Trimming removes (actually hides) any region of a surface that is bounded or bisected by a curves-on-surface. Trimming a surface lets you create complex edges and holes in NURBS surfaces. You must create curves-on-surface before you can trim the surface.

Trim a surface

1. Choose Edit NURBS > Trim Tool.
2. Click the surface you want to trim.

   A “trim grid” appears on the surface.

3. Click the regions (defined by curves-on-surface) of the surface you want to keep (you do not need to hold to click multiple regions).

   As you click, regions that will be trimmed away are dotted, and regions that will be kept are solid.

   If you want to change the tool so you click the parts of the surface you want to trim off, open the option box (Edit NURBS > Trim Tool > ) and set Selected State to Discard.

4. Press to trim.
   
   Tip

   A seam can divide a region in two. Make sure when you click a region bisected by the seam that both sides are marked.

Untrim a surface

1. Select the surface or surfaces you want to untim.
2. Choose Edit NURBS > Untrim Surfaces.

   The default is to remove all trims from the surface, restoring it to its original state. To only reverse the most recent trim operation, open the option box (Edit NURBS > Untrim Surfaces > ) and set Untrim to Last.

If you turned on the Shrink Surface option when you trimmed the surface, Untrim cannot restore the original shape of the surface.