Hi PaQ,

> Can you confirm that's 100% modo bug ?

Well, the first thing is to see if it's a poly normal flipped problem or if it is a n-gon triangulation problem.

Maybe try deleting the back half of the object - then when you rotate around to the other side do you see those n-gons or are they still missing when viewed from either side? If missing on either side then it's a triangulation problem.

Then the other thing that I'd do is to move some points around on one of the bad n-gons and see if there are any surprises in there like points stacked up where you wouldn't expect possibly making a small self-intersection area or something like that.

Is there any way in Modo to display which point is the starting point in the list of vertices in an n-gon? Modo and LightWave are sensitive to which point is set as the starting point because they determine front face/back face by only looking at the directions of the edges from that first point, so if that first point is in a degenerate area that could be a problem. The double-flip method also sets the first point of the n-gon to a spot that it thinks is good.

I'll take a look at it some too.

- Michael