BindingGroup old_bind_to = bind_to;
bind_peers.shatter(bg1, bg2, triangles);
old_bind_to.shatter(bg2.other(), bg1.other(), triangles);
BindingGroup old_bind_to = bind_to;
bind_peers.shatter(bg1, bg2, triangles);
old_bind_to.shatter(bg2.other(), bg1.other(), triangles);