Polysurface to SubD

Rhino Plant Lip


Can someone tell me why I get the results I did converting a Nurbs object to a SubD?

Also why is it that when you convert to SubD and then take the SubD and convert to nurbs the resulting object is not the same a the original polysurface.

Hi Paul -

I - kind of - already answered that in your other thread. I then wrote “You can’t (or not really) create a SubD object from a polysurface.”

More complete information from the help file:

The ToSubD command converts supported object types into SubD objects.
Mesh, Extrusion, Surface, Sub-surface

Polysurfaces are not eligible inputs for the ToSubD command.

Also from the help file:

  • Trims of a surface or sub-surface will be lost in the SubD.
  • Sub-surfaces of a polysurface will be converted individually.

So, unless all sub-surfaces of your polysurface are untrimmed, the individual SubD objects won’t be the same as the original and thus the ToNURBS version thereof won’t be the same of that original.

Thanks for the Lesson. I’m completely new to sub D and working with meshes.

So I’m guessing I have to mesh the nurbs object and then convert it to subD first.

I’ve got a steep learning curve ahead of me. I appreciate your help.


Is there a feature request for this? Or do we just need to explode and ToSubD individual surfaces until then?

Hi Jonathan -

You don’t need to explode a polysurface to be able to run ToSubD on it. You won’t be able to preselect and you need to select all individual surfaces - either by selecting one-by-one or with a window selection.

Apart from that, only in very few and special cases will the result of this operation on a polysurface give you something that is useful.