detaches a half-free point from its carrier (line, segment, plane, sphere,
point). If the point drives a locus-line or -surface, it cannot be detached. To detach it, the locus
must be deleted first.
The unattach-button detaches a half-free point from its carrier (line, segment, plane, sphere,
point). If the point drives a locus-line or -surface, it cannot be detached. To detach it, the locus
must be deleted first.