCutAttribute::KeepAsParts)) {
-        add_cut_volume(upper_mesh, upper, volume, cut_matrix, "_A");
+        if (!upper_mesh.empty()) {
-        if (saved_painting && !upper_mesh.empty())
+            add_cut_volume(upper_mesh, upper, volume, cut_matrix, "_A");
-            remap_and_set_painting(upper->volumes.back(), upper_mesh.its, *saved_painting);
+            remap_and_set_painting(upper->volumes.back(), saved_painting);
+        }
         if (!lower_mesh.empty()) {
             add_cut_volume(lower_mesh, upper, volume, cut_matrix, "_B");
-            if (saved_painting)
-                remap_and_set_painting(upper->volumes.back(), lower_mesh.its, *saved_painting);
             upper->volumes.back()->cut_info.is_from_upper = false;
+            remap_and_set_painting(upper->volumes.back(), saved_painting);
         }
         return;
     }
 
-    if (attributes.has(ModelObjectCutAttribute::KeepUpper)) {
+    if (attributes.has(ModelObjectCutAttribute::KeepUpper) && !upper_mesh.empty()) {
         add_cut_volume(upper_mesh, upper, volume, cut_matrix);
-        if (saved_painting && !upper_mesh.empty())
+        remap_and_set_painting(upper->volumes.back(), saved_painting);
-            remap_and_set_painting(upper->volumes.back(), upper_mesh.its, *saved_painting);
     }
 
     if (attributes.has(ModelObjectCutAttribute::KeepLower) && !lower_mesh.empty()) {
         add_cut_volume(lower_mesh, lower, volume, cut_matrix);
-        if (saved_painting)
+        remap_and_set_painting(lower->volumes.back(), saved_painting);
-            remap_and_set_painting(lower->volumes.back(), lower_mesh.its, *saved_painting);
     }
 }
 
@@ -363,21 +364,19 @@ const ModelObjectPtrs& Cut::perform_with_plane()
         // Save painting data before reset_extra_facets() discards it.
         // Only for model parts that will be cut (not modifiers/connectors).
         std::optional<SavedPainting> saved_painting;
-        if (volume->is_model_part() && !volume->mesh().empty()) {
+        if (m_attributes.has(ModelObjectCutAttribute::KeepPaint) && volume->is_any_painted() && volume->is_model_part() && !volume->mesh().empty()) {
-            SavedPainting sp;
             // Get mesh in cut space (same transform as process_volume_cut applies)
             TriangleMesh mesh(volume->mesh());
             const auto volume_matrix = volume->get_matrix();
             mesh.transform(inverse_cut_matrix * instance_matrix * volume_matrix, true);
             mesh.transform(m_cut_matrix);
+            SavedPainting sp;
             sp.its = std::move(mesh.its);
             sp.supported = volume->supported_facets.get_data();
             sp.seam      = volume->seam_facets.get_data();
             sp.mmu       = volume->mmu_segmentation_facets.get_data();
             sp.fuzzy     = volume->fuzzy_skin_facets.get_data();
-            if (!sp.supported.bitstream.empty() || !sp.seam.bitstream.empty() ||
+            saved_painting = std::move(sp);
-                !sp.mmu.bitstream.empty() || !sp.fuzzy.bitstream.empty())
-                saved_painting = std::move(sp);
         }
 
         volume->reset_extra_facets();

src/libslic3r/CutUtils.hpp

@@ -11,7 +11,7 @@ namespace Slic3r {
 
 using ModelObjectPtrs = std::vector<ModelObject*>;
 
-enum class ModelObjectCutAttribute : int { KeepUpper, KeepLower, KeepAsParts, FlipUpper, FlipLower, PlaceOnCutUpper, PlaceOnCutLower, CreateDowels, InvalidateCutInfo };
+enum class ModelObjectCutAttribute : int { KeepUpper, KeepLower, KeepAsParts, FlipUpper, FlipLower, PlaceOnCutUpper, PlaceOnCutLower, CreateDowels, InvalidateCutInfo, KeepPaint };
 using ModelObjectCutAttributes = enum_bitmask<ModelObjectCutAttribute>;
 ENABLE_ENUM_BITMASK_OPERATORS(ModelObjectCutAttribute);
 

src/libslic3r/Model.hpp

@@ -1005,6 +1005,7 @@ public:
     bool is_seam_painted() const { return !this->seam_facets.empty(); }
     bool is_mm_painted() const { return !this->mmu_segmentation_facets.empty(); }
     bool is_fuzzy_skin_painted() const { return !this->fuzzy_skin_facets.empty(); }
+    bool is_any_painted() const { return is_fdm_support_painted() || is_seam_painted() || is_mm_painted() || is_fuzzy_skin_painted(); }
     
     // Orca: Implement prusa's filament shrink compensation approach
     // Returns 0-based indices of extruders painted by multi-material painting gizmo.

src/slic3r/GUI/Gizmos/GLGizmoCut.cpp

@@ -3329,7 +3329,8 @@ void GLGizmoCut3D::perform_cut(const Selection& selection)
                                               only_if(m_rotate_upper, ModelObjectCutAttribute::FlipUpper) |
                                               only_if(m_rotate_lower, ModelObjectCutAttribute::FlipLower) |
                                               only_if(dowels_count > 0, ModelObjectCutAttribute::CreateDowels) |
-                                              only_if(!has_connectors && !cut_with_groove && cut_mo->cut_id.id().invalid(), ModelObjectCutAttribute::InvalidateCutInfo);
+                                              only_if(!has_connectors && !cut_with_groove && cut_mo->cut_id.id().invalid(), ModelObjectCutAttribute::InvalidateCutInfo) |
+                                              ModelObjectCutAttribute::KeepPaint;
 
         // update cut_id for the cut object in respect to the attributes
         update_object_cut_id(cut_mo->cut_id, attributes, dowels_count);