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21 February, 2008

I missed that...

...the first time I've read about Capcom's MT engine, so it's not exactly new, but as I was reading again MT documents around the web for my previous article, I've found the following nice trick (here):
MSAA trickery. Another thing the Capcom presentation talks about is their use of MSAA trickery, for increased speed. On the consoles, where you have lower-level access to frame buffer formats, etc. you can do wacky stuff like pretending a 1280×720 (720p) no-AA screen is a 640×360 (ordered grid) 4xMSAA screen. This works, because these would have the same pixel dimensions. By drawing e.g. particles to the 640×360 4xMSAA screen instead of the 720p screen you would reduce your fragment shader computation to 1/4 (as the fragment shader is only executed once per pixel for multisampling), while still rendering to the same pixels as you would have if drawing into the 720p buffer. This is a way of trading fidelity for speed (or vice versa) and it is a very nifty trick.

1 comment:

Codermind said...

That trick is also possible on PC, but since right now it's only accessible to driver developers, it tends not to be used for fear of reviewers backlash (except maybe by some second tier IHV we shouldn't mention). On PC it's all about the best quality ;). Those console guys have it easy.