Adding control points to a triangular surface


#1

I’m trying to add control points to a triangular surface through the rebuild command but it always makes a rectangular grid that stretches past the surface. How can I add more control points to a triangular surface without this happening?


(Pascal Golay) #2

Hi Daniel - you can’t always - see the NURBS topology section in https://www.rhino3d.com/download/rhino/5.0/Rhino5Level2Training/

for some information about how surfaces are structured. Depending on the shape, you may be able to construct it in a way that allows you to do what you want - post the object in a 3dm file and someone will take a look.

-Pascal


#3

Hi @Daniel_Csank , It depends on the underlying construction of the surface.
It sounds asif the surface you describe is a trimmed surface so the trimmed part (viewable) can have control points added by

  1. Duplicating the current border of the triangle.
  2. Untrim the surface
  3. Rebuild the surface
  4. Trim the surface using the border which you duplicated in step 1

You could also re-create the surface as a non-trimmed surface from scratch by:
1.Duplicating the 2x adjacent edges on the smaller angle corner.
2. Rebuild the individual curves on each side with the number of control points you want.
3. Loft between the 2 x curves using the Straight option.
If you select the surface now and press F10 you will see that the surface is now an un-trimmed surface.
Michael VS


(David Cockey) #4

The Retrim option in Rebuild will trim the rebuilt surface without need to separately duplicate the boundaries, etc.

This may not result in an exact duplicate of the trimmed surface depending on the shape of the trimmed surface.