FSAA

FSAA Performance

For the purposes of testing FSAA performance we'll once again use Serious Sam: Second Encounter's Citadel demo. The 'Extreme' Addon was used but with Anisotropic filtering disabled.





 640x480 800x600 1024x768 1280x1024 1600x1200
No AA 110.5 109.2 106.8 99.7 86.2
2X 113.9 110.4 106.4 94.4 72.8
4X 109.8 107.6 99.1 77.9 53.3
6X 109.5 104.9 92.9 64.7 40.6
Diff from No AA 640x480 800x600 1024x768 1280x1024 1600x1200
2X 3% 1% 0% -5% -16%
4X -1% -1% -7% -22% -38%
6X -1% -4% -13% -35% -53%

Because there isn't much in the way of a fillrate limitation for Radeon 9700 PRO under these settings without FSAA, we can see that in many resolutions we are getting AA 'for free'. With 2X FSAA enabled the worst performance drop we see is only 16% at 1600x1200, and this is remaining wee above the 60FPS mark. 4XFSAA shows a bigger drop off over 1024x768, going up to a 38% drop - remarkably at 1024x768 its still above 100FPS and at 1280x1024 only just below; long gone are the days when enabling 4XFSAA meant dropping down to a quarter of the performance! Again, with 6XFSAA we still see very healthy performance with just over 90FPS at 1024x768 and still above 60FPS at 64.7FPS.

With FSAA enabled we can really begin to see that the compression schemes and other overdraw removal elements are operating quite effectively. Under normal circumstance 6XFSAA should require 6 times the bandwidth of normal rendering, and yet here it is only loosing half the performance at1600x1200.

FSAA Quality

Below are some 800x600 screenshots taken from Serious Sam: Second Encounter with the various modes of AA enabled.
No FSAA                              2X FSAA
4X FSAA                               6X FSAA

Here's a selection of some screenshots with the various mode of AA enabled.


No FSAA                              2X FSAA
4X FSAA                               6X FSAA


We can see from the 2X shot that there is distinct AA on both the near horizontal and vertical edges, giving a good indication that some kind of rotated grid is enabled. The 4X shot also appears to show 3 intermediate colour gradients on both types of edge at fairly regular intervals.