ATI's Optimized Texture Filtering Called Into Question

Brilinear - Simply Filter Less, Continued

A few benchmarks follow that show how much performance can be gained from a brilinear optimization.

The GeForce 6800 Ultra shows the same result with and without colored mipmaps, with trilinear optimizations modes ON and OFF. The X800, however, gains a lot of performance without colored mipmaps. Keep in mind that not all areas in this mode are covered by the colored mipmaps, so the real delta should be even bigger!

You have to remember that with colored mipmaps, there are still some places that are not colored. ATI driver still optimizes those textures. This means that the delta between full filtering and optimized filtering of the X800 must be even greater than the results with colored mipmaps show.

ATI apologizes for the failure to explain this by saying that an application has been filed for patent protection of the adaptive technology, and they thus cannot discuss it. However, there is no way of checking how much truth there is to this.

It is more significant that in its white papers, ATI leaves one with the impression that full trilinear filtering is being offered, and calls on reviewers to switch off competitors' trilinear filtering - read GeForce 6800 - to ensure a "fairer" comparison. At the same time, they are called on to assess the image quality of the X800 by means of tests with colored mipmaps - but at that precise moment the driver provides a filter quality that is not offered in games.

In one of the Radeon X800 reviewer guides, ATi claims to offer full trilinear filtering and suggests using standard image quality tools with colored mipmaps to prove it - what is impossible and not true, as we know now.

"To ensure a fair comparison...." ATi suggests disabling the NVIDIA Trilinear optimization and force the GeForce 6800 Ultra to full trilinear - although the X800 is not able to do full trilinear filtering with current drivers.

From the ATi benchmarking presentation during Editors Day2 in Toronto. ATi speaks of reducing trilinear to bilinear but it was pretty clear that ATi meant the brilinear optimization in NVIDIAs GeForce 5xxx series. ATis marketing team always spoke of bilinear filtering for those cards. No vendor reduces trilinear to full bilinear... yet.