ATi Radeon X800 XT PCIe Page 6

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Image Quality

ATi’s GPUs have since the 9700 Pro supported programmable multi-sampling modes of anti-aliasing. In addition, the X800 does not possess a hardware ROP (render output) limitation, allowing for more than four sub-samples to be used. While the AA modes are programmable, when enabled via the control panel a static, sparse sampling pattern is used, and to which ATi applies a gamma correction that gives the X800’s AA a slight quality advantage with thin lines or along edges with a sharp color contrast. And while the X800 is capable of supporting super-sampling, ATi has chosen to not expose this mode of anti-aliasing for their products. Regardless, using Colourless’ D3D FSAA viewer the sparse sampling pattern of the X800s can be seen below:

4x AA Sampling Pattern

4x AA Sampling Pattern

6x AA Sampling Pattern

6x AA Sampling Pattern

Temporal AA is a feature that takes advantage of the programmable sampling patterns available in ATi hardware since the R300. By changing the sampling pattern used per frame, temporal AA increases the visual quality of the AA mode enabled to an appreciable degree. The caveat with the feature, however, is that frame rate must stay high or the changing sampling patterns will become apparent to the human eye, resulting in a flickering along polygon edges that detracts from the AA quality. Enabling temporal AA, however, also enables V-Sync. The performance of the various anti-aliasing modes were tested using IL2: FB AEP’s “Black Death” track.

Black Death Track

As we can see above, 6x AA obviously incurs a higher performance impact than 4x AA, though IL-2 remains fairly playable even at 1600×1200 and certainly looks amazing. Temporal AA, however, is really only useful forIL-2 when configured with maximum settings at the lower resolutions, since the lower frame rate will result in the shifting patterns becoming noticeable. Again, because V-sync is enabled with temporal AA, its scores are lower than the other 4x AA numbers since the frame rate is unable to go above the refresh rate; otherwise, temporal AA has no impact beyond regular AA modes. Visually, however, for games that can maintain high frame rates, temporal AA significantly increases the anti-aliasing quality and really has to be experienced hands-on to be truly appreciated.

According to ATi, A.I. examines a game’s textures as they’re loaded and, using an adaptive filtering algorithm, evaluates how to best filter them from a performance perspective without causing a noticeable degradation in filtering quality. The setting of low for A.I. enables all title-specific optimizations and the adaptive filtering algorithm, while the high setting also enables the optimizations as it increases the aggressiveness of the filtering algorithm. The filtering differences can be seen in these images, created using the Direct3D AF Tester utility:

Direct3D Anisotropic Filtering (AF) Test Results

Optimizations Off Optimizations On
A.I. Off A.I. High

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