The Cost of FSAA

While anti-aliasing can prove to be beneficial in the reduction of "jaggies", it doesn't come without a performance hit. For demonstrating Full Scene Anti-Aliasing with the Radeon X1800XT under Linux, this afternoon I fired up Quake 4. The FSAA tests today are focused solely upon Quake 4 in a single environment, therefore the performance delta may change depending upon the configuration. FSAA can be toggled through aticonfig and the options of --fsaa={on|off} and --fsaa-samples={off,0,2,4,6}. FSAA gamma can also be adjusted similarly using aticonfig. With Quake 4, a time-demo benchmark was used from the Purification Center map. The game was running in 1152 x 864 windowed mode on the X1800XT Big Desktop configuration with high quality settings within the game itself. Quake 4 v1.2.1 tests were run with 0, 2, 4, and 6 FSAA samples per pixel. Below are the initial anti-aliasing frame-rate results.

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Quake 4 v1.2.1 (Average FPS)
ATI fglrx X1800XT FSAA Tests
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0: 41.2
2: 40.8
4: 37.5
6: 33.4

For a visual comparison, below are three views comparing FSAA being disabled, and then when it was set to the maximum six samples per pixel. The views on the left are with zero FSAA samples, while the right hand side is with six.