X-bit labs

ATI RADEON X800: R420 Totally Exposed (page 20)

Category: Video

by Tim Tscheblockov , Alexey Stepin , Anton Shilov

[ 05/04/2004 | 06:42 AM ]

Finally, let’s take some random angle for the polygon edges. In the fourth fragment it will be around 60^o. The screemshots follows in the same order: ATI RADEON X800 XT Platinum Edition, RADEON 9800 XT, NVIDIA GeForce 6800 Ultra and NVIDIA GeForce FX 5950 Ultra.

FSAA 2x

FSAA 4x

FSAA 6x/8x

In 2x mode on this fragment the graphics cards cannot provide acceptable anti-aliasing quality. The quality is especially poor on ATI based graphics cards: the polygon edge angle is close to the diagonal where RADEON 9800 XT and RADEON X800 XT locate their subpixels.

When we enable 4x mode, the situation changes to the contrary: ATI RADEON 9800 XT/X800 XT and NVIDIA GeForce FX 5950 Ultra provide good image quality, while for NVIDIA GeForce 6800 Ultra in 4x mode this angle becomes “inconvenient”.

In 6x/8x modes all graphics cards cope with polygon anti-aliasing perfectly well.

So, if we sum up everything we have just discussed, regarding the polygon edges anti-aliasing by the new NVIDIA and ATI processors, we will be able to conclude the following. In 2x mode it is almost identical. In 4x mode the laurels go to ATI, which manages to ensure a more realistic picture provided by the new RADEON X800 due to gamma-correction during multi-sampling. In 6x/8x modes NVIDIA has an advantage due to bigger number of samples, while ATI again succeeds due to gamma-correction algorithms.

It is interesting that in 2x and 4x modes all graphics cards use “pure” multi-sampling that is why the performance loss when these modes are enabled should be about the same by all graphics cards. But then the differences emerge. ATI in 6x mode still uses multi-sampling, while NVIDIA in 8x mode uses a combination of multi-sampling and super-sampling. It is evident that this hybrid 8x mode by NVIDIA GeForce FX 5950 Ultra and GeForce 6800 Ultra will slow down the graphics card performance compared with that of ATI solution in 6x mode, although it will definitely provide better image quality due to improved texturing algorithm and alpha-textures anti-aliasing as a result of super-sampling.

However, why should we guess what the performance will look like? Let’s test our cards in real gaming applications to see how big the performance drop is going to be when we enable full-screen anti-aliasing on the new solutions from NVIDIA and ATI.