From f3fe37eab387533b5b1c3bf15cea5cd3df648799 Mon Sep 17 00:00:00 2001
From: Noisyfox <timemanager.rick@gmail.com>
Date: Sun, 10 May 2026 23:08:40 +0800
Subject: [PATCH] Remap paint after dovetail cut

---
 src/libslic3r/CutUtils.cpp | 71 +++++++++++++++++++++++++++++++++++++-
 1 file changed, 70 insertions(+), 1 deletion(-)

diff --git a/src/libslic3r/CutUtils.cpp b/src/libslic3r/CutUtils.cpp
index 9fc6f13c2a..fbc4d93c3e 100644
--- a/src/libslic3r/CutUtils.cpp
+++ b/src/libslic3r/CutUtils.cpp
@@ -451,15 +451,23 @@ static void merge_solid_parts_inside_object(ModelObjectPtrs& objects)
     for (ModelObject* mo : objects) {
         TriangleMesh mesh;
         // Merge all SolidPart but not Connectors
+        std::vector<std::optional<TriangleSelector::SavedPainting>> saved_paintings;
         for (const ModelVolume* mv : mo->volumes) {
             if (mv->is_model_part() && !mv->is_cut_connector()) {
                 TriangleMesh m = mv->mesh();
                 m.transform(mv->get_matrix());
                 mesh.merge(m);
+                saved_paintings.emplace_back(mv->save_painting());
+                if (saved_paintings.back()) {
+                    saved_paintings.back()->mesh = std::move(m);
+                }
             }
         }
         if (!mesh.empty()) {
-            ModelVolume* new_volume = mo->add_volume(mesh);
+            ModelVolume* new_volume = mo->add_volume(std::move(mesh));
+            for (const auto& saved_painting : saved_paintings) {
+                new_volume->restore_painting(saved_painting, true);
+            }
             new_volume->name = mo->name;
             // Delete all merged SolidPart but not Connectors
             for (int i = int(mo->volumes.size()) - 2; i >= 0; --i) {
@@ -583,6 +591,11 @@ const ModelObjectPtrs& Cut::perform_with_groove(const Groove& groove, const Tran
     tmp_model.add_object(*cut_mo);
     ModelObject* tmp_object = tmp_model.objects.front();
 
+    // Store source volume id so we could track them back after the cut
+    for (int i = 0; i < cut_mo->volumes.size(); i++) {
+        tmp_object->volumes[i]->cut_info.source_volume = cut_mo->volumes[i]->id();
+    }
+
     auto add_volumes_from_cut = [](ModelObject* object, const ModelObjectCutAttribute attribute, const Model& tmp_model_for_cut) {
         const auto& volumes = tmp_model_for_cut.objects.front()->volumes;
         for (const ModelVolume* volume : volumes)
@@ -603,6 +616,20 @@ const ModelObjectPtrs& Cut::perform_with_groove(const Groove& groove, const Tran
         tmp_model_for_cut.add_object(*cut.perform_with_plane().front());
         assert(!tmp_model_for_cut.objects.empty());
 
+        // Track back the volume id
+        for (const auto v : tmp_model_for_cut.objects.front()->volumes) {
+            auto& src_id = v->cut_info.source_volume;
+            if (src_id.valid()) {
+                // Find the src volume
+                for (const auto volume : object->volumes) {
+                    if (src_id == volume->id()) {
+                        src_id = volume->cut_info.source_volume;
+                        break;
+                    }
+                }
+            }
+        }
+
         object->clear_volumes();
         add_volumes_from_cut(object, add_volumes_attribute, tmp_model_for_cut);
         reset_instance_transformation(object, m_instance);
@@ -663,6 +690,48 @@ const ModelObjectPtrs& Cut::perform_with_groove(const Groove& groove, const Tran
     // this part can be added to the upper object now
     add_volumes_from_cut(upper, ModelObjectCutAttribute::KeepLower, tmp_model_for_cut);
 
+    // Paint volumes
+    if (m_attributes.has(ModelObjectCutAttribute::KeepPaint)) {
+        const auto instance_matrix = cut_mo->instances[m_instance]->get_transformation().get_matrix_no_offset();
+        std::map<ObjectID, std::optional<TriangleSelector::SavedPainting>> saved_paintings;
+        auto get_painting = [&saved_paintings, &cut_mo, &instance_matrix](const ObjectID& volume_id) -> std::optional<TriangleSelector::SavedPainting>& {
+            const auto it = saved_paintings.find(volume_id);
+            if (it != saved_paintings.end()) {
+                return it->second;
+            }
+
+            // Export paintings from volume
+            const auto volume = std::find_if(cut_mo->volumes.begin(), cut_mo->volumes.end(),
+                                             [&volume_id](const ModelVolume* v) { return volume_id == v->id(); });
+
+            std::optional<TriangleSelector::SavedPainting> saved_painting = (*volume)->save_painting();
+            if (saved_painting) {
+                // Transform mesh to cut space (same transform as process_volume_cut applies)
+                const auto volume_matrix = (*volume)->get_matrix();
+                saved_painting->mesh.transform(instance_matrix * volume_matrix, true);
+            }
+
+            saved_paintings.emplace(volume_id, std::move(saved_painting));
+
+            return saved_paintings[volume_id];
+        };
+
+        auto paint_volumes = [&get_painting](const ModelObject* object) {
+            for (const auto volume : object->volumes) {
+                if (volume->cut_info.source_volume.valid()) {
+                    volume->restore_painting(get_painting(volume->cut_info.source_volume));
+                }
+            }
+        };
+
+        if (m_attributes.has(ModelObjectCutAttribute::KeepUpper)) {
+            paint_volumes(upper);
+        }
+        if (m_attributes.has(ModelObjectCutAttribute::KeepLower)) {
+            paint_volumes(lower);
+        }
+    }
+
     ModelObjectPtrs cut_object_ptrs;
 
     if (keep_as_parts) {