Trilinear Filtering: Fast and Furious

We first touched upon the problem of texture filtering quality as provided by today’s graphics cards from ATI and Nvidia in our review of the ATI Radeon X1950 XTX. We found out that ATI’s solutions indeed delivered texture filtering of a higher quality but you could only see that in motion. It’s hard, if not altogether impossible, to spot the difference by comparing static images.

To show you the difference between the tri-linear filtering levels available on Nvidia’s GeForce cards, we took screenshots under ideal conditions: in 3DMark03 with enabled mip-levels highlighting.

ATI Radeon X1950 XTX vs. Nvidia GeForce 7950 GX2 Trilinear Filtering Comparison
ATI Radeon X1950 XTX, Catalyst AI: Advanced	ATI Radeon X1950 XTX, Catalyst AI: Standard	ATI Radeon X1950 XTX, Catalyst AI: Disabled
	Nvidia GeForce 7950 GX2, Texture Filtering: Quality	Nvidia GeForce 7950 GX2, Texture Filtering: High Quality

You can see that in the Quality mode with enabled optimizations GeForce 7 series cards perform a greatly simplified filtering which looks more like a combination of bi-linear and anisotropic filtering than the classic mix of tri-linear and anisotropic filtering. There is no smoothness in the transitions between the mip-levels. This leads to the characteristic texture flickering in games and “volatile” borders of levels that you can see in motion.

The High Quality mode automatically disables the optimizations and greatly improves the quality of filtering. In this case, cards from ATI and Nvidia produce similar-looking images, although the tri-linear filtering algorithm from ATI still delivers a somewhat higher quality. It’s not because the algorithm is better. ATI’s driver just analyzes the scene and, basing on the results of the analysis, performs a more complex or simpler tri-linear filtering as necessary. This leads to an ideal tri-linear filtering as you can see when the mip-levels are highlighted. So, formally speaking, ATI offers a higher tri-linear filtering quality, but we’ll see from the following clips how things stand in practice.

• Battlefield 2 movie (download here)
• Half-Life 2 movie 1 (download here)
• Half-Life 2 movie 2 (download here)

In the High Quality mode, there is no more texture flickering on Nvidia cards. The transitions between mip-levels are now not as sharp as before. As you can see, the quality of tri-linear filtering is roughly the same on ATI’s Radeon X1000 and Nvidia’s GeForce 7 cards. It’s hard to tell who’s the leader here.