Alternative AA methods and their comparison with traditional MSAA*

[AlNom]

Well, it's better than the FXAA stuff in Skyrim, plus it's on 360. :s

 

[Andrew Lauritzen]

Oh I'm not being negative... I'm actually curious. The only pessimistic overtone I was conveying is just more of people concluding stuff ("crawling/sub pixel problems are not as pronounced as in other types of post process AA techniques") without actually comparing them on the same assets/game. The two are not independent.

 

[MJP]

I haven't seen the game in person, but based on the description it sounds like they used an existing post process AA solution and tweaked it to only be applied on geometry edges (probably using depth, normal, or even material discontinuities).

 

[AlNom]

Wondered if maybe it was Jimenez MLAA or something. *shrug*

Anyways, the Edge Detection does look quite a bit better than anything else I've seen so far on the console, so maybe they use depth afterall. (wonder if they had to access/use depth anyway for doing the 3D mode so the cost was already considered?)

Oh I'm not being negative... I'm actually curious. The only pessimistic overtone I was conveying is just more of people concluding stuff ("crawling/sub pixel problems are not as pronounced as in other types of post process AA techniques") without actually comparing them on the same assets/game. The two are not independent.

Oh, I have no clue about the sub-pixel crawling thing. I just know about the filtering.

 

[Ruskie]

I don't know about crawling either, thats what DF wrote. I have game on my 360 and it does look very smooth. Beta on PS3 on the other hand was actually jaggier and blurrier, they probably tweaked it.

http://i.imgur.com/ziZWp.jpg

 

[IrYoKu]

Skyrim has MSAA + FXAA (to solve transparency antialiasing), but applying post AA filter on top of standard MSAA resolve is just wrong. The AA filter should use the subsamples to improve the edge gradient calculation, not just do two blends on top of each other. If I understand properly SMAA should address this problem?

Combining temporal "subsample" data with post process AA filter is a good idea. But just doing both on top of each other (brute force way) doesn't of course do much good. The algorithm needs to be more intelligent than that. SMAA seems to be the first solution towards that path.

We tried to leverage the subsample information in various ways.

The first thing we tried is applying MLAA on top of a resolved image. Unfortunately, this didn't work. Edge detection fails as the edges have much less contrast after the resolve; furthermore, even if you run the edge detection pass on top of the original unresolved data, the coverage areas used for blending will not produce the correct values (as the pixels are already blended by the 2x resolve). We tried to bias this in various ways, but we came to the conclusion that it's impossible to do it in a general way. Here you have what happens if you do MLAA after resolving:

http://www.flickr.com/photos/70160915@N03/6373855775/

Then, we tried to apply MLAA before resolving. It worked better, but it was still performing worse than MSAA for the same sample count, with regards to subpixel features (see MLAA + 4x):

http://www.flickr.com/photos/70160915@N03/6373890101/

This is because of two main reasons. The first one is that MLAA tends to round everything at subpixel level. This means that MSAA or SSAA won't be able to correctly resolve into the proper values. The second reason is that MLAA assumes the revectorization to be centered in the pixel (MLAA or any other postprocessing AA). However, when supersampling or multisampling MLAA, this revectorization must be moved to the center of the sampling pattern:

http://www.flickr.com/photos/70160915@N03/6373856415/

The problem is that if we don't do this, areas will be over/understimated, causing objects to glow. Furthermore, applying MLAA with MSAA will never converge to MSAA despite using really high sample counts.

Other option we tried is running MLAA at subpixel level; however, postprocessing antialiasing does not work well with rotated grid patterns, which rules out any MSAA approach.

On an off note, I'd always wondered if anyone's tried some form of mlaa on shadow maps. Maybe not too useful as MSAA'd shadow maps are a lot cheaper than the full color sample and etc. that you need for your frame, but it just sounds like an interesting experiment. I bring it up mainly because of Skyrim's horrible aliased shadows, not even changing them to x4096 myself has truly solved the problem.

It could be used for rendering antialiased hard shadows if used in tandem with VSM or ESM (as regular shadow mapping cannot be prefiltered). For soft shadow mapping I think it would be less useful because the blurring gets rid of aliasing anyway.

It's true that motion blur helps in these cases, but it's not a perfect solution. Furthermore there are still valid small motion scenarios that break under reprojection caching like high frequency foreground geometry (blinds, foliage, etc) that occludes very different fragments each frame even if the camera/objects are moving relatively slowly.

Agreed; actually, it's easy to find these scenarios by playing with our demo. We think that mixing MLAA, MSAA and temporal SSAA into a single technique is a good approach because it offers fallbacks in these kind of failure scenarios.

Yes, but with a certain console, you cannot directly use rendertarget as a texture. You have to resolve the contents first to main memory. 720p full screen resolves are not cheap. A few of them, and you already have 1 ms spent.

This is actually a problem of our MLAA approach on that console. Half of the time is spent on resolves. We've various ideas to improve things on consoles, we hope to get a devkit soon to try them!

With FXAA you of course have to do a separate edge detect pass, if you want to use the stencil culling. But many engines have multiple existing full screen passes (tiled deferred lighting for example) that can easily be modified to do the edge detection in addition to their usual work. For example if you integrate the edge detection to the full screen (tiled) lighting pass, you already have the depth sampled (for position calculation), and only need to sample the neighbors' depth (that are fortunately in texture cache). So the edge detect become really inexpensive.

We like doing the edge detection step on the motion blur pass, because this way you can skip pixels that will receive a lot of motion blur. And also because the neighbors will probably be in the texture cache (as you mentioned), it will add little overhead.

