Hi armin, I've been looking extensively into this boolean problem you reported here on this handle model.

I tracked it down to a change about a year ago in MoI v2 where when it loads a 3DM file, it detects whether surfaces in the model are pieces of an exact cylinder, cone, or sphere and if so it creates a special analytic surface class for that surface instead of having it as a regular generic NURBS surface.

The main difference with the analytic surfaces is that surface/surface intersection with them will do some special cases for them to get a more simple and precise intersection result. That's the idea anyway, but there are some bugs in some particular cases of the analytic surface intersections and that's what was causing this boolean failure.

For now I've disabled the analytic intersection for these problem cases so that it will use the general purpose intersector which then lets this boolean work fine.

I've reported these analytic intersection problems to the authors of the geometry library and I'll probably be able to re-enable them in v3 when they get fixed.

But anyway, your handle boolean will work in the next v2 beta, thanks for reporting the bug.

- Michael