Performance improvements:

Lazy "Place on face" gizmo update.
Caching of MeshObject::raw_mesh_bounding_box() for the object size display.
ModelObject::bounding_box(), raw_mesh_bounding_box(), full_raw_mesh_bounding_box() will not copy the mesh.
TriangleMesh::transformed_bounding_box(const Transform3d &trafo) will not copy the mesh data.
get_options_for_bundle() will not return reference to temp value
is_splittable() calls cheap mesh.has_multiple_patches()

src/libslic3r/BoundingBox.hpp

@@ -32,6 +32,7 @@ public:
         }
         this->defined = (this->min(0) < this->max(0)) && (this->min(1) < this->max(1));
     }
+    void reset() { this->defined = false; this->min = PointClass::Zero(); this->max = PointClass::Zero(); }
     void merge(const PointClass &point);
     void merge(const std::vector<PointClass> &points);
     void merge(const BoundingBoxBase<PointClass> &bb);