Before estimating the quality of anisotropic filtering, let’s have a look at the picture produced by NVIDIA GeForce FX and ATI RADEON 9700 PRO with these settings. We will take a fragment of the scene as an example:

Visually, the quality of the image constructed by NVIDIA GeForce FX in “Application” and “Balanced” modes is similar to ATI RADEON 9700 PRO in the “Quality” mode.

When in the “Aggressive” mode, GeForce FX shows perceptible texture compression artifacts, but they are nothing compared to what ATI RADEON 9700 PRO shows in the “Speed” mode: besides forced compression, the graphics chip greatly reduces the level of textures detail. All this results in a wild-looking “slush”.

So, now that we have already collected some general impressions, let’s go over to estimating the anisotropic filtering quality. Just like in our ATI RADEON 9700 PRO Review, we took screenshots at different surface angles. The fragments of the screenshots are placed in two rows: the upper row shows anisotropic filtering of the maximum level (8x for GeForce FX and 16x for ATI RADEON 9700 PRO) together with tri-linear filtering. The lower row shows bi-linear filtering with highlighted MIP-levels. For comparison, we also show screenshots of NVIDIA GeForce4 Ti4800 in the “Balanced” mode with 8x anisotropic filtering.

ATI RADEON 9700 PRO surpasses GeForce FX in quality on horizontal surfaces: even in the “Speed” mode RADEON 9700 PRO produces no worse picture than GeForce FX. In the “Quality” mode, ATI RADEON 9700 PRO loses in sharpness of distant textures: the higher maximum level of anisotropy (16x against 8x in GeForce FX and GeForce4) tells here.

It’s interesting that even when tri-linear filtering is disabled in the “Quality” mode, the picture with highlighted MIP-levels on RADEON 9700 PRO looks like it’s still on. This effect is due to the ATI’s “house” anisotropic filtering method in the “Quality” mode: the resulting color is calculated from the colors of two texels taken from two neighboring MIP-levels with weights varied according to the remoteness of the pixel.

It’s rather hard to tell one mode of GeForce FX from another: “Application”, “Aggressive” and “Balanced” look much alike. Only the highlighting of MIP-levels makes clear the change in textures level of detail.

This angle (22.5^o) is “inconvenient” for the anisotropic filtering algorithm from ATI. RADEON 9700 PRO exposes to shame its fuzzy textures. NVIDIA GeForce FX, and also GeForce4, keep the same quality of texture filtering.

At the angle of 45^o, ATI RADEON 9700 PRO returns to its normal quality and beats the competitors in image quality.

GeForce FX still provides visually the same texture filtering quality in all its modes. Only a closer examination shows that the MIP-levels highlight stripes in the “Aggressive” mode are wider than at the 22.5^o angle of inclination. Of course, this is not the “adaptive filtering” from ATI, but just a peculiarity of the level of detail calculation.

So, we see that GeForce FX doesn’t bring any positive innovations over GeForce4 as far as anisotropic filtering quality is concerned. On the contrary, by introducing the mixture of tri-linear and bi-linear filtering instead of true tri-linear filtering they tend to worsen the image quality quite tangibly.

And this worsening does show itself, although it is not that noticeable in static screenshots. When the game is running, that is, the scene is dynamic, this worsening reveals itself on those parts of the picture that do not undergo tri-linear filtering. The worsening looks like “ripples” and clear transitions between MIP-levels on distant objects. Of course, you will hardly notice it in the “Balanced” mode, but is often evident in the “Aggressive” mode.

Anyway, this is not the anisotropic filtering from ATI that works perfect at “convenient” angles, and more than acceptable at “inconvenient” angles.