scott wrote:
>> How about, say, volumetric fog? ;-)
>>
>> I have yet to see any GPU of any description get that right...
> 
> A couple of papers show how to do realistic physics-based smoke/cloud 
> true volumetric effects (not just static fog):
> 
> http://developer.download.nvidia.com/presentations/2007/gdc/RealTimeFluids.pdf 
> 
> http://www.markmark.net/dissertation/harrisDissertation.pdf
> 
> Also real-time volumetric lighting is no problem, in fact Crysis uses it 
> and I'm sure there's an nVidia demo kicking about somewhere.

All I know is that every time I play HalfLife 2 (hailed for it's 
ground-breaking graphics), I'm struck by how cheese and lame all the fog 
effects look.

Crysis? Isn't that that game that requires a small render farm to play? ;-)

>> For that matter, I've yet to see any GPU do physically correct 
>> reflections [although surely it can't be *that* hard?],
> 
> The reason there is no effort put into doing this is because doing the 
> reflection/environment map method is good enough.

Probably.

>> nor global illumination that isn't pre-computed [and hence won't 
>> change when objects move around].
> 
> http://realtimeradiosity.com/demos/
> 
> Real time ambient is done in the "Cascades" demo from nVidia.  Each 
> voxel on the surface traces out (32 IIRC) rays to work out the GI at 
> that point.  OK so it's not perfect (other geometry doesn't affect it) 
> but it's certainly better than no GI.

Cascades sounds interesting. I'd certainly like to watch it. However, it 
requires a more expensive GPU and a more expensive OS before it will 
even consider running, so that's kind of the end of that.

> What you have to bear in mind with all these things, is that they have 
> to be designed to work when a frame takes 15 ms to render.  If reducing 
> the accuracy by 10% speeds up rendering by 50%, the speed-up option is 
> taken. Always.

Yes. And that is why POV-Ray can do things that a GPU can't. POV-Ray 
isn't *trying* to be real-time. ;-)

I could add things like isosurfaces to the list. (Have you ever seen a 
game where the water *actually ripples* rather than just surface normal 
tricks?) The point is, POV-Ray has vastly more time to spare, so of 
*course* it can do a better job than any GPU can. Hardly surprising, really.

Just don't try to tell me a GPU can do everything POV-Ray can. ;-)

-- 
http://blog.orphi.me.uk/
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