New and Improved Texture Filtering
I mentioned in the discussion on the new G80 architecture that the texture filtering units are much improved and offer us better IQ options than ever before. While we haven’t looked at it in depth on PC Perspective recently, there has been a growing concern over the filtering options that both ATI and NVIDIA were setting in their drivers, and the quality they produced. If you have ever been playing a game like Half Life 2 or Guild Wars (probably one of the worst) and noticed “shimmering” along the ground, where textures seem to “sparkle” before they come into focus, then you have seen filtering quality issues.
ATI X1950 XTX – 16x AF – Default Settings – Click to Enlarge
This first diagram shows us what 16x AF at default settings on the ATI X1950 XTX produces in terms of image quality. In short, anywhere you see the colors banding out wards towards the edge of the screen, filtering will be less in that area. At 45 and 135 degree angles (and their inverses) in the above filtering algorithm, filtering is not done as precisely because of the larger amount of processing required at these angles. This is what produces the shimmering and sparkles you see.
ATI X1950 XTX – 16x AF – High Quality AF Settings – Click to Enlarge
ATI started offering a new “high quality AF” mode in their Catalyst driver with the X1900 release, and this greatly enhanced the AF quality levels we saw. It also reduced the shimmering effect I had come to despise.
NV 7900 GTX – 16x AF – Default Settings – Click to Enlarge
On the 7900 GTX, NVIDIA’s default settings look much like the ATI default settings did with the same angle issues seen on the ATI cards.
NV 7900 GTX – 16x AF – High Quality AF Settings – Click to Enlarge
However, even when setting the filtering level to “high quality” NVIDIA’s driver does not allow for much improvement in the filtering quality on the 7900.
NV 8800 GTX – 16x AF – Default Settings – Click to Enlarge
Image quality fanatics rejoice; this is the default setting on the new GeForce 8800 GTX. At 16x AF, the 8800 GTX shows much better filtering quality than even the high quality setting on the ATI X1950 XTX card.
NV 8800 GTX – 16x AF – High Performance AF Settings – Click to Enlarge
Even when set at “high performance” (which we’ve never told anyone to do) the 8800 GTX is impressive.
NV 8800 GTX – 16x AF – High Quality AF Settings – Click to Enlarge
Finally, when setting the 8800 GTX to “high quality” mode in the driver, we see an improvement from the default settings; when you see how much power this card has you might find yourself pretty likely to turn features like this on!