Sorry, I meant the "align to shape mesh (oriented bounds)" mode...I'm used to calling it an OOBB (object-aligned bounding box) since in any other non-particle context that's what it's called. Although yes...if you just feed it a soup of shapes it has no way of knowing what is the "right" way to orient along the longest local axis, so you'll get flipping.
There's really not an easy answer to the question...if you're just feeding it arbitrary triangles, we may intuitively be able to see what the "right" way to align a transform should be, but algorithmically it's a tough puzzle to solve.
There's really not an easy answer to the question...if you're just feeding it arbitrary triangles, we may intuitively be able to see what the "right" way to align a transform should be, but algorithmically it's a tough puzzle to solve.