Nathan Kopp wrote:
> 
> Jerry Anning wrote:
> >
> > BMRT is indeed a true ray tracer.  It does not at any point convert
> > NURBS to triangles. Neither does RenderMan.  For that matter, neither
> > they nor POV convert Beziers to triangle meshes.  POV subdivides Beziers
> > into smaller Bezier patches until they are flat enough to be considered
> > rectangles.
> >
> 
> I must disagree. (I'm guessing, but it is an educated guess.)  I agree that
> BMRT is a true raytracer.  But doing anything with NURBS without converting
> them to triangles is very time consuming.  If it did not convert them to
> triangles, the render time would make it so nobody would use NURBS with BMRT.
> Also, I'd bet that BMRT converts the majority (if not all) of its surfaces into
> triangles before rendering.  I know that RenderMan does, since all scanline
> renders convert all objects into triangles.

I'm not guessing.  They don't.  RenderMan doesn't use simple scanline,
it uses REYES which is somewhat different.  There are reasonably fast
ways to do NURBS without triangulating.  Inquire on
comp.graphics.rendering.renderman and/or comp.graphics.algorithms if you
are curious.

Jerry Anning
cle### [at] dholcom

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