>> Not just the rendering method, but things like different reflection and 
>> lighting models, newer methods of increasing the efficiency of ray 
>> tracing (I posted a link in the pov4 group), etc.
>
> OK. I wasn't aware that any existed, but hey.

The lighting model implemented in POV is about the simplest available, what 
was first used on 3D cards 10 years ago.  Today there are far more accurate 
models used, you must have heard names like Cook-Torrence, Blinn etc, if 
you've never looked outside of POV you wouldn't know they existed.  They 
start to model the microfacets on a surface and produce lighting results 
based on the geometry and physics of the microfacets (eg occlusion, 
self-shadowing etc).  Then there's anisotropic materials like brushed metal, 
where the properties are different depending on which direction the light is 
coming from.

AFAIK POV already uses some clever techniques for speeding up tracing 
complex scenes (try adding 100000 spheres to your ray tracer and compare the 
speed with POV...).  But there are plenty more new techniques out there that 
are certainly worth investigating, some of them quite recent.

> My point is that usually, no matter how closely you look at a POV-Ray 
> isosurface, it will always be beautifully smooth. Every NURBS demo I've 
> ever seen for a GPU has been horribly tesellated with sharp edges 
> everywhere.

NURBS are not isosurfaces though.  What the nVidia demo does is to generate 
the triangle mesh on the fly from the isosurface formula.  So when you zoom 
in, it can create more detail over a small area, and when you zoom out it 
doesn't need so much detail, but of course it needs it over a bigger area. 
It gives the impression that there *are* billions of triangles, but in 
reality it only draws the ones that you can see, small enough that you can't 
tell they are triangles.  Clever eh?  Same way as you can drive for an hour 
around the island on "Test Drive Unlimited", seeing billions of triangles, 
but of course it doesn't try to draw them (or even have them in RAM) all at 
once.

> POV-Ray, of course, gets round this problem by using more sophisticated 
> mathematical techniques than simply projecting flat polygons onto a 2D 
> framebuffer. I've yet to see any GPU attempt this.

GPUs just do it in a different way.  The end result is the same, pixels on 
the screen that match what you would expect from the isosurface formula.

> Mmm, OK. Well my graphics card is only a GeForce 7800 GTX, so I had 
> assumed it would be too under-powered to play it at much about 0.02 FPS.

Nah, on low detail it should certainly be playable.

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