A Guide to Anti-Aliasing
Written by alt639 on 22 July 2013 at 19:37

It doesn't take a genius to tell you that games can look very different on different PC's, depending on the hardware and game settings.

One of the settings with the most performance impact is Anti-Aliasing; but what exactly is it, and how does it work? Alt639 is here to educate us, so read on to become an expert...

A Guide to Anti-Aliasing

Anti-aliasing is a process that corrects jagged edges appearing on geometry in games. There are two different types of anti-aliasing, which work in different ways: deferred and shader algorithms. Deferred variants work by rendering the frames multiple times at a higher resolution, then downsampling the image to be displayed. Shader algorithms work by analyzing the frames and applying a blur filter over edges. Generally speaking, deferred techniques are graphically superior, while being more hardware intensive. Now that we have covered the basics, let's take an in-depth look at all the different techniques. (Mouse over the images to see their titles)

Deferred Anti-aliasing 

• Full scene anti-aliasing (FSAA): Also commonly known as super sample anti-aliasing, this technique simply renders the frames at a much higher resolution, then downsamples them to the appropriate resolution. What you get is a much softer and realistic scene, but, depending on your hardware, also comes with a steep performance hit. By virtue, using FSAA is the "best" choice for eliminating jagged edges, because of the way it operates. It also anti-aliases the alpha, or transparent, channels of textures. This was the first type of anti-aliasing used, but is now only viable in modern games for those with flagship GPUs, like the Radeon HD 7950/7970 or GTX 670/680.

• Multi sample anti-aliasing (MSAA): A derivation of FSAA, this technique is optimized to increase performance by only super sampling the depth and outline values associated with geometry. So, edges are super sampled, but nothing else is, which detracts from the softened detail that FSAA confers. MSAA also does not anti-alias alpha channels by itself, so it must be used with a form of transparency multi sampling if one wishes to anti-alias transparent textures. For Nvidia cards, this would be in the form of sparse grid super sample anti-aliasing, SGSSAA, which specifically targets alpha textures.

• Adaptive multi sample anti-aliasing (AMSAA): AMD graphics cards benefit from this technique, which combines traditional MSAA and transparency multi sampling. It effectively combines the two without a particularly noticeable effect on performance. The downside to this technique is that, occasionally, visual artifacts occur. DirectX 11 games, like Far Cry 3 and Battlefield 3, don't seem to suffer from this issue, but some DirectX 9 titles, most notably Skyrim, do encounter strange errors.

• Custom filter anti-aliasing (CFAA): Not exactly a form of anti-aliasing, CFAA is another AMD exclusive technology that changes the way that MSAA is applied to the scene. In earlier releases of the Catalyst drivers, users could select from four different filters: box, narrow tent, wide tent, and edge detect. As of the 13.6 Beta, only standard (box) and edge detect remain. What these filters do is change the radius of sampling, which basically equates to more samples. Box is no increase, narrow tent is a small increase, and wide tent is a larger increase. The edge detect filter is a notable exception though; it applies an algorithm that helps to, well, detect more edges, along with a sampling increase.

That's about it for deferred techniques. Keep in mind that performance may wildly vary between games using these types of anti-aliasing. Far Cry 3 becomes unplayable with more than 4x MSAA, while Left 4 Dead 2 remains above 60 FPS with 12x edge detect SSAA. Obviously the depth of the scene will have a large effect on these results.

Shader Algorithms 

• Fast approximate anti-aliasing (FXAA): Perhaps the most well known shader algorithm, FXAA is an Nvidia technology that works in an extremely simple fashion. The algorithm searches for all edges in the image, then blurs them to anti-alias the edges. It also works on alpha textures, as do all the shader techniques, and where MSAA causes a sharp decline in performance, FXAA has almost no noticeable impact. However, texture detail is not as sharp when using FXAA because of the way it operates. It's great for those who don't mind sacrificing a bit of image quality.

• Temporal anti-aliasing (TXAA): TXAA actually combines MSAA with a temporal filter. What this means is that you can achieve quality above 8x MSAA with the performance impact of 4x MSAA. It also doesn't blur the scene as much as FXAA does. It is another Nvidia exclusive, and carries the largest performance hit of all the shader techniques. Interestingly enough, temporal anti-aliasing was first used by AMD with the release of the X800 graphics card, but was abandoned because it became problematic with newer games.

• Morphological anti-aliasing (MLAA): AMD's exclusive MLAA works much the same as the other techniques, by finding edges and adding post-process blur. However, AMD has tuned it to produce results similar to SSAA with a performance impact close to 2x MSAA. It also doesn't blur texture detail as much as FXAA does.

• Sub-pixel morphological anti-aliasing (SMAA): SMAA was independently developed as an even cleaner version of MLAA. It works in a similar fashion, but without any noticeable blurring or performance decrease. The injectSMAA tool has become a favorite of many gamers for its versatility. Pure SMAA is a single sample, whereas in Crysis 3, it combines several different techniques under the same name. 2x SMAA is SMAA with transparency super sampling, and 4x SMAA is 2x SMAA along with 2x MSAA.

