Thanks for the very detailed reply. Evaluating NURBS is useful, but you piqued my interested in the reverse operation. For a moment I almost had the impression we could specify CSG operations based on features extracted from the BREP reconstruction (that would be a game-changer!).

I was looking up at the current docs for the csg->brep conversion, but I don't really see much. Does brlcad actually allow to fit/reconstruct NURBS over the constructed geometry? The export docs still mention IGES export is just faceted.

I'm mostly using openscad and cgal directly, and my experience with both is that model regeneration takes a nosedive for anything non trivial. openscad for example doesn't offer any tool to shoot/analyze rays. The realtime preview also suffers for coplanar z-fighting issues, often making exact CSG operation really hard to debug. However the ergonomics are pretty decent when iterating and constructing geometry on the fly.

Can I ask your role in brl-cad? All your posts are extremely detailed. Are you a contributor? I wonder if I should reinvest time in brl-cad once again.