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.
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.
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.