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Texture filtering quality
You're probably looking at the table below and wondering what sort of drugs will produce that effect. It's not my place to offer pharmaceutical advice, and I don't want to dwell too much on this subject, but the images below are test patterns for texture filtering quality. My main purpose in including them is to demonstrate that not much has changed on this front since the debut of the DirectX 10 generation of GPUs. These are the same patterns we saw in our Radeon HD 2900 XT review, and they're big, honkin' improvements over what the DirectX 9-class GPUs did.

Anisotropic texture filtering and trilinear blending
Radeon HD 3870 Radeon HD 4870
GeForce GTX 280 GeForce GTX 280 HQ

The images above come from the snappily-named D3D AF tester, and what you're basically doing is looking down a 3D rendered tube with a checkerboard pattern applied. The colored bands indicated different mip-map levels, and you can see that the GPUs vary the level of detail they're using depending on the angle of the surface

The GeForce GTX 280's pattern, for what it's worth, is identical to that produced by a G80 or G92 GPU. Nvidia's test pattern is closer to round and thus a little more perfect, but we've found the practical difference between the two algorithms to be imperceptible.

On a more interesting note, the impact of Nvidia's trilinear blending optimizations is apparent. You can see how much smoother the color transitions between mip maps are with its "high quality" option enabled in the driver control panel, and you've seen how that option affects performance on the prior page of this review. Then again, although the Radeon's test pattern looks purty, AMD has a similar adaptive trilinear algorithm of its own that dynamically applies less blending as it sees fit.

The bottom line, I think, on image quality is that current DX10-class GPUs from Nvidia and AMD produce output that is very similar. Having logged quite a few hours playing games with both brands of GPUs, I'm satisfied that either one will serve you well. We may revisit the image quality issue again before long, though. I'd like to look more closely at the impact of those trilinear optimizations in motion rather than in screenshots or test patterns. We'll see.

Antialiasing
The RV770's beefed up texture filtering looks pretty good, but how do those new render back-ends help antialiasing performance? Well, here we have the beginnings of an answer. The results below show how increasing sample levels impact frame rates. We tested in Half-Life 2 Episode Two at 1920x1200 resolution with the rest of the game's image quality options at their highest possible settings.

To get a sense of the impact of the new render back-ends, compare the results for the Radeon HD 3870 X2 and the Radeon HD 4870. The two start out at about the same spot without antialiasing (the 1X level), with the 3870 X2 slightly ahead. However, as soon as we enable 2X AA, the 3870 X2's performance drops off quickly, while the 4870's frame rates step down more gracefully. The 4870 produces higher frames rates with 8X multisampling than the 3870 X2 does with just 2X AA.

I've shown performance results for Nvidia's coverage sampled AA (CSAA) modes in the graph above, but presenting the results from the multitude of custom-filter AA (CFAA) modes AMD offers is more difficult, so I've put them into tables. First up is the Radeon HD 3870 X2, followed by the Radeon HD 4870.

Radeon HD 3870 X2 - Half-Life 2 Episode Two - AA scaling
Base
MSAA
mode
Sample
count
FPS Filter
type
Sample
count
FPS Filter
type
Sample
count
FPS Filter
type
Sample
count
FPS
1X 1 98.0 - - - - - - - - -
2X 2 66.2 Narrow
tent
4 65.5 Wide
tent
6 62.7 - - -
4X 4 65.0 Narrow
tent
6 47.5 Wide
tent
8 46.2 Edge
detect
12 37.7
8X 8 59.1 Narrow
tent
12 26.9 Wide
tent
16 25.5 Edge
detect
24 28.1

Radeon HD 4870 - Half-Life 2 Episode Two - AA scaling
Base
MSAA
mode
Sample
count
FPS Filter
type
Sample
count
FPS Filter
type
Sample
count
FPS Filter
type
Sample
count
FPS
1X 1 96.3 - - - - - - - - -
2X 2 84.4 Narrow
tent
4 69.3 Wide
tent
6 66.3 - - -
4X 4 79.8 Narrow
tent
6 52.5 Wide
tent
8 51.3 Edge
detect
12 39.5
8X 8 73.1 Narrow
tent
12 31.6 Wide
tent
16 29.2 Edge
detect
24 28.8

The thing that strikes me about these results is how similarly these two solutions scale when we get into the CFAA modes. The 4870 is quite a bit faster in the base MSAA modes with just a box filter, where the render back-ends take care of the MSAA resolve step. Once we get into shader-based resolve on both GPUs, though, the 4870 is only slightly quicker than the 3870 X2 in each CFAA mode. That means, practically speaking, that RV770-based cards will pay a relatively higher penalty for going from standard multisampled AA to the CFAA modes than R6xx-based ones do. You're simply better off running a Radeon HD 4870 in 8X MSAA than you are using any custom filter. That's not a problem, of course, just an artifact of the big performance improvements delivered by the RV770's new render back-ends. Many folks will probably prefer to use 8X MSAA given the option, anyhow, since it doesn't impose the subtle blurring effect that AMD's custom tent filters do.

Incidentally, the RV770's performance also scales much more gracefully to 8X MSAA than any GeForce does. The Radeon HD 4870 outperforms even the mighty GeForce GTX 280 with 8X multisampling, and the 4850 practically trounces the 9800 GTX. Believe it or not, I'm already getting viral marketing emails from amdguyintoronto@hotmail.com asking me to test more games with 8X AA. Jeez, these guys are connected.