Method get_face_sources

tools/Boolean/CSGTree.h:33–35

        virtual void compute_difference() =0;
        virtual void compute_symmetric_difference() =0;
        virtual VectorI get_face_sources() const {
            return VectorI::Zero(0);
        };
        virtual VectorI get_mesh_sources() const {
            return VectorI::Zero(0);
        }