Hi Alexander,

> It seems to take forever to calculate and then jumbles everthing up.

Usually a result like that means that one of your surfaces may be bunched up and sort of folding back over top of itself in a small area.

The way shelling and offsetting work, they produce a result that follows the surface normal a distance away from the original surface.

But if your surface folds back over top of itself, that means the surface normal (the perpendicular coming off of the surface) jumps around wildly in that area, which interferes with getting a good surface offset calculated from it.

That's just some general stuff to look for, I haven't checked out your model yet but I will take a look at it now.

- Michael