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- 25 Aug 2004
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I was over at the steam forums and saw this article and thought I would post it here.
http://www.theinquirer.net/?article=23594
I cant wait
http://www.theinquirer.net/?article=23594
I cant wait
ATI did this by using some Z optimisations, removing unseen pixels before running through the pixel shaders. I guess that this is an allowed method and Halo might be running even fifteen per cent faster.
Son Goku said:But what exactly they will remove, and how this will impact performance....
LordOfLA said:Uhm, hate to be a smart ass but they will remove unseen pixels. You will get a speed increase because the shader engine then doenst waste time processing them.
Kinda obvious from the article really
Depending on the number of unseen pixels that get removed, there is a possibility for some performance increase. Anyone familiar with the differences between a tiler (though the card obviously won't become one) and the traditional gfx architecture will know what I'm getting at here. The Prophet 4500 was able to get some performance increase (being a tiler) but not rendering unseen pixels...
If you aint gonna see it, the card wont process them.
ATI did this by using some Z optimisations, removing unseen pixels before running through the pixel shaders.
Some competitors (both 3Dfx and Nvidea) of PowerVR keep saying that the technique doesn't work or will run into trouble when scenes get more complex.
The last step is obvious, when the tile is completely rendered it can be transferred to the big frame buffer in graphics memory. In this last move dithering can be done (so only 1 time instead of several times !) or you can do anti-aliasing by down filtering this on chip tile using bicubic filters and storing the result in a lower resolution in the big frame buffer. All these actions are part of the pipeline.
How is this different from the traditional architectures?
Traditional architectures, like 3Dfx Voodoo2 - Riva TNT and others, work on a per polygon basis. This means that their pipeline will take a triangle render it, take the following triangle and render it, and take again the following triangle and render it,... this means that they do not know what is still to come. PowerVR uses an overview of the scene to decide what to render, traditional renderers just rush into it and do a lot of unnecessary work. The following figure shows this:
We have all heard that PowerVR doesn't have a Z-Buffer and instead uses a Hidden Surface Algorithm ( performed by the ISP ) . Well it is for that Hidden Surface Algorithm that PowerVR needs to use Infinite Planes. The Hidden Surface Algorithm is based on Ray Tracing Principles...