Off Topic (sort of) LWCAD 3...

 From:  Michael Gibson
1639.2 In reply to 1639.1 
Hi Will, it is definitely an less intensive calculation process working with polygons rather than NURBS. The whole process of calculating a smooth intersection curve between 2 curved surfaces is pretty involved.

I am hoping to support a deeper history function in the future, which should generally allow you to do things like edit shapes and have boolean results update in response to your edits, stuff like that. But I want to make it a very general purpose mechanism that handles all kinds of modeling functions, not something that is just specifically baked into just boolean commands and nothing else.

It will probably take me longer to make that kind of fully general mechanism, but I think it will pay off a lot more in the end.

- Michael