High Quality AF

One of the greatest things about the newest high end hardware from NVIDIA and ATI is that advanced filtering features can be enabled at any resolution while still maintaining playable framerates. It may take developers a little while to catch up to the capabilities of the X1800 and 7800 lines, but adding value through advanced quality features is definitely a welcome path for ATI and NVIDIA to take. For this launch, ATI has improved their AA and AF implementations. We also have two brand new features: Adaptive AA and Area Anisotropic filtering.

Starting with Area Anisotropic (or high quality AF as it is called in the driver), ATI has finally brought viewing angle independent anisotropic filtering to their hardware. NVIDIA introduced this feature back in the GeForce FX days, but everyone was so caught up in the FX series' abysmal performance that not many paid attention to the fact that the FX series had better quality anisotropic filtering than anything from ATI. Yes, the performance impact was larger, but NVIDIA hardware was differentiating the Euclidean distance calculation sqrt(x^2 + y^2 + z^2) in its anisotropic filtering algorithm. Current methods (NVIDIA stopped doing the quality way) simply differentiate an approximated distance in the form of (ax + by + cz). Math buffs will realize that the differential for this approximated distance simply involves constants while the partials for Euclidean distance are less trivial. Calculating a square root is a complex task, even in hardware, which explains the lower performance of the "quality AF" equation.

Angle dependant anisotropic methods produce fine results in games with flat floors and walls, as these textures are aligned on axes that are correctly filtered. Games that allow a broader freedom of motion (such as flying/space games or top down view games like the sims) don't benefit any more from anisotropic filtering than trilinear filtering. Rotating a surface with angle dependant anisotropic filtering applied can cause noticeable and distracting flicker or texture aliasing. Thus, angle independent techniques (such as ATI's area aniso) are welcome additions to the playing field. As NVIDIA previously employed a high quality anisotropic algorithm, we hope that the introduction of this anisotropic algorithm from ATI will prompt NVIDIA to include such a feature in future hardware as well.

We sat down with the D3DAFTester to show the difference between NVIDIA and ATI hardware with and without the high quality mode enabled. Here's what we ended up with:

NVIDIA 7800 GTX AF

NVIDIA 7800 GTX AF

Mouse over to cycle images

High Quality AF does come with a performance hit. We tested Far Cry at 1600x1200 on a Radeon X1800 XL and saw a performance drop from 76.3 fps to 71.2 fps. This is quite acceptable on high end hardware, but may not be a viable option for everyone.
Memory Architectures Adaptive AA
Comments Locked

103 Comments

View All Comments

  • TinyTeeth - Wednesday, October 5, 2005 - link

    Oh, I had completely ignored that one because I heard something about their graphs being horrible and hard to read. But I'll take a look at it, thanks!
  • TinyTeeth - Wednesday, October 5, 2005 - link

    And now I remember it was PC Perspective that had the horrible graphs.

    Sorry, my head isn't working properly today, I'm afraid. :(
  • fishbits - Wednesday, October 5, 2005 - link

    Maybe a late, light review was supposed to be a witty jab at ATI? :P
  • hotdog453 - Wednesday, October 5, 2005 - link

    I agree. But, some review sites are still touting Quake3 as a benchmark for some components (mainly CPUs now, but still)... they use games that stress the component well, not really the games you and I may be playing. Kind of ironic, I know.

    Honestly, when was the last time any of us fired up Doom3, except to benchmark something? It was a horrible game. Simply horrible. Scripted events do not a good game make. But from a technical, omg, point of view, it made cards cry. So they use it *shrug*

  • Madellga - Wednesday, October 5, 2005 - link

    Is that right? Or the titles were wrongly exchanged?
  • hoppa - Wednesday, October 5, 2005 - link

    Am I missing something here? The article states that the hardware is quite powerful and a good deal, yet to me the benchmarks look absolutely miserable. The X1ks are on the bottom of nearly every chart, and in some cases, even lower than their predecessors (X800)! What the hell!
  • JarredWalton - Wednesday, October 5, 2005 - link

    Actually, the conclusion states that the hardware appears quite powerful - especially the X1800 XT - but that the price is too high. I saw several places where the article comments on price, so if you got the impression that it's a "good deal" let me know where and I'll edit it. :)
  • Madellga - Wednesday, October 5, 2005 - link

    On the high end comparison - Day of Defeat, it is missing the X1800XT performance bar.
  • Madellga - Wednesday, October 5, 2005 - link

    For the 1600x1200 chart...
  • JarredWalton - Wednesday, October 5, 2005 - link

    Fixed - it was 59.5 FPS, if you read the text.

Log in

Don't have an account? Sign up now