An examination of texture filtering under Direct3D was done using Unreal Tournament 2004, which supports application controlled texture filtering via the LevelOfAnisotropy setting in the UT2004.ini file. Anisotropic filtering can also be configured within the game by entering "preferences" in the console and selecting the rendering option in the advanced options applet.
Ironically, it was Unreal Tournament 2003 that brought about a number of investigations (here and here) concerning NVIDIA's past texture filtering optimizations, which were specifically targeted at the GeForce FX architecture.
UT2004 - Inferno
NVIDIA's response to driver optimizations was unveiled last October at Editor's Day 2003. A presentation by Nick Triantos, Director of Software Engineering, explained the optimization policy that NVIDIA began implementing at that time.
We have strict guidelines in place to ensure that questionable optimizations do not get introduced in future driver builds. All future optimizations must pass the following checkpoints before they can be checked in to the driver:
An optimization must produce the correct image.
An optimization must accelerate more than just a benchmark.
An optimization must not contain a precomputed state.
In our view, if an optimization produces the correct picture, it is beneficial to the user and is legitimate. If a change in the driver does not produce the correct picture, or functions only in the benchmark, it is either a bug and must be fixed, or a cheat.
While application specific optimizations are beneficial, they must be done without compromising image quality.
UT2004 - Face3
One reason why Unreal Tournament 2004 is graphically rich is due to the generous amount of texture blending operations that take place in the rendering engine. Complex texture blending operations are often referred to as texture stages, which provide special graphics effects like bump mapping, dual texturing, light mapping and environment mapping.
Graphics chipsets like the GeForce 6 Series provide hardware acceleration for texture blending operations. However, these operations, combined with trilinear and anisotropic texture filtering algorithms, can quickly become computationally intensive. Direct3D supports the blending of up to eight textures, which are numbered 0 through 7.