RemoveFromGroup changes geometry

I stumbled over a most unusual Rhino behavior. In the attached file, there is a surface object in a one-object group. It is a rather distorted surface, but a valid one. When I use the “RemoveFromGroup” command with “Copy” set to yes, I receive a polysurface.
Why is RemoveFromGroup fiddling around with the geometry at all? Interestingly, the ordinary “Copy” command works just fine, as does RemoveFromGroup without copy. It’s just the combination that seems to freak out Rhino.


130730_RemoveFromGroup_Error.3dm(198.9 KB)

Hi Hanno - the end of the surface where there should be a singularity is not in fact a singularity- if you SetPt, X,Y,Z of the 70 points that are at this location to make them truly coincident, then the object does not split up. Apparently there are some creases in the surface in this area, but a) I could not find them yet- the object is very large (in units) so that may come into play, and b) it should not matter- RemoveFromGroup seems to be sending the object through the ‘kink splitter’ routine that is usual when a surface is added to the file but that seems incorrect in this case to me at least, So I call it a bug- thanks for the report.


Hi Pascal, thanks for the answer. You are right about the surface, but - as you said - the main point is that the geometry shouldn’t be touched at all, so thanks for the bug approval.