Polysurface to SubD

Rhino Plant Lip

Greetings

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:
https://docs.mcneel.com/rhino/7/help/en-us/index.htm#commands/tosubd.htm

The ToSubD command converts supported object types into SubD objects.
Input
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.
-wim

Wim
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.

Paul

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.
-wim