> Yeah, I'm reading about it now. (Hmm, I guess I'm not the only person who 
> still thinks 512 MB RAM is a lot. ;-)

For a games console it's probably enough.  What do you hold in RAM during a 
game?  All the 3D meshes and textures are on the GPU video memory only*. 
Probably only the code, collision meshes, map data?  And the PS3 OS is 
vastly simpler than Windows, so I doubt that uses up much RAM.

* When you write a game under Windows, you must keep all the GPU data 
mirrored in normal RAM, because if the user Alt-Tabs to a different 3D game, 
you need to refill the GPU memory quickly (and not go through some long 
load-from-disk process) when the user comes back to your app.  On a games 
console you don't need to do this, because (at least on the PS3) you have to 
quit one game before you can go into another.

> It's a completely different algorithm to be sure. The mathematics is 
> simple enough - it's figuring out how to make it efficient on real-world 
> hardware that's the hard part. ;-)

There was a nice paper I read in a book a while back (one of the GPU gems 
series I think), where some algorithm was explained for doing correct 
multi-level reflections on the GPU.  It was quite complex, involving 
generating lots of cube-maps with depth and texture information and some 
ray-tracing steps in a pixel shader.  In the end they compared the output 
with a real raytracer, and the results looked identical, but the GPU version 
ran at about 10fps IIRC with something like 4 levels of reflection.  The 
real raytracer (Maya I think) was measured in minutes.

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