Hi Micha,

> (8) mesh #6
> At Rhino the opening in the middle is complete closed by a
> big artefact, at MOI3D the general shape looks a little bit
> strange at the sides (screenshot).

Are you using a very coarse meshing angle for that particular screenshot result?

When I tried your model at normal mesh densities it was looking fine...

At much coarser mesh densities the kinds of things that you show there are not uncommon and can just be a normal part of getting both a coarse edge boundary and a coarse surface quad density.

Generally something that is curved by quite a bit will look a bit strange when using only a small number of jagged polygons to represent it. Particularly if the interior surface happened to get something like no divisions on it while the edges got one division or something like that.

- Michael