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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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  • arjuna1 - Monday, March 05, 2012 - link

    Metro 2033 (the highest settings bench)

    Radeon 7950 33fps
    Radeon 6970 27.5fps

    Radeon 6870 32fps (the second highest bench)

    Weee!!! $400+ for 5.5fps more.

    Not sure about you, but to me, spending that kind of cash for an imperceptible increase in performance is having no sense of money's worth.

    This generation of cards can safely be skipped until the 8xxx/7xx series from both AMD and NVIDIA.
    Reply
  • Death666Angel - Tuesday, March 06, 2012 - link

    Picking up one specific benchmark to underline your point. Great reasoning skills, you should join a debate team! Also, that 5.5fps is still 20%, with the good track record of overclockability, it can reach as much as 40%. But you stick to your point. Reply
  • arjuna1 - Tuesday, March 06, 2012 - link

    What? were you expecting me to post a powerpoint presentation for just for you??

    The numbers are there, look at them if you want, but hey, be stuck in your point, only a frustrated basement geek can think in way to justify spending $400 +/- for less than 50% increase in performance.

    Be careful of not falling of that horse, seems pretty high.
    Reply
  • sseemaku - Tuesday, March 06, 2012 - link

    Please check the avg frame rate improvements, not some specific results. But everyone agrees that 7xxx cards are a bit overpriced and that's because they don't have competition right now. If you worry about power consumption, buy these cards now. Or more interested in price/performance, wait till Kepler is released. Reply
  • arjuna1 - Tuesday, March 06, 2012 - link

    I can agree with that, after Kepler is release prices will go down and maybe then the 7xxx series will increase in the perceived value. Reply
  • CeriseCogburn - Thursday, March 08, 2012 - link

    If there's no competition then they aren't overpriced because they cannot be touched by anything, hence making their price absolutely correct !!!
    I call that "reality".
    If Kepler blows their doors off, their price will fall. That's reality too.
    It's time for all the amd is cheaper crud to go the way of the dinosaur.
    Recently a 460 was an unbeatable value. Then a 560ti was as unbeatable value. Currently a 6870 is an unbeatable value.
    These things happen, and a deal is not the general aspect of the video card prices, which generally speaking wind up right where they should be.
    The deal is the exception to the usual rule across the board, and "the deal" as in "big price drop" is usually just one card here or there for a short period of time.
    Reply
  • CeriseCogburn - Thursday, March 08, 2012 - link

    Radeon cards have been coming out at $700 and $600 and $500+ for a long time man - even with competition.
    I don't know what planet you people come from when the constant repetition of "it sounds good" becomes an absolute meme and ongoing restated theme but in no way reflects even a tiny kernel of truth as far as reality goes.
    Reply
  • CeriseCogburn - Friday, March 09, 2012 - link

    Yes dagamer34, Ryan praises amd for drying up their 6000 series channel with such precision. Then we get this praise - the perfect price structure by AMD, and "it's conservative pricing" according to the author even though it's $40 and $30 higher than it's Nvidia counterpart...
    " With AMD targeting the ~$320 570 and ~$210 560 Ti and given their conservative pricing on the rest of Southern Islands, it should come as no surprise that the 7800 series is priced equally conservatively. The 7870 will have an MSRP of $350, while the 7850 will have an MSRP of $250. With the 7800 series completing the launch of Southern Islands, this gives AMD a consistent price structure for the entire family: $550, $450, $350, $250, $159, and $109."
    ---
    I see. So more expensive is conservative, and the 6 AMD price figures are perfect and consistent...
    I am so sick of it...
    Reply
  • Falkenad2 - Monday, March 05, 2012 - link

    Thus far, AMD's first foray into 28nm graphics has been unimpressive. From a price/performance standpoint, the 7000 series has not given the usual incentives for upgrading that is regularly associated with the move to a new node. I hope a strong competitor from nVidia is on the way, as that would bode well for consumers such as ourselves. As it stands, the 7000 series lacks value except at the very high end, where price/performance is of little concern. Reply
  • Kaboose - Monday, March 05, 2012 - link

    Price vs. performance is not the only factor, some people are concerned with power draw as well. Others are interested in temps, and noise. The price could use some work (come on Nvidia) but besides that the 7xxx series has been fairly impressive in regards to overclocking, power, temp, and noise. Reply

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