The Return of Supersample AA

Over the years, the methods used to implement anti-aliasing on video cards have bounced back and forth. The earliest generation of cards such as the 3Dfx Voodoo 4/5 and ATI and NVIDIA’s DirectX 7 parts implemented supersampling, which involved rendering a scene at a higher resolution and scaling it down for display. Using supersampling did a great job of removing aliasing while also slightly improving the overall quality of the image due to the fact that it was sampled at a higher resolution.

But supersampling was expensive, particularly on those early cards. So the next generation implemented multisampling, which instead of rendering a scene at a higher resolution, rendered it at the desired resolution and then sampled polygon edges to find and remove aliasing. The overall quality wasn’t quite as good as supersampling, but it was much faster, with that gap increasing as MSAA implementations became more refined.

Lately we have seen a slow bounce back to the other direction, as MSAA’s imperfections became more noticeable and in need of correction. Here supersampling saw a limited reintroduction, with AMD and NVIDIA using it on certain parts of a frame as part of their Adaptive Anti-Aliasing(AAA) and Supersample Transparency Anti-Aliasing(SSTr) schemes respectively. Here SSAA would be used to smooth out semi-transparent textures, where the textures themselves were the aliasing artifact and MSAA could not work on them since they were not a polygon. This still didn’t completely resolve MSAA’s shortcomings compared to SSAA, but it solved the transparent texture problem. With these technologies the difference between MSAA and SSAA were reduced to MSAA being unable to anti-alias shader output, and MSAA not having the advantages of sampling textures at a higher resolution.

With the 5800 series, things have finally come full circle for AMD. Based upon their SSAA implementation for Adaptive Anti-Aliasing, they have re-implemented SSAA as a full screen anti-aliasing mode. Now gamers can once again access the higher quality anti-aliasing offered by a pure SSAA mode, instead of being limited to the best of what MSAA + AAA could do.

Ultimately the inclusion of this feature on the 5870 comes down to two matters: the card has lots and lots of processing power to throw around, and shader aliasing was the last obstacle that MSAA + AAA could not solve. With the reintroduction of SSAA, AMD is not dropping or downplaying their existing MSAA modes; rather it’s offered as another option, particularly one geared towards use on older games.

“Older games” is an important keyword here, as there is a catch to AMD’s SSAA implementation: It only works under OpenGL and DirectX9. As we found out in our testing and after much head-scratching, it does not work on DX10 or DX11 games. Attempting to utilize it there will result in the game switching to MSAA.

When we asked AMD about this, they cited the fact that DX10 and later give developers much greater control over anti-aliasing patterns, and that using SSAA with these controls may create incompatibility problems. Furthermore the games that can best run with SSAA enabled from a performance standpoint are older titles, making the use of SSAA a more reasonable choice with older games as opposed to newer games. We’re told that AMD will “continue to investigate” implementing a proper version of SSAA for DX10+, but it’s not something we’re expecting any time soon.

Unfortunately, in our testing of AMD’s SSAA mode, there are clearly a few kinks to work out. Our first AA image quality test was going to be the railroad bridge at the beginning of Half Life 2: Episode 2. That scene is full of aliased metal bars, cars, and trees. However as we’re going to lay out in this screenshot, while AMD’s SSAA mode eliminated the aliasing, it also gave the entire image a smooth makeover – too smooth. SSAA isn’t supposed to blur things, it’s only supposed to make things smoother by removing all aliasing in geometry, shaders, and textures alike.


8x MSAA   8x SSAA

As it turns out this is a freshly discovered bug in their SSAA implementation that affects newer Source-engine games. Presumably we’d see something similar in the rest of The Orange Box, and possibly other HL2 games. This is an unfortunate engine to have a bug in, since Source-engine games tend to be heavily CPU limited anyhow, making them perfect candidates for SSAA. AMD is hoping to have a fix out for this bug soon.

“But wait!” you say. “Doesn’t NVIDIA have SSAA modes too? How would those do?” And indeed you would be right. While NVIDIA dropped official support for SSAA a number of years ago, it has remained as an unofficial feature that can be enabled in Direct3D games, using tools such as nHancer to set the AA mode.

Unfortunately NVIDIA’s SSAA mode isn’t even in the running here, and we’ll show you why.


