Hi Ronald, yeah if your objects have "self intersections" like that it can pretty much mess up booleans.

There have been some changes in booleans since v2 to fix various other kinds of problems (things like calculating intersections to a tighter tolerance when there are small edges involved in the objects), which for most cases should be an improvement but in this particular case with a kind of messy intersection being involved it's sort of a matter of luck that v2 happened to work at all on it...

> I see you visualized the actual geometry lines, that looks very helpful. How did you do
> that ? I looked for it in the options panel, but can't find any option to enable those.

I think that's a screenshot of your objects imported into Rhino - Rhino usually displays a set of extra isocurves on objects, mainly it's a hold over from Rhino's original wireframe display mode. Currently there isn't any way to turn on that kind of additional wire display in MoI but I do want to add it in as a type of analysis tool in the future at some point. Having them on all the time tends to greatly clutter the display and make it more difficult to see the full surfaces, that's why MoI does not really do that type of display by default.

- Michael