Hi Max,

> I am not confident of success, but I'll try to implement Jos Stam's
> method of calculating the surface exactly.

Ok, but evaluating the subdivision surface exactly does not really solve the problem of conversion of the surface into a different form...

I think what you will end up finding is that regular areas of the mesh will convert quite nicely but that there will be difficulties in the areas of extraordinary vertices.

But I'm looking forward to seeing what you come up with anyway! :)

- Michael