5870 SSAA


GTX 280 MSAA


GTX 280 SSAA

At the top we have the view from DX9 FSAA Viewer of ATI’s 4x SSAA mode. Notice that it’s a rotated grid with 4 geometry samples (red) and 4 texture samples. Below that we have NVIDIA’s 4x MSAA mode, a rotated grid with 4 geometry samples and a single texture sample. Finally we have NVIDIA’s 4x SSAA mode, an ordered grid with 4 geometry samples and 4 texture samples. For reasons that we won’t get delve into, rotated grids are a better grid layout from a quality standpoint than ordered grids. This is why early implementations of AA using ordered grids were dropped for rotated grids, and is why no one uses ordered grids these days for MSAA.

Furthermore, when actually using NVIDIA's SSAA mode, we ran into some definite quality issues with HL2: Ep2. We're not sure if these are related to the use of an ordered grid or not, but it's a possibility we can't ignore.


4x MSAA   4x SSAA

If you compare the two shots, with MSAA 4x the scene is almost perfectly anti-aliased, except for some trouble along the bottom/side edge of the railcar. If we switch to SSAA 4x that aliasing is solved, but we have a new problem: all of a sudden a number of fine tree branches have gone missing. While MSAA properly anti-aliased them, SSAA anti-aliased them right out of existence.

For this reason we will not be taking a look at NVIDIA’s SSAA modes. Besides the fact that they’re unofficial in the first place, the use of a rotated grid and the problems in HL2 cement the fact that they’re not suitable for general use.

Angle-Independent Anisotropic Filtering At Last AA Image Quality & Performance
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  • Zool - Friday, September 25, 2009 - link

    "The GT300 is going to blow this 5870 away - the stats themselves show it, and betting otherwise is a bad joke, and if sense is still about, you know it as well."
    If not than it would be a sad day for nvidia after more than 2 years of nothing.
    But the 5870 can still blow away any other card around. With DX11 fixed tesselators in pipeline and compute shader postprocessing (which will finaly tax the 1600 stream procesors)it will look much better than curent dx9. The main advantage of this card is the dx11 which of course nvidia doesnt hawe. And maybe the dewelopers will finaly optimize for the ati vector architecture if there isnt any other way meant to be played(payed) :).
    Actualy nvidia couldnt shrink the last gen to 40nm with its odd high frequency scalar shaders (which means much more leakage) so i wouldent expect much more from nvidia than double the stats and make dx11 either.
    Reply
  • SiliconDoc - Friday, September 25, 2009 - link

    Here more new NVidia cards, so the fasle 2 years complaint is fixzling fast.
    Why this hasn't been mentioned here at anadtech yet I'm not sure, but of course...

    http://www.fudzilla.com/content/view/15698/1/">http://www.fudzilla.com/content/view/15698/1/

    Gigabyte jumps the gun with 40nm

    According to our info, Nvidia's GT 220, 40nm GT216-300 GPU, will be officially announced in about three weeks time.

    The Gigabyte GT 220 works at 720MHz for the core and comes with 1GB of GDDR3 memory clocked at 1600MHz and paired up with a 128-bit memory interface. It has 48 stream processors with a shader clock set at 1568MHz.
    --
    See, there's a picture as well. So, it's not like nothing has been going on. It's also not "a panicky response to regain attention" - it is the natural progression of movement to newer cores and smaller nm processes, and those things take time, but NOT the two years plus ideas that spread around....
    Reply
  • SiliconDoc - Friday, September 25, 2009 - link

    The GT200 was released on June 16th and June17th, 2008, definitely not more than 2 years ago, but less.
    The 285 (nm die shrink) on January 15th, 2009, less than 1 year ago.

    The 250 on March 3rd this year, though I wouldn't argue you not wanting to count that.

    I really don't think I should have to state that you are so far off the mark, it is you, not I, that might heal with correction.

    Next, others here, the article itself, and the ati fans themselves won't even claim the 5870 blows away every other card, so that statement you made is wrong, as well.
    You could say every other single core card - no problem.
    Let's hope the game scenes do look much better, that would be wonderful, and a fine selling point for W7 and DX11 (and this casrd if it is, or remains, the sole producer of your claim).
    I suggest you check around, the DX11 patch for Battleforge is out, so maybe you can find confirmation of your "better looking" games.

