Here are some hints for using the Surface surface trimming, Trim, Surface/Surface intersection and Untrim operations.
· Do NOT include portions of the boundary when constructing curves for trimming. Trimming curves may cross or end on boundaries.
· Do not use surface/surface intersection to get a boundary of a surface. Use surface boundary extraction.
· Intersecting tangent surfaces produces inaccurate or broken intersection curves, such as a fillet surface and the surface it's tangent to. Instead, extract curves and trim with a curve instead.
· Do not intersect coincident surfaces (surfaces that overlap). Extract curves and trim with a curve instead.
· Avoid cutting through the pole of a surface with a degeneracy such as the tip of a sphere or surface of revolution.
· Avoid cutting along (across is OK) a seam of a surface. A seam exists, for example, at the left/right boundary of a cylinder. You can detect seams with the curve extraction dialog box, and then canceling out after you know where the seam is. Cutting a seam usually can be avoided by rotating the object.
· Surfaces can be trimmed multiple times.
· Curves for surface/curve trimming can extend off of the surface and/or cut the surface multiple times.