ATI's Optimized Texture Filtering Called Into Question

Introduction

ATI is cheating on trilinear texture filtering with the new X800, according to posts in Internet forums. Others ardently defend ATI. The heated discussions are fatally reminiscent of the cries of "cheater" that rang out last year against NVIDIA.

An article on the German Website Computerbase triggered the discussion. The article showed how ATI uses an optimized trilinear texture filtering, often dubbed "brilinear" - i.e. a mixture of bilinear and trilinear - in the Radeon 9600 graphics processor and in the X800 graphics chip based on this architecture. This was news, since ATI always claimed to provide true trilinear filtering.

But what is really going on here? Optimization, cheating or, ultimately, an incredibly clever solution? In order to tell, some fundamental knowledge of the various filtering techniques is needed. That's why first we take a somewhat oversimplified look at the different texture filtering techniques - oversimplified because the precise procedure can hardly be summed up in a couple of pages. Here, we just take a look at the basics and principle functions.

This comparison clearly demonstrates how proper filtering improves the image quality.