NVIDIA GeForce 7800 GTX

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Image Quality: Anti-Aliasing

Prior to benchmarking the new GeForce 7800 GTX, we spent some time analyzing its in-game image quality versus a GeForce 6800 Ultra and a Radeon X850 XT Platinum Edition. First, we used the "background 4" map in Half-Life 2 to get a feel for how each card's anti-aliasing algorithm's affected the scene...

Image Quality Analysis: Anti-Aliasing
7800 vs. 6800 vs. X850XT

GeForce 7800 GTX
1280x1024 - No AA

GeForce 7800 GTX
1280x1024 - 4X AA

GeForce 7800 GTX
1280x1024 - No AA

200% Zoom

GeForce 7800 GTX
1280x1024 - 4X AA

200% Zoom

GeForce 6800 Ultra
1280x1024 - No AA

GeForce 6800 Ultra
1280x1024 - 4X AA

GeForce 6800 Ultra
1280x1024 - No AA
200% Zoom

GeForce 6800 Ultra
1280x1024 - 4X AA
200% Zoom
_____________________________________________________________

Radeon X850XT PE
1280x1024 - No AA

Radeon X850XT PE
1280x1024 - 4x AA

Radeon X850XT PE
1280x1024 - 6x AA

Radeon X850XT PE
1280x1024 - No AA

200% Zoom

Radeon X850XT PE
1280x1024 - 4x AA

200% Zoom

Radeon X850XT PE
1280x1024 - 6x AA

200% Zoom

If you direct your attention to the water-tower and crane in the background of the image, the impact anti-aliasing has on image quality is readily apparent. In the "No AA" shots it seemed to us that the Radeon X850 XT Platinum Edition had the lowest detail, and had the most prominent "jaggies." Look closely at the ladder on the water tower and you'll notice parts missing in the Radeon shots that are there on both GeForce cards.

With 4X anti-aliasing enabled, the "jaggies" in the scene are cleaned up considerably, but it's extremely difficult to perceive any real differences in the images, even while zoomed, although the cables on the crane seem slightly more defined on the Radeon. We've also included a sample using ATI's 6X AA mode, which was the best overall. (NVIDIA doesn't support this mode.)

Image Quality Analysis: Transparency Anti-Aliasing
Something New For An Old Problem

As we mentioned earlier, the GeForce 7800 GTX supports a new anti-aliasing mode that improves the look of aliased textures that use transparency to simulate geometry. This trick is commonly used on grass or trees to produce lush environments without immense amounts of geometry. A texture that looks like grass or a branch, for example, is mapped onto a simple polygon, and because you can see through the transparent portions of the texture, it seems as though each blade of grass or branch is distinct. The problem with this technique is that multi-sampling anti-aliasing does not eliminate the "jaggies" because they are not along the edge of a polygon. But with the GeForce 7800 GTX, NVIDIA has enabled a new feature to combat this problem.


GeForce 7800 GTX
1280x1024 - 4X AA

with Multi-Sampling
Transparency AA

GeForce 7800 GTX
1280x1024 - 4X AA

with Super-Sampling
Transparency AA

Radeon X850XT PE
1280x1024 - 6x AA

GeForce 7800 GTX
1280x1024 - 4X AA

with Multi-Sampling
Transparency AA

200% Zoom

GeForce 7800 GTX
1280x1024 - 4X AA

with Super-Sampling
Transparency AA

200% Zoom

Radeon X850XT PE
1280x1024 - 6x AA

200% Zoom

When looking at the screen shots above, focus on the detail in the branches and the blades of grass. When you do, you'll notice that the GeForce 7800 GTX, especially when super-sampling transparency anti-aliasing is used, produced a much cleaner, more realistic image. Portions of the tree that are completely missing on the Radeon X850 XT Platinum Edition are clearly visible with the GeForce 7800 GTX.

NVIDIA was intentionally tight-lipped and didn't explain how transparency anti-aliasing works in-depth, but the results speak for themselves. With transparency anti-aliasing enabled, on top of NVIDIA's standard anti-aliasing mode, the GeForce 7800 GTX produced the cleanest images of the bunch.

 

Great visuals always come at the expense of performance, though, so we ran a couple of tests with Half-Life 2 with both multi-sampling and super-sampling transparency anti-aliasing enabled in conjunction with NVIDIA's standard anti-aliasing algorithm. As you can see, enabling either transparency anti-aliasing mode had a negligible impact on performance in Half-Life 2. In fact, with multi-sampling transparency AA enabled, we got slightly higher frame rates. We asked NVIDIA if there was a problem with this mode in the driver revision we used for testing and were told there was no problem, and that the impact of performance was trivial.

Tags:  Nvidia, GeForce, GTX, force, GT, 7800, 780, id

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