OK. Time for my next challenge. I need to tell the outside of the face from the inside of a face that is part of a body. I was hoping that normals would tell me. Sometimes they point inside the body and sometimes outside. My parts that I am working with are always have a planar "bottom" face and I could tell from that which side of the face is inside. I am certain that with enough thought and the right algorithm I could follow all the faces somehow.

I am thinking that SolidWorks has this built in somehow.

I have looked at IFace2, ISurface, IBody2 and I don't see anything obvious there.

I have combinations of every kind of shape of face - planar, circular, spline, etc.