These textures won’t benefit from filtering.
Other textures in the game store important data that the game uses to render scenes, but don’t show up on screen. Instead, it sets filtering on a per-texture basis, requesting filtering only on those textures that require it. Unlike most games, they claimed, DOOM 3 doesn’t turn on anisotropic texture filtering globally.
The problem with image quality, they said, is due to a known bug in the Catalyst 4.8 and early 4.9 beta drivers. We contacted ATI and asked for an explanation, unsure what to expect.ĪTI’s answer, it turns out, was intriguing. There might also be something fishy going on, because performance drops after toggling the filtering mode in the game console. Once you’ve done that, the transition line on the floor magically vanishes:Īpparently, something is wrong with ATI’s drivers, because the Radeon X800 Pro isn’t producing the correct image in DOOM 3 at the game’s defaults. Then you can flip back into trilinear mode with this command: That will put the renderer into bilinear filtering (and shouldn’t affect anisotropic filtering). The command to turn off trilinear and just run bilinear filtering in DOOM 3 is similar to what you’d use in old Quake engine games, but slightly different: One way around this problem is to use DOOM 3’s console commands to flip out of trilinear filtering and then back into it. DOOM 3’s own gamma and brightness settings don’t affect screenshot output, and the game’s output is a little too dark by default for our purposes.) (By the way, all the images from DOOM 3 in this article have been brightened up a bit by using a gamma 1.4 on them in Paint Shop Pro. We used the Catalyst 4.9 beta drivers that ATI released specifically for DOOM 3 to take this screenshot, but the exact same problem is visible with ATI’s latest official drivers, Catalyst 4.8. Having those things track on the floor out in front of me as I moved was annoying. Once you’ve noticed it, it’s rather distracting, like the transition lines were with bilinear-only filtering on Voodoo cards back in the Quake 2 days. The screenshot shows the problem, but it’s more obvious in motion.
This problem is visible throughout the game whenever a similar texture is used on the floor. However, as you can see, there’s a mip map transition line running across the middle of the grate on the floor in our example screenshot. This is in DOOM 3’s High Quality mode, where 8X anisotropic filtering and trilinear filtering are both supposed to be active. (Click for full-screen lossless PNG version) Radeon X800 Pro with Catalyst 4.9 beta – Game defaults There is a clearly visible transition between mip map levels, as if trilinear filtering were not happening as it should. Textures with high-contrast patterns on them, like the metal grates in the game’s Mars base, tend to show the problem most vividly. The problem with ATI’s drivers in DOOM 3 has to do with texture filtering, and it is more visible on some textures than others. So we fired up our test rigs, busted out our sleuthing skills, and set out to see what exactly was happening with ATI’s drivers in DOOM 3. We’ve dug into such juicy stories in the past, and the results have sometimes been rather enlightening. Naturally, we were interested in the possibility of uncovering such a scandalous thing. What’s more, this problem seemed to be specific to DOOM 3, raising the possibility that ATI was guilty of engaging in an application-specific optimization-a practice the firm has forsworn. R ECENTLY, WE RECEIVED a tip, some information claiming ATI’s drivers exhibited some odd behavior in DOOM 3 and that the company might be compromising image quality for performance.