ENH: improve mesh boolean

1. Don't use mcut on splitable volumes
2. If MCut fails, try again with CGAL.

Change-Id: I55d352b166633db9e4548b5c9e6913cf931f5f8f
(cherry picked from commit c1bde5358524d2291db6efa584ff072308ed9d20)

src/libslic3r/CSGMesh/ModelToCSGMesh.hpp

@@ -19,7 +19,7 @@ enum ModelParts {
 };
 
 template<class OutIt>
-void model_to_csgmesh(const ModelObject &mo,
+bool model_to_csgmesh(const ModelObject &mo,
                       const Transform3d &trafo, // Applies to all exported parts
                       OutIt              out,   // Output iterator
                       // values of ModelParts OR-ed
@@ -30,6 +30,7 @@ void model_to_csgmesh(const ModelObject &mo,
     bool do_negatives  = parts_to_include & mpartsNegative;
     bool do_drillholes = parts_to_include & mpartsDrillHoles;
     bool do_splits     = parts_to_include & mpartsDoSplits;
+    bool has_splitable_volume = false;
 
     for (const ModelVolume *vol : mo.volumes) {
         if (vol && vol->mesh_ptr() &&
@@ -58,6 +59,7 @@ void model_to_csgmesh(const ModelObject &mo,
                 part_end.stack_operation = CSGStackOp::Pop;
                 *out = std::move(part_end);
                 ++out;
+                has_splitable_volume = true;
             } else {
                 CSGPart part{&(vol->mesh().its),
                              vol->is_model_part() ? CSGType::Union : CSGType::Difference,
@@ -81,6 +83,8 @@ void model_to_csgmesh(const ModelObject &mo,
     //        ++out;
     //    }
     //}
+
+    return has_splitable_volume;
 }
 
 }} // namespace Slic3r::csg

src/slic3r/GUI/GUI_ObjectList.cpp

@@ -2913,7 +2913,7 @@ void ObjectList::boolean()
         new_object->add_instance();
 
     ModelObject* object = (*m_objects)[obj_idxs.front()];
-    TriangleMesh mesh = Plater::combine_mesh_fff(*object, -1);
+    TriangleMesh mesh = Plater::combine_mesh_fff(*object, -1, [this](const std::string& msg) {return wxGetApp().notification_manager()->push_plater_error_notification(msg); });
     ModelVolume* new_volume = new_object->add_volume(mesh);
 
     // BBS: ensure on bed but no need to ensure locate in the center around origin

src/slic3r/GUI/Plater.cpp

@@ -9945,7 +9945,6 @@ void Plater::export_core_3mf()
     export_3mf(path_u8, SaveStrategy::Silence);
 }
 
-#define USE_CGAL_BOOLEAN 0
 // Following lambda generates a combined mesh for export with normals pointing outwards.
 TriangleMesh Plater::combine_mesh_fff(const ModelObject& mo, int instance_id, std::function<void(const std::string&)> notify_func)
 {
@@ -9953,19 +9952,27 @@ TriangleMesh Plater::combine_mesh_fff(const ModelObject& mo, int instance_id, st
 
     std::vector<csg::CSGPart> csgmesh;
     csgmesh.reserve(2 * mo.volumes.size());
-    csg::model_to_csgmesh(mo, Transform3d::Identity(), std::back_inserter(csgmesh),
+    bool has_splitable_volume = csg::model_to_csgmesh(mo, Transform3d::Identity(), std::back_inserter(csgmesh),
         csg::mpartsPositive | csg::mpartsNegative | csg::mpartsDoSplits);
 
     if (csg::check_csgmesh_booleans(Range{ std::begin(csgmesh), std::end(csgmesh) }) == csgmesh.end()) {
         try {
-#if USE_CGAL_BOOLEAN
+            // mcut can't handle splitable positive volumes
-                auto meshPtr = csg::perform_csgmesh_booleans(Range{ std::begin(csgmesh), std::end(csgmesh) });
+            if (!has_splitable_volume) {
-                mesh = MeshBoolean::cgal::cgal_to_triangle_mesh(*meshPtr);
-#else
                 MeshBoolean::mcut::McutMeshPtr meshPtr = csg::perform_csgmesh_booleans_mcut(Range{ std::begin(csgmesh), std::end(csgmesh) });
                 mesh = MeshBoolean::mcut::mcut_to_triangle_mesh(*meshPtr);
-#endif
+                }
-            } catch (...) {}
+            }
+        catch (...) {}
+
+        // if mcut fails, try again with CGAL
+        if (mesh.empty()) {
+            try {
+                auto meshPtr = csg::perform_csgmesh_booleans(Range{ std::begin(csgmesh), std::end(csgmesh) });
+                mesh = MeshBoolean::cgal::cgal_to_triangle_mesh(*meshPtr);
+                }
+            catch (...) {}
+        }
     }
 
     if (mesh.empty()) {