Regarding Assasins Creed Revelations AA, it looks really nice indeed!

 

[Andrew Lauritzen]

Lots of good information! Thanks for taking the time to explain that all and show pictures. I think I understand your technique, and more importantly the reasoning by which you arrived at it, better now I agree with your conclusion as well... we need to use a combination of several AA techniques to get an efficient, high-quality solution.

 

[Man from Atlantis]

I'm glad to present you Inject SMAA by mrhaandi

This is only SMAAx1.. i hope he will enhance it further..

Install
If the game uses DirectX 9, put all files from the d3d9 directory into the directory containing the game executable.
If the game uses DirectX 10/11, put all files from the d3d10 directory into the directory containing the game executable.


Uninstall
Remove the files.


Notes
You may need to run your applications as administrator (required to write the logfile).
Do not use this tool while playing on anti cheat enabled servers (may be detected as a cheating measure)!
Do not mix d3d9 and d3d10 the files.
Install the latest DirectX runtime.
A "log.log" file is created to log behaviour/ bugs. Look inside to get additional information.
If the "log.log" file is not created then you use the wrong "*.dll" or you put it into the wrong directory.
Try to put the files into different directories before saying it doesn't work.


Keys
PAUSE : Enable/Disable SMAA
PRINT SCREEN : Screenshot

NoAA

Inject FXAA

Inject SMAA

 

[homerdog]

FXAA looks better? There's some heavy jpg compression going on there so it's hard to tell. I hope he enables the higher quality modes at some point.

 

[Ethatron]

FXAA looks better? There's some heavy jpg compression going on there so it's hard to tell. I hope he enables the higher quality modes at some point.

Actually it doesn't, look at the thin branches of the tree, FXAA smears it all over.

 

[homerdog]

It's not really worth arguing over. FXAA looks better IMO, but that isn't going to take the discussion very far.

 

[snarfbot]

looks pretty darn good to me, heres a cap of dead space with it.

smaa

fxaa

honestly i cant tell the difference when im playing, but the smaa does look a bit better in screen caps.

thanks atlantis.

 

[doob]

I'd prefer it over the other 2 fxaa injectors that were released/repacked with the sharp(and other) filter(s) *edit* if it had them as well*edit*. As i personally prefer to keep the post-aa blur(and bloom) toned down(but with high precision values, focusing mostly on contrast) while giving priority to crisper/sharp textures, it can do wonders in some games as small details (and/or patterns) become more vivid and less muddy/smudged.

Untill then i'll just keep an eye on smaa as a potencial replacement.

 

[Man from Atlantis]

Skyrim_NoAA Skyrim_FXAA Skyrim_SMAA
Skyrim2_NoAA Skyrim2_FXAA Skyrim2_SMAA
Battlefield3_NoAA Battlefield3_FXAA Battlefield3_SMAA
MassEffect2_NoAA MassEffect2_FXAA MassEffect2_SMAA
DragonAge2_NoAA DragonAge2_FXAA DragonAge2_SMAA
TheWitcher2_NoAA TheWitcher2_FXAA TheWitcher2_SMAA


SMAA 1x a bit slower in my tests but clearly better looking than FXAA.. plus SMAA doesnt add extra blur at least it's not noticable as FXAA..

download .BMP files

 

[fellix]

SMAA definitely handles GUI elements better.

 

[homerdog]

Skyrim_NoAA Skyrim_FXAA Skyrim_SMAA
Skyrim2_NoAA Skyrim2_FXAA Skyrim2_SMAA
Battlefield3_NoAA Battlefield3_FXAA Battlefield3_SMAA
MassEffect2_NoAA MassEffect2_FXAA MassEffect2_SMAA
DragonAge2_NoAA DragonAge2_FXAA DragonAge2_SMAA
TheWitcher2_NoAA TheWitcher2_FXAA TheWitcher2_SMAA


SMAA 1x a bit slower in my tests but clearly better looking than FXAA.. plus SMAA doesnt add extra blur at least it's not noticable as FXAA..

download .BMP files

I can't tell much difference between FXAA and SMAA TBH. I'll have to study these screenies some more. :smile:

BTW Skyrim supports a very technologically advanced AA mode called MSAA that looks better than FXAA and SMAA and is basically free on modern GPUs. I don't know how they managed to pull it off, must be geniuses or something.

 

[Deadly Towers]

SMAA gives smother diagonal edges; it's not as crawly in motion.

Skyrim has some effects that break MSAA, so the multisample version of SMAA would be a good approach there.

 

[KKRT]

BTW Skyrim supports a very technologically advanced AA mode called MSAA that looks better than FXAA and SMAA and is basically free on modern GPUs. I don't know how they managed to pull it off, must be geniuses or something.

If only MSAA was good enough for Skyrim ;\ and i wish it was free ;p I'll need to test, if it gives me better results with 1.5x1.5 OGSSAA in Skyrim in comparison to 4xMSAA.

 

[Man from Atlantis]

a little more blur could help especially in Mass Effect 2 and Dragon Age 2.. looks better with FXAA..

 

[homerdog]

If only MSAA was good enough for Skyrim ;\ and i wish it was free ;p I'll need to test, if it gives me better results with 1.5x1.5 OGSSAA in Skyrim in comparison to 4xMSAA.

Considering even my GTX260 can hold 60fps with 4xMSAA I'd call it free. You'll be CPU limited in this game unless you have a very weak GPU or are doing some crazy supersampling (which I guess you are..).

I use 4xMSAA + FXAA and the IQ is very nice. There are no jaggies to be found anywhere; the only aliasing I see is related to specular highlights and transparencies.