• What
    is this?
    You've landed on the AMD Portal on AnandTech. This section is sponsored by AMD. It features a collection of all of our independent AMD content, as well as Tweets & News from AMD directly. AMD will also be running a couple of huge giveaways here so check back for those.
    PRESENTED BY

Further Image Quality Improvements: SSAA LOD Bias and MLAA 2.0

The Southern Islands launch has been a bit atypical in that AMD has been continuing to introduce new AA features well after the hardware itself has shipped. The first major update to the 7900 series drivers brought with it super sample anti-aliasing (SSAA) support for DX10+, and starting with the Catalyst 12.3 beta later this month AMD is turning their eye towards further improvements for both SSAA and Morphological AA (MLAA).

On the SSAA side of things, since Catalyst 9.11 AMD has implemented an automatic negative Level Of Detail (LOD) bias in their drivers that gets triggered when using SSAA. As SSAA oversamples every aspect of a scene – including textures – it can filter out high frequency details in the process. By using a negative LOD bias, you can in turn cause the renderer to use higher resolution textures closer to the viewer, which is how AMD combats this effect.

With AMD’s initial release of DX10+ SSAA support for the 7900 series they enabled SSAA DX10+ games, but they did not completely port over every aspect of their DX9 SSAA implementation. In this case while there was a negative LOD bias for DX9 there was no such bias in place for DX10+. Starting with Catalyst 12.3 AMD’s drivers have a similar negative LOD bias for DX10+ SSAA, which will bring it fully on par with their DX9 SSAA implementation.

As far as performance and image quality goes, the impact to both is generally minimal. The negative LOD bias slightly increases the use of higher resolution textures, and thereby increases the amount of texels to be fetched, but in our tests the performance difference was non-existent. For that matter in our tests image quality didn’t significantly change due to the LOD bias. It definitely makes textures a bit sharper, but it’s a very subtle effect.


Original uncropped screenshots

4x SSAA 4x SSAA w/LOD Bias

Moving on, AMD’s other AA change is to Morphological AA, their post-process pseudo-AA method. AMD first introduced MLAA back in 2010 with the 6800 series, and while they were breaking ground in the PC space with a post-process AA filter, game developers quickly took the initiative 2011 to implement post-process AA directly into their games, which allowed it to be applied before HUD elements were drawn and avoiding the blurring of those elements.

Since then AMD has been working on refining their MLAA implementation, which will be replacing MLAA 1.0 and is being launched as MLAA 2.0. In short, MLAA 2.0 is supposed to be faster and have better image quality than MLAA 1.0, reflecting the very rapid pace of development for post-process AA over the last year and a half.

As far as performance goes the performance claims are definitely true. We ran a quick selection of our benchmarks with MLAA 1.0 and MLAA 2.0, and the performance difference between the two is staggering at times. Whereas MLAA 1.0 had a significant (20%+) performance hit in all 3 games we tested, MLAA 2.0 has virtually no performance hit (<5%) in 2 of the 3 games we tested, and in the 3rd game (Portal 2) the performance hit is still reduced by some. This largely reflects the advancements we’ve seen with games that implement their own post-process AA methods, which is that post-process AA is nearly free in most games.

Radeon HD 7970 MLAA Performance
  4x MSAA 4x MSAA + MLAA 1.0 4x MSAA + MLAA 2.0
Crysis: Warhead 54.7

43.5

53.2
DiRT 3 85.9 49.5 78.5
Portal 2 113.1 88.3 92

As for image quality, that’s not quite as straightforward. Since MLAA does not have access to any depth data and operates solely on the rendered image, it’s effectively a smart blur filter. Consequently like any post-process AA method there is a need to balance the blurring of aliased edges with the unintentional burring of textures and other objects, so quality is largely a product of how much burring you’re willing to put up for any given amount of de-aliasing. In other words, it’s largely subjective.


