virtual void after_split_face (Face_handle /* old_face */,
Face_handle new_face, bool )
{
// Assign index to the new face.
new_face->set_data (n_faces);
n_faces++;
}
/*! Create a face f that matches the overlapping region between f1 and f2. */
virtual void create_face(Face_const_handle f1, Face_const_handle f2,
Face_handle f) const
{ f->set_data(f1->data() + f2->data()); }