    " Actualy nvidia couldnt shrink the last gen to 40nm with its odd high frequency scalar shaders "
    I believe that is also wrong, as they are doing so for mobile.
    What is true is ATI was the ginea pig for 40nm, and you see, their yeilds are poor, while NVidia, breaking in later, has had good yeilds on the GT300, as stated by - Nvidia directly, after ATI made up and spread lies about 9 or less per wafer. (that link is here, I already posted it)
    ---
    If Nvidia's card doubles performance of the 285, twice the frames at the same reso and settings, I will be surprised, but the talk is, that or more. The stats leaked make that a possibility. The new MIMD may be something else, I read 6x-15x the old performance in certain core areas.
    What Nvidia is getting ready to release is actually EXCITING, is easily described as revolutionary for videocards, so yes, a flop would be a very sad day for all of us. I find it highly unlikely, near impossible, the silicon is already being produced.
    The only question yet is how much better.
    Reply
  • Zool - Friday, September 25, 2009 - link

    I want to note also that the 5870 is hard to find which means the 40nm tsmc is still far from the last gen 55nm. After they manage it to get on the 4800 level the prices will be different. And maybe the gt300 is still far away. Reply
  • mapesdhs - Friday, September 25, 2009 - link


    Is there any posting moderation here? Some of the flame/troll posts
    are getting ridiculous. The same thing is happening on toms these days.

    Jarred, best not to reply IMO. I don't think you're ever going to get
    a logical response. Such posts are not made with the intent of having
    a rational discussion. Remember, as Bradbury once said, it's a sad
    fact of nature that half the population have got to be below average. :D

    Ian.


    Reply
  • Zool - Friday, September 25, 2009 - link

    I would like to see some more tests on power load. Actualy i dont think there are too many people with 2560*1600 displays. There are still plenty people with much lower resolutions like 1680*1050 and play with max imagequality. With VSync on if u reduce 200fps to 60fps u get much less gpu temps and also power load.(things like furmark are miles away from real world) On LCD there is no need to turn it off just if u benchmark and want more fps. I would like to see more power load tests with diferent resolutions and Vsync on.(And of course not with crysis)
    Also some antialiasing tests, the adaptive antialiasing on 5800 is now much faster i read.And the FSAA is of course blurry, it was always so. If u render the image in 5120*3200 on your 2560*1600 display and than it combines the quad pixels it will seems like its litle washed out. Also in those resolution even the highress textures will begin to pixalate even in closeup so the combined quad pixels wont resemble the original. Without higher details in game the FSAA in high resolution will just smooth the image even more. Actualy it always worked this way even on my gf4800.

    Reply
  • SiliconDoc - Friday, September 25, 2009 - link

    PS - a good friend of mine has an ATI HD2900 pro with 320 shaders (a strange one not generally listed anywhere) that he bought around the time I was showing him around the egg cards and I bought an ATI card as well.
    Well, he's a flight simmer, and it has done quite well for him for a about a year, although in his former Dell board it was LOCKED at 500mhz 503mem 2d and 3d, no matter what utility was tried, and the only driver that worked was the CD that came with it.
    Next on a 570 sli board he got a bit of relief, an with 35 various installs or so, he could sometimes get 3d clocks to work.
    Even with all that, it performed quite admirably for the strange FS9 not being an NVidia card.
    Just the other day, on his new P45 triple pci-e slot, after 1-2 months running, another friend suggested he give OCCT a go, and he asked what is good for stability (since he made 1600fsb and an impressive E4500 (conroe) 200x11/2200 stock to a 400x8/ 3200mhz processor overclock for the past week or two). "Ten minutes is ok an hour is great" was the response.
    Well, that HD2900pro and OCCT didn't like eachother much either - and DOWN went the system, 30 seconds in, cooking that power supply !
    --- LOL ---
    Now that just goes to show you that hiding this problem with the 4870 and 4890 for so many months, not a peep here... is just not good for end users...
    ---
    Thanks a lot tight lipped "nothing is wrong with ATI cards" red fans. Just wonderful.
    ---
    He had another PS and everything else is OK

