Company: ATI Technologies
Authour: Alex 'Morgoth Bauglir' Voicu
Editor: Charles 'Lupine' Oliver
Date: April 10th, 2008
Anisotropic filtering is somewhat less glamorous then AA, and has arguably never been the focus of serious marketing pushes, unlike the aforementioned. If AA deals with aliasing in polygon's edges, AF tries to deal with aliasing occurring within polygons, inside textures-it's sometimes referred to as texture-antialiasing. Once more, we'll direct those more technically inclined to a Wikipedia article that has a more in-depth and exhaustive explanation of the process itself. For this article though, it should suffice to say that AF improves the quality of textures significantly, making them appear more crisp and maintaining detail at longer distances from the user's viewpoint.
Just like AA, AF is somewhat costly in terms of performance, and has become feasible only with recent, more powerful GPUs. All current GPUs support a 16:1 (16 to 1) degree of anisotropy (with 2:1, 4:1 and 8:1 as intermediary steps), and all GPUs after the R6XX and the G8X employ a high quality AF algorithm that has reduced angle dependency as standard. The G8X is somewhat more robust on this front, with its algorithm being less angle-dependent than the R6XX's one, but the differences should be almost impossible to spot outside of test scenarios.
Since we now know what the 3870X2 should be able to do, let's see it doing it. For testing AF we'll be using Demirug's D3DAFTester application:
As we said above, some angle dependency remains apparent with the 3870X2's AF, but in most scenarios this shouldn't be noticeable at all.
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