Allen wrote:
> Would it be possible to use the GPU as well as the CPU to render?  This
> could speed up render times so much and would allow a somewhat crappy
> machine to generate some pretty spiffy results.
> 

I think this is one of those recurring questions, and generally the 
answers I've seen come down to "no of course not."  I'm no expert - I 
speak with less knowledge on this than many who've answered this 
question before, but I'm not entirely confident that "no of course not" 
will always be the answer.

Anyway....

While the 'G' in GPU's are moving more towards "General" as opposed to 
"Graphics," it'd be hard, for one thing, since their floating point 
calculations are generally single precision and in POV-Ray everything's 
double.   I'll add that even with double precision, people trying to 
make things like spacecraft near planets to-scale run into practical 
limitations:  POV-Ray won't necessarily render everything - parts of an 
object may vanish.

Another matter is how large of chunks of functionality should be loaded 
into the card at once (afterall, you'd be using the GPU as a CPU or some 
sort of co-processor, not for its built-in shading).  Another issue 
would be platform independence when you're talking about graphics 
cards.... That could be interesting.

On a 'POV4' note, I wonder how hard it'd be to make it simple* to choose 
what math library to use at compile time?  I.e. not even having doubles 
as the only option.... DO compile using single precision, or DO use one 
of those variable-precision (slow) libraries, or if somebody were to 
write something that'd send floating point calculations (disregarding 
whether it'd be effective or not) to the graphics card**, they could do 
so?  Somebody using 'insane' scale differences might be willing to deal 
with the slowness of an added-precision library, and somebody wanting to 
experiment with GPGPU could do so too.

I think all use of alternate math libraries would be non-standard 
compilations of POV-Ray and thus resultant images wouldn't necessarily 
be the same as one rendered with official POV-Ray.  But who cares? 
They'd know it's non-standard.  Am I right in saying that being able to 
switch to a non-standard or platform-dependant library easily wouldn't 
break portability?

Charles

*It may already be simple for all I know.  I haven't looked into it. I'm 
just talking.

**Maybe that person would choose to promote returned single precision 
floats to doubles at reduced quality.

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