Michael Smith wrote:
> Possibly. Not knowing much about NURBS mathematically, I couldn't say
> for sure, but doing this tends to be computationally prohibitive - you
> can tesselate enough that you can't tell the difference and still be a
> hell of alot faster than direct intersection tests, in many cases. This
> is presumably why POV uses a tesselated form for the current bezier
> patches.

Yes, that's true.  Doing an actual intersection with spheres, boxes, and other
such polygons is one thing, but bicubic surfaces (uniform or non-uniform) is
really, really slow.  Tesselating during parsing increases parse time, but
produces overall savings in total render time.

I have NURBS 2D curve code and it should be easy to convert it into 3D stuff. 
I actually started working on a NURBS patch for POV about a year ago, but then
when I saw how difficult trimmed NURBS would be, I stopped.  I'm working on
some other POV improvements (uv mapping) currently, but I'd be happy to help if
someone else wants to work on this.

-Nathan

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