Hi mir4ea, that's a great overview!

One other command that is generally related is "ShrinkTrimmedSrf":
http://moi3d.com/2.0/docs/moi_command_reference10.htm#shrinktrimmedsrf

It shrinks down underlying surfaces, until they are just big enough to hold the trim curves. Sometimes that is useful if you have trimmed away a large area of a large detailed surface for example and only have a small fragment left, by default the whole original surface will still be underneath everything but when you do ShrinkTrimmedSrf it will shrink it down and only keep the area around the current active area. Then you will get a different result when you do an "untrim" afterwards.


This whole overall mechanism of having "underlying surfaces" and trim curves is what makes NURBS modeling very different from polygon modeling, and it's also why NURBS modeling works well with boolean operations, because when you do repeated booleans onto a NURBS object, the original surfaces stay all the same and only new trim curves get created or modified, it helps keep the original surface structure to stay simple. With polygon modeling when you try to do booleans it fractures things into more and more polygons which builds up complexity on each cut.


- Michael