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Christopher James Huff wrote:
> In article <416d6075$1@news.povray.org>, "scott" <sco### [at] spam com>
> wrote:
>
>> Well, if you write a ray-object intersection algorithm that runs on
>> the GPU, that would certainly help a lot. Of course POV-ray would
>> need to be modified (and this will not likely happen, but it could
>> be a patch, or another raytracer entirely). GPUs are *very* fast at
>> doing the same code in parallel. So POV could give the GPU a batch
>> of rays to calculate intersections with, the GPU can go away and do
>> this and return the result when it's done. During this time the CPU
>> can also be doing the same (and working out the pixels from the last
>> GPU result). It would certainly speed things up, look at that link
>> where they guy was getting 30fps from his simple raytracer and then
>> was getting 1200fps when it was running with the GPU helping.
>
> It's still not very useful to POV-Ray. It'd spend too much time
> copying data to and from the card, and pulling data off the card is
> generally not a fast operation...they're optimized for displaying
> triangles and crunching numbers local to the card. What these demos
> are do is basically hard code a simple, small raytracer and scene
> designed around the abilities of the card into the pixel shader. It's
> fast because it all fits on the card and it doesn't do anything that
> needs to move stuff between the card and the main system. In
> addition, precision limitations will be a huge problem...POV uses
> double precision for most calculations, and it needs them. From what
> I've seen, GPUs use half precision...good enough for a demo, but not
> enough for general raytracing.
>
> It's a neat trick, but it's just not general enough to handle what
> POV-Ray needs to do. You might be able to make use of it with a more
> limited raytracer (maybe a scientific visualization app, for example),
> but it's of no help to POV-Ray.
Oh yes, I realise this. Just worth keeping an eye on in the future, I'm
sure the GPUs are going to get more and more complex.
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