news:3fe51ea3$1@news.povray.org...
> all of these changes and renders building this model in any other program
> would require major rebuilds for each change. But with POVRay to move the
> spicket's I just change one variable and rerender. This is the very power
of
> the SDL. Changes could be made with out rebuilding the whole model over
for
> each change.

The possibility to parametrize an object is certainly a big strength of the
SDL. Two things, however:
1) it's reserved for what you can code by yourself with the SDL only, i.e.
without an external modeller. As, we know, this is a lot and some projects
certainly can be done like this (I also know of an entire, real-life,
architectural project coded in SDL rather than with 3D Studio). But it's
also limited, if only by the amount of time you can dedicate to it.

2) let's not assume that this isn't possible in other software. Actually, in
the one I'm learning now, the user has access to the model geometry and can
parametrize them if necessary, make calculations etc.

> They are always IIRC converted to polygons before rendering. So to
> convert NURBS and out put to POVRay is not a handicap for POVRay.
> In fact POVRay handles triangles from NURBS better than most rendering
engines.

As a Rhino user I can tell that having to convert NURBS into POV-Ray is a
handicap. One has to go through the entire model and fine-tune each part so
that the whole thing doesn't end up in a 500 Mb mesh. UV mapping is often
lost in the process, so it's necessary to remap the parts. And of course, a
downsized polygonal mesh is less nice-looking than a native NURBS (or any
other parametric surface in fact).

> And on a side note there is not IIRC a rendering engine that renders NURBS
> directly.

Not all of them certainly, but some do:
Mental Ray
http://www.mentalimages.com/2_1_1_technical/index.html
Renderman
https://renderman.pixar.com/products/tools/renderman.html
Mantra
http://www.sidefx.com/products/houdini/mantra/

Of course, how it's done internally is another problem, but the idea is
still that you feed the renderer a parametric object and that it renders
something nice and smooth and not a bunch of polys.

In any case, NURBS was just an example among others and I'm not specifically
advocating NURBS support in POV-Ray. See the FBX interchange file format,
which gives an idea of what is expected in terms of compatibility :
http://www.kaydara.com/products/fbx/index.php?filename=techspecs


G.

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