Anisotropic Filtering and FSAA Performance

We'll take a look at the performance impacts of the various modes of Anisotropic Filtering and FSAA available on the GeForce 6600 GT AGP. For these tests the Firing Squad Far Cry demo was used at a resolution of 1024x768.

At 1024x768 this Far Cry test doesn’t have too large texturing demands, causing large Anisotropic Filtering performance drops, with only 11% of the 1x performance dropped at 16x AF. What we can see is that the increased levels of AF are giving lower performance drops in relation to the previous AF level – this is due to the fact that fewer surfaces will require the maximum level of Anisotropic filtering applied for each level.

With the FSAA levels offered by the 6600 GT we see that 2X FSAA has the smallest performance drop, in absolute terms as well as relative to the preview level. 4x FSAA is reducing the performance by nearly 38% in relation to normal rendering, which is likely due to the bandwidth requirements on this 128-bit bussed board. 8xS has the highest performance penalty, but this is not purely due to the higher bandwidth requirements, but also because 8xS utilises some super-sampling, mixed with multisampling, which requires everything to be rendered multiple times per pixel.

The relative performance differences for the levels of FSAA don’t change that much with 16x AF enabled at the same time, although in this case the 2x FSAA performance hit is a little higher.