PDA

View Full Version : ATIís CATALYST A.I. Ė Honest Application Specific Optimizations



Yawgm0th
09-21-2004, 06:13 PM
Very interesting. This is something I'll have to look into. I can't see any quality reduction in Doom 3, but there is a fairly simple way to notice the difference.

In Mozilla Firefox 1.0 at 1024x768, I opened these two images in tabs and scrolled down as far as possible so they lined up perfectly:
http://www.tweaktown.com/popImg.php?img=catalystai_doom3aionaa.jpg
http://www.tweaktown.com/popImg.php?img=catalystai_doom3aioffaa.jpg

There is a clear difference in the floor on the lower right as you switch between the two, regardless of how observant you are. With AI on, it clearly gets darker. I don't know if this is necessarily a bad thing, but there's the difference you were looking for.
:smilies13

[RS]boreal
09-27-2004, 12:18 AM
Great job I can see the differences but what is AI LOL.

Yawgm0th
09-27-2004, 02:28 AM
Artificial Intelligence.

sr4470
11-23-2004, 03:55 AM
That difference makes sense because Catalyst A.I. uses a "mathematically equivalent" but different light shader in Doom 3 that improves performance of ATI cards. That light difference reminds me of the difference between DX8 and DX9 lighting i read somewhere (much more colour and brightness dymanics with DX9)...looks almost like a lower precision in the lighting calculations.

Frankly shader replacement is something that Nvidia got in a lot of trouble for with the GeforceFX (32bit colour precision was too slow, so they replaced some shaders or ran at 16bit precision which lowered the image quality. They didnt have 24bit mode like ATI does which was the best compromise between speed and quality). At least Catalyst A.I. can be turned off, though ive found in the regular ATI control panel driver set (i.e. not the CCC) Catalyst A.I. does exist, but permanently on the "low" setting and not a visible option to switch off.