X-bit labs

ATI RADEON X800: R420 Totally Exposed (page 12)

Category: Video

by Tim Tscheblockov , Alexey Stepin , Anton Shilov

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

Anisotropic Filtering

Updated algorithms of anisotropic filtering and full-screen anti-aliasing implemented in RADEON X800 are all united under ATI’s SMOOTHVISION HD name.

ATI claims that RADEON X800 received an enhanced version of anisotropic filtering algorithm, which allows reducing the performance drop without losing any of the image quality. Moreover, during pixel by pixel subtraction of images obtained on RADEON 9800 XT and RADEON X800 XT Platinum Edition, there really appear a few insignificant differences, which get more evident on distanced MIP-levels. However, you will hardly be able to notice the differences between the pictures obtained on RADEON 9800 XT and RADEON X800 XT Platinum Edition.

So, in terms of anisotropic filtering implementation, ATI RADEON X800 will hardly offer us anything brand new: the anisotropic filtering algorithm has been fully transferred from R3x0, with a few minor changes. And the image quality differences between RADEON 9800 XT and RADEON X800 XT Platinum Edition we were talking about in the previous paragraph are really negligible.

However, in order to prove our point we would like to offer you a few screenshot fragments taken in 3DMark 03 during texture filtering quality tests.

At first let’s compare the quality of bi-linear filtering. On the left you see an image from ATI RADEON X800 XT Platinum Edition, and on the right – the image by ATI RADEON 9800 XT. The image in the lower left corner was taken on NVIDIA GeForce 6800 Ultra, while the very last image was taken from NVIDIA GeForce FX 5950 Ultra.

ATI RADEON X800 XT Platinum Edition, RADEON 9800 XT and NVIDIA GeForce FX 5950 Ultra show almost the same picture, while GeForce 6800 Ultra uses a different algorithm for LOD (Level Of Detail) calculations and hence provides somewhat lower texture clarity at the following angles: +/-45 and +/-135 degrees.

Now let’s pass over to tri-linear filtering. The settings in the drivers are set for maximum image quality, but the tri-linear filtering optimizations for GeForce 6800 haven’t been disabled, we will talk more about them later today.

So, the graphics cards were tested in the same order: ATI RADEON X800 XT Platinum Edition, RADEON 9800 XT, NVIDIA GeForce 6800 Ultra and NVIDIA GeForce FX 5950 Ultra.

You can see from the screenshots that the location of MIP-level borders remained unchanged, but the borders themselves turned into smooth color transitions due to tri-linear filtering algorithms and MIP-levels highlights. Graphics cards based on ATI graphics processors show a picture with fully-fledged tri-linear filtering, while the NVIDIA based solutions demonstrate images built as a combination of bi-linear and tri-linear filtering.