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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
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  • CeriseCogburn - Thursday, March 08, 2012 - link

    Yet if one is not running gigantic resolutions, they look at the usual, 1920 and 1650 p resolutions, and likely want to crank all the eye candy to the limit, which is still IMPOSSIBLE at those common resolutions with 60+ frames in so many of the popular games.
    So the real problem is you go from "can't do it all" to "still can't do it all" but at least you've got 40 frames going to 55 on your one screen... with maybe one more setting of 7 at ultra...
    ---
    For others with 3x 2560 most of us really don't give a crap if they claim they get 2x frames - because if they don't have 2 or 3 or 4 of them running, they are stuck in turn down the eye candy crapsville TOO.
    --
    We almost always hear that we are stuck with console ports, the exact opposite of the real truth in the real problem.
    A 570 is NOT ENOUGH, a 7870 is not either, nor is a 7970 for 1900x1200.
    IT'S NOT GOOD ENOUGH.
    Reply
  • SlyNine - Thursday, March 08, 2012 - link

    75% was wrong, but so is 70-110% faster.

    Crysis 2560x1600 at the MAX settings its 20 vx 33, which is just over 60%

    Drop down to 1920x1200 at the advantage drops to 50%.

    Metro its 60% at max res/settings (36vs22.5)

    Drop that down to 1920X1200 and its just over 50%

    Dirt 3 its just over 50% at max res/settings Drop that down to 1920x1200 and its remains just above 50% ( 104 vs 68.4)

    Battlefield 3 its 50% (49.7 vs 32.6) at max settings/res.

    So where the heck are you getting 70% to 110% ??

    2 1/2 years ago I payed around 66% of your price, and I'm getting 66% of your performence, ALMOST 3 YEARS. THIS IS NOT MOVING THINGS FORWARD
    Reply
  • CeriseCogburn - Thursday, March 08, 2012 - link

    Get back to us krummer when the 7870 is "released" and has "stable drivers" that "work most of the time" in "most of the games" and the IQ cheats of 10% driver default plus ever more now with this new blur job called MLAA and the lack of LOD bias up high enough that "in the case of SSAA" it's another low detail IQ cut down, not to mention other things like PhysX and tessellation above 10 all the way to 32...the other "unneeded" "eye candy" that "sucks" because amd sucks at doing it.
    *
    9% , minus 10% standardized cheat, minus SSAA LOD bias cheat, minus MLAA blur cheat, minus PhysX, minus 8 other things I won't take time to mention doesn't sound like "faster" to me.
    I mean come on, if the arch is so superior, why all the hack and cheats and crappy blurring and lack of features ?
    Are the drivers going to be another ongoing nightmare for 47% of all ibm pc implementations ?
    Reply
  • chizow - Monday, March 05, 2012 - link

    @ Kiste: Agreed.

    The "competition is necessary" meme needs to die in the tech sector because it isn't necessary.

    Most of this stuff doesn't expire or die on its own, not before it becomes obsolete anyways and in order for it to become obsolete there needs to be innovation and performance increases.

    That's what drives innovation with technology and it certainly exists without competition.
    Reply
  • medi01 - Monday, March 05, 2012 - link

    What are you talking about, considering AMD 7850 is faster in most tests than nVidia's 80$ more expensive 570, at the same time consuming 25% less energy. Reply
  • Malih - Monday, March 05, 2012 - link

    I think this is the decision of the new management, they decide to price something that performs better to price higher.

    Probably will drop the price in the future, but it would require a new release from nVidia with agressive pricing. It is rumored nVidia will release new cards near the end of March.
    Reply
  • biassj - Monday, March 05, 2012 - link

    Shitty pricing again, if the pricing was 50 bucks cheaper I would probably consider buying 7870 or 7950 at this moment. These high prices will just have me wait to see what Nvidia has to offer. Reply
  • piroroadkill - Monday, March 05, 2012 - link

    Huh, I thought it was GTX 570 class for less.

    Seems solid enough.
    Reply
  • piroroadkill - Monday, March 05, 2012 - link

    For the 7850, I mean. Reply
  • chizow - Monday, March 05, 2012 - link

    This pricing isn't nearly as bad as the 7770 or 7950/7970, but its still pretty poor overall given it once again, slides right in to existing price structures offering very little incentive to upgrade and very little price performance value compared to what has been available for 14+ months. Reply

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