Can't split a polysurface

Hi, I’m trying to split a closed polysurface but I am having an unexpected result. I’m trying to split the surface into 2 pieces using a polyline. When I run split, I am prompted by rhino for the object to split (so I select it and press enter). Next, I select the cutting object (and press enter). I’d expect to now have two separate shells, but rather I get a prompt that says: Creating meshes…2 polysurfaces added to the selection. So the object does not split, if I select it the whole object is selected. Now if I run edge analyze, it tells me that I now have 4 naked edges and no non-manifold edges. BTW - the 4 naked edges are at the position where I would have expected my object to have been split. The upshot is that I can’t seem to split this object and I don’t know why. The object is reported as valid prior to the splitting process and after, so I am not sure why this isn’t working. Any ideas?



Was the polysurface part of a group? If so the net result would be two separate objects that you can’t separately pick until you ungroup them.

OMG - it turns out that somehow the object had become part of a group (although how that happened is unclear). Thank you so much Jim for solving this problem… I was going bonkers!



How do you check if object was part of group?

The object properties tab will tell if you if it’s grouped…and you’ll pick everything else in the group too.