• Sub-pixel reconstruction anti-aliasing (SRAA): Nvidia is currently working on a new form of anti-aliasing that works similarly to MLAA, but approaches quality comparable to 16x SSAA! It also renders faster than any other form of anti-aliasing, meaning that it will deliver the best possible image quality for the least performance cost when it is finalized. If you'd like to read more about it, Nvidia has a PDF on the subject Here

I'd also like to quickly address a glaring misconception. Many people like to believe that anti-aliasing has no benefit at 1920x1080 or above, however this is not true. As you can see in the following image, without anti-aliasing there are a significant amount of jagged edges even on my 22" 1080P monitor. As seen in the images under each heading, the jagged edges are almost completely removed with the addition of anti-aliasing. Until such a time that we see WQHD or 4K resolutions in a smaller form factor, anti-aliasing will have a very noticeable effect on image quality.

So how educational did you find it? Do you guys now feel more comfortable chatting about anti-aliasing? Tell us below!

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deadwarrior63
09:33 Aug-13-2013
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I still cannot notice a difference between 8x AA and No AA. Even the sample picture showed almost no differences to me. I might just be blind.

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Tero
20:27 Aug-13-2013

Look at the edges ;)

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deadwarrior63
01:35 Aug-14-2013
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Now I see it.. had to zoom in a little but I've seen it now. The only thing is though that AA goes unnoticed in BF online gameplay as you're too busy trying to not get shot to take in the scenery :P

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arieljersey1
05:00 Aug-03-2013
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I just put all my games to ultra. I don't really know this things i just want to play! :D

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XxSoultheKeeperXx
05:22 Aug-03-2013

That is one hell of a monster, that board has the most FLOPs per dollar in the world

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Interrogator
05:35 Aug-03-2013
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I wish I had that money.
I cri evertiem ;-;

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Tero
09:19 Aug-12-2013

Same here (other than AA mostly) :D
If the game lags, I upgrade my GPU :P

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Interrogator
03:06 Jul-27-2013
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Hmm FXAA does makes everything blurry and destroy your framerates, I activated it on The WItcher 2 and it looked worse and my game was all slow.

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tzzsmk
19:17 Jul-27-2013

generally, fxaa doesn't decrease fps noticeably;
didn't you mean UberSampling in TW2 ?

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Interrogator
21:13 Jul-28-2013
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yep

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XxSoultheKeeperXx
22:09 Aug-02-2013

I'm not surprised lol Ubersampling is FSAA (SSAA)

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Interrogator
22:12 Aug-02-2013
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well, I'll be damned.

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absolitude
12:49 Jul-26-2013
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yes, i prefer going with aa, but in some games, it's just so fps dropping

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absolitude
17:52 Jul-29-2013
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im bookmarking this for sure

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NVIDIAGeForceGTX
00:58 Jul-25-2013
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I don't notice anti-aliasing only when the game runs above sixty frames per second, if it's fifty nine frames per second, then I can notice it. I am very sensitive to frame rate drops.

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austinach
00:19 Jul-25-2013
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I dont see any difference in AA on or off. so i always keep it off for best FPS unless i can turn AA on with out a game going under 45 fps :D

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Tero
05:47 Jul-25-2013

24" with that resolution… o.0

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NVIDIAGeForceGTX
12:32 Jul-25-2013

yea i used 18.5" and i saw the difference and i can't understand how he can't see the difference at 24"!

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austinach
23:05 Jul-26-2013
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yeah, it sucks, im getting an asus 23" in august :)

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TheGHOSTyA
20:05 Aug-02-2013
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DAFUQ

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balonas29
17:31 Jul-23-2013
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I just want my game look more realistic,I do't care about the edges of the weapons,vehicles or other stuff.
BTW…if I get an Asus nVidia GeForce GTX 650 1 GB,waht AA should I apply?

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Interrogator
17:42 Jul-23-2013
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probably no AA.
get the Ti BOOST version of it.

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thasan1
17:43 Jul-23-2013
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for that res, maybe 4X AA, or whatever that game supports at max.

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balonas29
18:02 Jul-23-2013
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Neah…this resolution will be trashed,and I'll get a 1366x768 18.5 inch LG LED screen!
Anyway,The Ti BOOST version is a bit more expensive…so I'll leave the AA for the high price graphics card!
Thank you for the advice!

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kristijonasz
15:22 Jul-23-2013
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Articles like this should get a like button so we could express our joy. Thanks!

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thasan1
15:05 Jul-23-2013
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for some reason i dont see any difference between the AA samples O.O oh and what is a shader algorithm?

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alt639
16:07 Jul-23-2013
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Here is a better comparison. Note especially the weapon, edges of the vehicles, the windows and fences in the background.

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ronron14
14:13 Jul-23-2013
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Nice Article.. Really helps.. btw.. Can anyone direct me to the articles of GPU Technology..?

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tzzsmk
14:20 Jul-23-2013

this one is definitely worth checking :Đ

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ronron14
14:30 Jul-23-2013
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Oh nice.. Many Thanks.. But I still want the Article about GPU Technology.. It saw posted months ago already..

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alt639
16:05 Jul-23-2013
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Can you be specific about what you'd like to see?

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XxSoultheKeeperXx
22:19 Jul-23-2013

I think he means pips 3 part article about GFX (great bit that is :D)

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