Saul Luizaga <sau### [at] netscapenet> wrote:
> Chambers wrote:
> > The problem is that GPUs, in their current form, are great for 
> > processing triangles but not much else.

> I have to desagree, Ihave seen examples on some web pages how the GPU 
> beat the crap out of a CPU (FPU included) on certain calculations, I was 
> reading about "GPUs as a powerful co-processor" or something like that. 
> Those calculations were prety complex for 3D geometry solving and other 
> stuff I don't recall well, was like a year or so ago.

  The GPU can only be used to your advantage if you can give it a big
bunch of calculations to perform, let it crunch the numbers for several
seconds (or minutes) and then retrieve the results.

  However, generally speaking, a raytracer like POV-Ray cannot do that.
You could delegate some calculations to the GPU, but the amount of
calculations the GPU could do before the results would have to be retrieved
by POV-Ray would be way too small. Transferring data between the CPU and
the GPU has so much overhead that it overwhelms any advantage the GPU might
have over the CPU if the data has to be transferred continuously.

  If you could put the entire scene into the GPU and implement eg. the
ray-object intersection routines completely on GPU, that would be of
great help in the raytracing process (because POV-Ray could make the GPU
calculate a whole bunch of intersections at a time and then retrieve them
all in one single data burst). However, you would have to basically
replicate most of the POV-Ray code code as GPU code, with support for
all possible primitives and optimizations (such as bounding box hierarchies),
and that's just not possible.

-- 
                                                          - Warp

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