"Warp" <war### [at] tagpovrayorg> wrote in message
news:3eb6d6b7@news.povray.org...
>   I know next to nothing about NURBS surfaces, but as far as I understand,
> they are kind of extended bicubic patches (ie. they have everything
> bicubic patches have plus lots of extra control parameters to tune the
> surface shape). Bicubic patches are extremely versatile, but they have
> their limits, which AFAIK NURBS don't have (or at least they have less
> limits).

NURBS are just Non-Uniform Rational B-Splines.  Basically, they ARE bicubic
patches (although the term is usually applied to a "sheet" of patches which
are connected at the seems and of which only the actual corner points, not
the control points, are manipulated).

> necessary) and I think you can represent virtually any surface with them.

Unfortunately, you cannot model every shape with a spline of any type (that
I am aware of).  Just try doing a sphere, and you'll see the problem :)

>   I suppose that if you model your huge scene using NURBS surfaces, you
> could have details equivalent to virtually hundreds of millions of
triangles
> without needing to actually allocate memory for all those triangles.

Unless you're up to incredibly long renders, though, POV-Ray first
tesselates them into triangles.

...Chambers

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