Graphics company ATI, long time critic of competitor Nvidia's video card driver optimizations, concedes to using undocumented optimizations of its own.
After criticizing rival Nvidia for using optimized trilinear filtering algorithms in its PC graphics card drivers--calling them "unacceptable tricks" in a recent presentation to hardware reviewers last month--ATI Technologies has acknowledged using similar optimizations itself.
The graphics company's admission was a response to allegations raised by German Web site ComputerBase.de. ComputerBase.de staffers voiced concerns that ATI was possibly using application specific cheats or optimized filtering algorithms after observing that the company's drivers rendered colored mipmaps, such as those used in synthetic image quality tests, with full trilinear filtering enabled, but the filtering method seemed to change under real game conditions in Unreal Tournament 2003.
For the layman, mipmaps are a sequence of textures, each of which is a progressively lower resolution representation of the same image. Mimicking real life, where people perceive less detail the farther they are from a subject, games use detailed mipmaps in areas closest to the player's viewpoint while using less detailed mipmaps in more distant areas.
News source: GameSpot