> Quote - Sqrt(k * (d - k))

That's a neat simplification! Great.

Quote - I don't have time to try it now, but you might want to make a cylinder in some other tool that has no end caps and uses a lot of small polygons. Maybe triangles would be better than quads, too.

Tried that, didn't change anything. Made a few cylinders in Carrara with tons of quands and / or triangles - still got the punch through.

However, I just realized that the answer may be right in front of me.
The preview image for the surface is already showing some strange things - see the arrows onthe attached image..
I'll try and discover if this is a problem in the algorithm or if Matmatic hit some sort of boundary in one of the components.

Rô

My favourite question is "Why?", my second favourite is "Why not?"