Original uncropped screenshots

  Batman AC #1 Batman AC #2 Crysis: Warhead Portal 2
MLAA 1.0 Old MLAA Old MLAA Old MLAA Old MLAA
MLAA 2.0 New MLAA New MLAA New MLAA New MLAA

From our tests, the one thing that MLAA 2.0 is clearly better at is identifying HUD elements in order to avoid blurring them – Portal 2 in particular showcases this well. Otherwise it’s a tossup; overall MLAA 2.0 appears to be less overbearing, but looking at Portal 2 again it ends up leaving aliasing that MLAA 1.0 resolved. Again this is purely subjective, but MLAA 2.0 appears to cause less image blurring at a cost of less de-aliasing of obvious aliasing artifacts. Whether that’s an improvement or not is left as an exercise to the reader.

Meet The Radeon HD 7870 & Radeon HD 7850 The Test
POST A COMMENT

173 Comments

View All Comments

  • Taft12 - Monday, March 05, 2012 - link

    Or don't. It's not on sale for 2 weeks yet. Reply
  • MySchizoBuddy - Monday, March 05, 2012 - link

    NOT with 1/16 the FP64 performance. Reply
  • Zoomer - Wednesday, March 07, 2012 - link

    FP64 is useless for games for the foreseeable future. Reply
  • CeriseCogburn - Thursday, March 08, 2012 - link

    I love the "further image quality improvements page" which delicately and carefully explains how amd did a wonderful job of making things better as the image quality degrades...
    After noting the degredation very, very lightly and tossing out the problem, it is declared "unnoticable" for "all intents and purposes".
    Eventually amd's IQ is going to be so far behind nvidia's the endless denials and it doesn't matters - will just continue since amd can crank an extra 20 fps doing it...
    LOL
    A "gift" from amd.
    Reply
  • MySchizoBuddy - Monday, March 05, 2012 - link

    where is the double precision compute benchmarks Reply
  • CeriseCogburn - Friday, March 09, 2012 - link

    Article: " As AMD began winding down Cayman (6900 series) almost immediately with the launch of the 7900 series, at this point the 6900 market has effectively dried up. Having taken themselves out of competition with themselves, AMD’s only competition is NVIDIA’s lineup."
    --
    And there we have it - AMD and their evil plot to squeeze every last dollar out of those "they care about", the gamers...
    I don't want to hear Nvidia is evil anymore.
    Time to look in the mirror amd users.
    --
    Furthermore, it's time the reviewers start slamming AMD the way they slam Nvidia, in this case, one can consider it PRAISE for AMD "drying up their own card channels"- and if that isn't bias I don't know what is.
    Reply
  • dagamer34 - Monday, March 05, 2012 - link

    These cards don't seem like such a wonderful value considering what the 6900 series was offering, but since those cards have gone poof, I guess you'll have to settle for the 7800 series? It really just seems like they are adjusting their pricing scheme to be less compressed than it was before.

    TL: DR; If you've got a 6900 series card, the 7000 series is not for you.
    Reply
  • Jedi2155 - Monday, March 05, 2012 - link

    I still have my wonderful 5870 I purchased in 2009 (which now is not far from 3 years ago...), and still waiting for something that offers more performance than the 7970. Com'on Nvidia! Blow everything out of the water please.... Reply
  • Death666Angel - Monday, March 05, 2012 - link

    "TL: DR; If you've got a 6900 series card, the 7000 series is not for you."
    I'd say the 30 to 50% increase of the 79xx to 69xx cards could be well worth it. However, unless you run a multi-monitor setup or have a 2560 resolution, you really should think twice about spending that amount of money on these cards. But I guess people with that kind of cash can either do their own thinking or don't have to care too much about spending and can afford to "BUY ALL THE CARDS".
    I'm still running a HD5770 and have a newly acquired 27" monitor here that is really stressing it. I think I'll go for a 78xx and later upgrade to CF because my 550W PSU can handle it with these cards, whereas HD69xx would be stressing it too much. :-)
    Reply
  • cactusdog - Monday, March 05, 2012 - link

    "TL: DR; If you've got a 6900 series card, the 7000 series is not for you."

    Thats the dumbest statement I have ever read here. The 7970 is DOUBLE the performance of the 6970 with overclocking. Even the $250 7850 beats the 6970 with overclocking.

    The 7 series is the biggest performance jump over the previous series since I have followed graphics cards, since 1998.
    Reply

Log in

Don't have an account? Sign up now