    , and to be quite honest and frank and fair as I near always am, that HD2900pro still does pretty darn good for his flight simming ( and a few FPS we all play sometimes) and he has upgraded EVERYTHING else already at least once, so on that card, well done for ATI. (well depsite the drivcer issues, 3d mhz issues, etc)
    Oh, and he also has a VERY NICE 'oc on it now(P45 board) - from 600/800 core/mem 3D to 800/1000, and 2d is 500/503, so that's quite impressive.
    Reply
  • SiliconDoc - Wednesday, September 30, 2009 - link

    Ahh, isn't that typical, the 3 or 4 commenters raving for ati "go dead silent" on this furmark and OCCT issue.
    --
    "It's ok we never mentioned it for a year plus as we guarded our red fan inner child."
    (Ed. note: We "heard" nvidia has a similar implementation")
    WHATEVER THAT MEANS !
    ---
    I just saw (somewhere else) another red fanatic bloviating about his 5870 only getting up to 76C in Furmark. ROFLMAO
    --
    Aww, the poor schmuck didn't know the VRM's were getting cut back and it was getting throttled from the new "don't have a heat explosion" tiny wattage crammed hot running ati core.
    Reply
  • SiliconDoc - Friday, September 25, 2009 - link

    Well you brought to mind another sore spot for me.
    In the article, when the 4870 and 4890 FAIL furmark and OCCT, we are suddenly told, after this many MONTHS, that a blocking implementation in ati driver version 9.2 was put forth by ATI, so their cards wouldn't blow to bits on furmark and OCCT.
    I for one find that ABSOLUTELY AMAZING that this important information took this long to actually surface at red central - or rather, I find it all too expected, given the glaring bias, ever present.
    Now, the REASON this information finally came forth, other thanb the epic fail, is BECAUSE the 5870 has a "new technology" and no red fan site can possibly pass up bragging about something new in a red core.
    So the brag goes on, how protection bits in the 5870 core THROTTLE BACK the VRM's when heat issues arise, hence allowing for cheap VRM's & or heat dissipation issues to divert disaster.
    That's wonderful, we finally find out about ANOTHER 4870 4980 HEAT ISSUE, and driver hack by ATI, and a failure to RUN THE COMMON BENCHMARKS we have all used, this late in the game.
    I do have to say, the closed mouthed rabid foam contained red fans are to appluaded for their collective silence over this course of time.
    Now, further bias revealed in tha article - the EDITOR makes sure to chime in, and notes ~"we have heard Nvidia has a similar thing".
    What exactly that similar thing is, and whom the Editor supposedly heard it from, is never made clear.
    Nonetheless, it is a hearty excuse and edit for, and in favor of, EXCUSING ATI's FAILURES.

    Nonetheless, ALL the nvidia cards passed all the tests, and were 75% in number to the good cooler than the ATI's that were- ATI all at 88C-90C, but, of course, the review said blandly in a whitewash, blaming BOTH competitors nvidia and ati - "temps were all over the place" (on load).
    (The winning card GTX295 @ 90C, and 8800GT noted 92C *at MUCH reduced case heat and power consumption, hence INVALID as comparison)
    Although certain to mention the GT8800 at 92C, no mention of the 66C GTX250 or GTX260 winners, just the GTX275 @ 75C, since that was less of a MAJOR EMBARRASSMENT for the ATI heat load monsters !
    Now THERE'S A REAL MONSTER - AND THAT'S ALL OF THE ATI CARDS TESTED IN THIS REVIEW ! Not just the winning nvidia, while the others that matter (can beat 5870 in sli or otherwise) hung 24C to 14C lower under load.
    So, after all that, we have ANOTHER BIAS, GLARING BIAS - the review states " there are no games we know of, nor any we could find, that cause this 5870 heat VRM throttling to occur".
    In other words, we are to believe, it was done in the core, just for Furmark and OCCT, or, that it was done as precaution and would NEVER come into play, yes, rest assured, it just won't HAPPEN in the midst of a heavy firefight when your trigger finger is going 1,000mph...
    So, I found that just CLASSIC for this place. Here is another massive heat issue, revealed for the first time for 4870 and 4890 months and months and months late, then the 5870 is given THE GOLDEN EXCUSE and massive pass, as that heat reducing VRM cooling voltage cutting framerate lowering safety feature "just won't kick in on any games".
    ROFL
    I just can't help it, it's just so dang typical.
    Reply
  • DigitalFreak - Friday, September 25, 2009 - link

    Looks like SnakeOil has yet ANOTHER account. Reply

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