Nonmanifold ToNURBS

Hi All
I’m not sure if this is a bug, limitation, feature or something else, but i just realised, that you can make hollow solids in subD using OffsetSubD - probably due to them being mesh-based. What’s more interesting, is that it carries over when using the ToNURBS command, meaning that you actually get a valid, closed polysurface, but with two disjoint shells. Clipping planes even show them correctly and it’s not tagged as a bad object.

If you explode and re-join, it “correctly” becomes two closed polysurfaces.
I don’t know if this “feature” ought to be changed, since Rhino usually don’t allow this type of geometry to be created.

Hi Jakob -

This feature won’t be changed, no.
FWIW, you can create those objects with regular NURBS as well by first running NonmanifoldMerge, followed by CreateRegions, and then deleting the object in the center.

Cool - never used that one before! :+1: Thanks @wim!