How can Surface.Trim() keep original UV domains?

Rhino Developer
1

I’m using this method of surfaces
https://apidocs.co/apps/rhinocommon/6/M_Rhino_Geometry_Surface_Trim.htm
I wonder if there is a way that all resultant “sub” surfaces can retain original surfaces’s UV domains, much like trimming with a curve “by hand” in the rhino model.
Now the trimmed is “shrunk”

2

You need to do the following:

  • extract the u- and/or v-isocurves that you want to use for trimming (or any other surface curve, does not need to be iso-curves)
  • convert the surface to a Brep
  • use BrepFace.Split(curves) to split the one face of the Brep
  • choose which part to keep of the resulting Brep.

https://developer.rhino3d.com/api/RhinoCommon/html/M_Rhino_Geometry_Surface_IsoCurve.htm

https://developer.rhino3d.com/api/RhinoCommon/html/M_Rhino_Geometry_BrepFace_Split.htm

3

Clear. Thanks!
On this topic, do you happen to know if I can “region union” Brep trims? Kinda like applying another Brep’s trim on a Brep that is already a trimmed surface, and getting only the patch in the overlapped area between the two trims.

4

Not directly. I guess you could get the 2D trim curves of both BReps, use a curve boolean operation on them, then do BrepFace.PushUp(curves) to get the 3D trim curves and go from there, but I’m not sure how practical and robust that would be.

6

Keep in mind that split is going to take a lot longer than trim (split is a physical intersection operation). I’d probably still go the trim route and change the result surfaces domains to what they would be in a split. You can change the domains by using the UV data you use to trim with Surface.SetDomain();

That is of course only if your intent is to trim with the iso’s of the surface.