MSAA 4x/8x vs. CSAA 16x/16xQ
Elder Scrolls: Oblivion
The main and loudly touted feature of CSAA is that it needs less resources than the classic multisampling. Nvidia claims the performance in 16x CSAA mode is going to be just a little lower than at 4x MSAA. We’ll talk about the speed factor below. Right now let’s discuss the quality factor.
16x CSAA ensures a higher-precision antialiasing in comparison with 4x MSAA, especially on small scene details, because it uses 4 times the number of coverage samples. It keeps the same color information as 4x MSAA, so the smoothed-out edges of polygons may look not as ideal as they would be with 16x MSAA.
Such a high level of multisampling would be too heavy even for the GeForce 8800 GTX, but we can compare 16x CSAA with 8x MSAA. The difference is smaller here and can hardly be revealed even with TheCompressonator, but 8x MSAA calculates the final pixel color with more accuracy than 16x CSAA does and, unlike 4x MSAA, doesn’t suffer much from the errors at determining if a pixel belongs to the smoothed-out polygon. 8x MSAA looks obviously better than 16x CSAA in terms of image quality, but we shouldn’t forget about speed.
It’s even harder to see the difference between 16x CSAA and 16xQ CSAA which stores more information about the color and depth (8 samples instead of 4), but 16xQ CSAA is surely the highest-quality antialiasing mode available today on a single graphics card.
CSAA 16x/16xQ vs. SLI AA 16x
Elder Scrolls: Oblivion
It’s similar to the above-described situation with 8x CSAA, 8xS FSAA and 8x SLI AA, but with more conspicuous symptoms. The 16x SLI AA mode performs antialiasing on transparent surfaces like the foliage or wire fence, but also makes the scene somewhat blurry. Some small details may be lost, like the relief on the masonry in Oblivion . Besides that, 16x SLI AA requires two graphics cards whereas the 16xQ CSAA mode provides higher sharpness and works on a single GeForce 8800, so it is indeed the highest-quality antialiasing method available on single graphics cards.
Beside comparing the quality of the new full-screen antialiasing modes implemented in the GeForce 8800, we also decided to check out the quality of anisotropic filtering provided by ATI’s and Nvidia’s flagship products. GeForce 7 series cards are expelled from this test as not compliant with the high image quality standards. For the Radeon X1950 XTX we enabled the High Quality AF mode. Here are the results:
The Nvidia GeForce 8800 uses the new anisotropic filtering always irrespective of enabled/disabled optimizations and the filtering quality mode, High Quality or Quality. In the latter case the transition between the mip-levels degenerate and the filtering quality isn’t high, yet it doesn’t depend much on the angle of inclination of the plane of the filtered texture.
In the High Quality mode the quality of anisotropic filtering provided by the GeForce 8800 GTX is nearly ideal and free from any defects. It is even higher than that of the Radeon X1950 XTX, the recognized ex-leader in this area. The diagram with the colored mip-levels shows the characteristic surges that are indicative of the not-exactly-true method of anisotropic filtering employed by the ATI card – there are certain “inconvenient” angles with this method. The new algorithm from Nvidia is free from this defect. Note also that ATI’s algorithm is somewhat more aggressive as is visible on the textures closest to the user which are sharper than on the GeForce 8800. This may result in the effect of “flickering” textures in games.