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Trying to learn about FXAA

By Dawn1113
Jun 10, 2012
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  1. I've been trying to read up on FXAA. The stuff I've found online, however, either do not say much or contain technical jargon which are beyond me.

    Is FXAA meant as an alternative to MSAA or an enhancement ? Nvidia compares FXAA to MSAA as though it were something you would use in place of the former. But I seem to get better results when I use a combination of both -- lowering in-game MSAA with FXAA enabled. I'm not even sure that's a valid route, though -- one may cancel out the other, for all I know.

    Also,Where do you I find FXAA control settings in the Nvdia control panel? Can I set it to high or low? Do I need to download Nvidia Inspector for that?

    Do any of you guys use FXAA? If so, how have you configured your settings? I'm keen to know what your impressions are as to the AA quality it offers and the kind of performance you're getting with it enabled.

    I apologize for what must be an annoying barrage of noob questions.

    Thanks in advance for your help.
  2. slh28

    slh28 TechSpot Paladin Posts: 1,925   +170

    Well first off, FSAA (full screen) is probably the easiest to understand: If your resolution is 1920x1080 then it will take a 3840x2160 image (for example) and downsize back to 1920x1080 which smooths out the image and the edges. As you can imagine this takes a huge toll on the GPU as it has to render many more times the pixels and so is not widely used any more.

    MSAA is an optimization of FSAA where multiple pixels are sampled together rather than each individual pixel in the case of FSAA. MSAA greatly reduces jagged lines and comes at a much lower performance cost than FSAA.

    FXAA is something different as it is a post-processing AA, meaning it applies a smoothing effect after the image is already rendered. Hence this comes at a pretty much zero performance cost as it doesn't require the sampling of any pixels. However the image quality is far below MSAA/FSAA as basically all you're getting is blurring to hide the jaggies.

    If your setup is powerful enough then I'd say MSAA is essential and FXAA is not a replacement. You can also have both turned on as they're not in conflict with each other, but some people dislike FXAA especially in shooting games like BF3 because it makes small objects more blurred (not helpful when you're trying to shoot someone from a distance). In BF3 MSAA is called "Antialiasing Deferred" and FXAA is "Antialiasing Post". I'd say turn up MSAA to the maximum level while still maintaining an acceptable framerate then turn on FXAA if you like the effect (FXAA has minimal performance impact).

    When it comes to settings I believe you can force MSAA or FXAA on/off for individual games in the 3D setting of the Nvidia control panel. Can't tell you exactly where to look or what it's called because I don't have an Nvidia card atm :)
  3. Dawn1113

    Dawn1113 TS Booster Topic Starter Posts: 375   +64

    Thank you very much for taking time to explain this to me, slh28.

    That blurring you mention was what got me to asking whether I had my settings configured all wrong or whether my eyes had just gone from bad to worse. I do lose a good measure of those delicious little textures and details when I have FXAA enabled. I wonder, though, whether the same goes for some of the newer, faster cards. Is GPU speed even a factor in this particular instance?

    I had no idea what FSAA meant before I read your post. But it would indeed seem that an FSAA-based optimization will yield an image of far better quality than one that is smoothed over after it is rendered.

    I have not tried FXAA on BF3 yet, but -- at least for some of the older games I've tested with FXAA -- the blurring can become so bad that certain objects look like watercolor paintings. Objects in the horizon likewise look a bit off, somehow. Maybe those games really aren't meant for it.

    Anyways, again, thanks. Much appreciated.

    PS: That dunk on your avatar looks epic!:)
  4. slh28

    slh28 TechSpot Paladin Posts: 1,925   +170

    GPU speed doesn't have an effect on the image quality, a faster GPU generates more frames but each frame still looks the same.

    Yeah I wouldn't bother with FXAA for older games, you should have the power to run full MSAA judging by your setup.

    TXAA (yet another acronymn for you) was mentioned in the GTX 680 release by Nvidia, apparently it produces 8xMSAA quality images at only 2xMSAA performance cost. Do a quick google images search and you'll see the results look very promising, but it has to be coded into the game engines so might be a while yet before we see it.


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