KingFish
31 Aug 2004, 2:41am
Recently some information claiming ATI's drivers exhibited some odd behavior in DOOM 3 and that the company might be compromising image quality for performance. 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.
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. Textures with high-contrast patterns on them, like the metal grates in the game's Mars base, tend to show the problem most vividly. There is a clearly visible transition between mip map levels, as if trilinear filtering were not happening as it should. Here's an example. This is in DOOM 3's High Quality mode, where 8X anisotropic filtering and trilinear filtering are both supposed to be active. 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 problem is visible throughout the game whenever a similar texture is used on the floor. The screenshot shows the problem, but it's more obvious in motion. 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. Having those things track on the floor out in front of me as I moved was annoying.
Source: Tech Report (http://www.techreport.com/etc/2004q3/ati-doom3/index.x?pg=1)
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. Textures with high-contrast patterns on them, like the metal grates in the game's Mars base, tend to show the problem most vividly. There is a clearly visible transition between mip map levels, as if trilinear filtering were not happening as it should. Here's an example. This is in DOOM 3's High Quality mode, where 8X anisotropic filtering and trilinear filtering are both supposed to be active. 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 problem is visible throughout the game whenever a similar texture is used on the floor. The screenshot shows the problem, but it's more obvious in motion. 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. Having those things track on the floor out in front of me as I moved was annoying.
Source: Tech Report (http://www.techreport.com/etc/2004q3/ati-doom3/index.x?pg=1)