Texture filtering quality and performance
Fortunately, Nvidia has chosen to take advantage of the G80's additional texture filtering capacity to deliver better default image quality to PC graphics. This development will no doubt be welcome news to those have been subjected to the texture crawling, moire, and sparkle produced by the default anisotropic filtering settings of the GeForce 7 series.

In order to show you how this works, I'm going to have you look at a trio of psychedelic drawings.

Default quality
GeForce 7900 GTX	Radeon X1950 XTX	GeForce 8800 GTX

For the uninitiated, these are resized screenshots from 3DMark's texture filtering test app, and what you're doing here is essentially staring down a 3D rendered tube. The red, green, and blue patterns you see are mip maps, and they're colored in order to make them easier to see. On all three GPUs, 16X anisotropic filtering is enabled.

You'll want to pay attention to two things in these screenshots. The first is the series of transitions from red to blue, blue to green, and green to red. The smoother the transition between the different mip levels, the better the GPU is handling a key aspect of its filtering job: trilinear filtering. The Radeon appears to be doing a superior job of trilinear filtering in the picture above, but I wouldn't get too excited about that. ATI uses an adaptive trilinear algorithm that does more or less aggressive blending depending on the situation. In our case with colored mip levels, the adaptive algorithm goes all out, filtering more smoothly than it might in a less contrived case.

Still and all, the G71's trilinear looks kinda shabby.

The other thing to notice is the shape of the pattern created by the colored mip maps. Both the G71 and R580+ go for the "wild orchid" look. This is because they both practice a performance optimization in which the amount of anisotropic filtering applied to a surface depends on its angle of inclination from the camera. The tips of the flowers are the angles at which the weakest filtering is applied. At some point, somebody at ATI thought this was a good idea, and at another point, Nvidia agreed. Happily, that era has passed with the introduction of the G80, whose default aniso algorithm produces a nice, tight circle that's almost perfectly round.

To illustrate how this filtering mumbo jumbo works out in a game, I've taken some screenshots from Half-Life 2, staring up at a building from the street. The building's flat surface looks nice and sharp on all three cards thanks to 16X aniso, but when you turn at an angle from the building on the G71 and R580, things turn into a blurry mess. Not so on the G80.

Default quality
GeForce 7900 GTX
Radeon X1950 XTX
GeForce 8800 GTX

To be fair to ATI, the R580+ also has a pretty decent aniso filtering algorithm in its "high quality" mode. The quality level drops off somewhat at 45° angles from the camera, but not terribly so. The G71, meanwhile, keeps churning out the eight-pointed flower no matter what setting we use.

All three GPUs, including the G80, produce nicer mip map transitions in their high quality modes.

High quality
GeForce 7900 GTX	Radeon X1950 XTX	GeForce 8800 GTX

High quality
GeForce 7900 GTX
Radeon X1950 XTX
GeForce 8800 GTX

So the Radeon X1950 XT produces decent aniso filtering in its high quality mode, but the G80 does so all of the time. And the G71 is impervious to our attempts to help it succeed.

Now that we've seen how it looks, we can put these performance numbers in context. I've tested with both default and high-quality settings, so the performance difference between the two is apparent. Unfortunately, D3D RightMark won't test FP16 or FP32 texture filtering, so we'll have to settle for just the standard 8-bit integer texture format until we get to our gaming tests.

The G80 cranks out twice the fill rate of the R580+ at 16X aniso, despite having to work harder to produce higher quality images. Very impressive.