Hi Andras,

It looks like a few of those shapes have a very small and very tightly bent twist in them at the top, here are some shots zooming in:










There is actually a little vertical edge in there, those pieces don't meet up in a single point like they seem to look like at first.

That kind of sharp sudden twist in the surface makes the surface normal shift suddenly by large amounts in direction in that small area of the surface, that kind of thing gives a lot of trouble for offsetting or shelling.

I think those surfaces (I think there are a couple like that) will need to be reconstructed to get a good shell there.


A few other notes on shelling:

MoI's shell function can have difficulty processing surface models made up of multiple pieces into solids unless they have a pretty simple structure, like only 90 degree planes or only surfaces that are all completely smoothly connected to one another.

Other than that shell can work better if you use it on a solid shape rather than on a surface model shape, or also to avoid problems you can try shelling each surface individually to get something to work with, instead of a trying to do a surface made up of several joined pieces.

There was some previous discussion of this problem here:
http://moi3d.com/forum/index.php?webtag=MOI&msg=133.11


Also there have been several fixes to shelling for v2 so you'll want to make sure you are using the v2 beta instead of v1 for shelling stuff.

- Michael