AMD Radeon 6000 Series Image Quality Analysis
MLAA (Morphological Anti-Aliasing)
Morphological Anti-Aliasing is a feature introduced with the 6000 series which now works on the 5000 series as of the 10.10e hotfix driver. It is implemented by DirectCompute shaders so in theory it could be implemented on any video card that has high enough shader capabilities. MLAA replaces the narrow and wide tent CFAA modes so these have been removed from the control panel, though it’s possible they can still be activated by third party utilities.
MLAA is similar to CFAA in that it’s a shader based post-filter, but it happens much later in the pipeline, after all of the rendering has finished. It works by detecting certain patterns in the final rendered scene and blending them together according to their shape, introducing intermediate colors into image discontinuations. MLAA can be combined with regular AA which results in the post-filter being applied on top of the existing AA, along with a combined performance hit.
MLAA’s advantages over traditional AA are that it’s theoretically compatible with every game (including deferred renderers), and it doesn’t use additional VRAM since the scene is not rendered higher. It’s also supposed to be faster than regular AA, though performance tests later in this article reveal this is often not the case.
Its disadvantages are that it only reuses pixel-level data from a finished frame, and as a result it doesn’t have access to any higher precision sub-pixel information. Also unlike edge-detect CFAA which only blends polygon edges, MLAA can blend anywhere which can cause scene blurring and loss of detail.
As it operates on finished images MLAA cannot be captured by Fraps, though games that implement in-game screen captures will show it. AMD provides a tool to apply MLAA to finished images but I found it easier to use Radeon Pro, which has the ability to capture MLAA images. I can confirm the screenshots below match what I was seeing in-game:
4xMSAA
4xSSAA
MLAA
The images above are a hut from Far Cry 1. Compared to MSAA/SSAA, MLAA has visibly worse edges on the top and left edges of the hut’s roof, and also on the large diagonal beam below it. Also the inside of the hut’s roof is visibly smudged from excessive blurring. The top chair and crate edges are smoother with MLAA, however.
In Far Cry 1 MLAA also causes edges at long distances to sparkle even without player movement. The algorithm seems to be constantly changing its mind about how to anti-alias things, which leads to inconsistent image quality when gaming.
I tried MLAA in about a dozen games including ones where AA doesn’t normally work, such as Timeshift, Halo 1 and Cryostasis. While it worked everywhere, almost every game had obvious blurring to 3D scenes, menus and text; console text in Half-Life 2 was practically unreadable. MLAA also showed little to no improvement to shader and vegetation aliasing during in-game movement in games like Far Cry 2 and Crysis. It just blurred the vegetation without really doing much to reduce the shimmering.
About the only game where MLAA provided acceptable image quality was in Halo 1 where it visibly reduced jagged edges without excessive blurring.
After looking at those images for a long time my head hurts *dizzy*
Great article.
Although “Both vendors degrade image quality at default driver settings” may sound a bit missleading. Because AMD lowered default IQ historicaly speaking. I mean compared to previous drivers and previous cards.
ysondurr, the comment referred to the fact that both vendors’ image quality increases when running HQ compared to their default settings.
excellent review
i’m translating another article from Rage3D regarding the same subject – image quality comparision between AMD & NVIDIA’s latest graphics. i read both articles, they are both great but i still feel something lacks. besides the AA & AF and few zoomed game image comparision, i think it better to add more games to compare the overall image feeling. because there are a lot of arguments in my country stating that AMD provides much better image quality in both games and video-playback than nVidia. but for my personal experience i think nVidia graphics provide much more natural images. so i search the web and found Rage3D’s article last month and translating it. haven’t finished the translation due to recently increased payload in work. the AA & AF quality comparision would be a great proof to “who’s better”, but people will have another quesion. it seems that sometimes AMD offers a more colorful image while nVidia’s is a bit flat, is this a type of image quality issue? i read some reviews but they never regard this as an image quality issue. however people in my country think it as an image quality issue. what’s your opinion dear Mr. BFG10K?
and finally, can i put this article in my translation works?
thx
kiss4luna,
Though I’ve seen many such claims over the years, I’ve never seen any evidence of this so called “extra vibrance”, aside from nVidia’s old digital vibrance setting. In 3D gaming the colors have always looked identical to me with both vendors. I think it’s a placebo effect similar to how some individuals keep stating that each new driver is “smoother” and has “better IQ” than the old one when in reality nothing has changed.
Feel free to translate the article but give full linkage and credit to ABT. We want the traffic coming here.
Thank you, BFG10K. You have my words 😉
What I find surprising is that you haven’t noticed that the 470 can’t render a circle!
Real Life, the term for the circle is “angle invariance”, and I mention it several times in my article.
I don’t recall AMD ever claiming MLAA to be faster than MSAA. I do recall them saying it offers performance that of edge detect aka CFAA.
If you reviewed this with the thought that MLAA was intended to be an end all AA feature, then you have the wrong mind set and your conclusion is going to reflect that.
In my finding thus far, it works brilliantly in games with half AA or no AA(differed render’s) AND with a limited color spectrum. High contrast color edges will give a nasty result like many of the games you tested.
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