Talk:Spatial anti-aliasing

message: Anti-aliasing is far more general than discussed here: the general outline is:
* sampling wraps high frequencies into low
* therefore high frequencies should be removed before sampling
* a low-pass filter used for this purpose is called an anti-aliasing filter
* (make mention of reconstruction filters on the reconstruction side of the system)
* applies to digital imaging, digital audio, etc. etc.
-- Anon.
:I dispute this engineer-centric recommendation. "Wrapping high frequencies into low" isn't a very accurate description at best, and simply misleading at worst. Aliasing is based on the pigeonhole principle, and the sinc/signal processing based approaches comes from blind faith in the Fourier transform. Don't take me wrong, I'm a mathematician with some specialization in the Fourier transform, and the Fourier transform is an extremely powerful tool. However, to use a Fourier approach without justification doesn't mean anything. In particular, I oppose "therefore high frequencies should be removed before sampling." It's mostly right, but there's no proof of any kind that's the best thing to do. Loisel 22:32 Jan 23, 2003 (UTC)
::The proof won't fit in the margin. Really, you do need to kill the high frequencies. That's pretty much the whole point of anti-aliasing. AlbertCahalan 00:02, 26 February 2007 (UTC)
replies: text: The article is hugely improved, in any case.  I agree, the sketch above is (cough) non-rigorous handwaving, but even that was better than the really dodgy article which prompted the comments.  Hooray for the Wiki-process, and thanks for your contribution! -- Anon.
I'm a bit confused by the fact it starts by talking about "filters" and frequency-domain stuff but later on just starts averaging multiple samples over each pixel instead.  The latter I always thought of as being antialiasing - your pixel's brightness should be the average of what is inside that pixel not just one point within it.  The sinc filter, while having the nice property of cutting the high-frequency data off at exactly the Nyquist frequency of the display media, can produce odd fringes either side of sharp edges, it's "nonlocal".  —Preceding unsigned comment added by 88.110.208.0 (talk) 05:42, 21 February 2010 (UTC)
replies: text: Simple pixel averaging actually leaves some aliasing in the image. A pure high-frequency sine wave, downsampled in this way, would not vanish, as expected, but might turn into a much lower frequency wave that wasn't present in the original image. Of course, because of the averaging, this artifact wave will have much lesser amplitude than without any filtering. Also, besides the sinc and rectangular-in-space (or pixel-averaging) filters there is a much better compromise, which filters out almost all unwanted frequencies and makes almost unnoticeable fringes near the edges. --87.117.185.177 (talk) 21:53, 24 February 2010 (UTC)
thread_title:  Improving the article 

message: I don't think this passage is pertinent to this article. I am moving it here, it can be restored later. If we were to discuss Gamma correction in here, there's no reason why we wouldn't discuss pixel formats, color theory, interlacing and all these other topics, which do not help at all with anti-aliasing.
(Note that the above assumes that the numerical value of a pixel is proportional to its intensity: for systems where this is not the case, gamma correction must be performed to preserve the linearity of the system, for this approach to hold true).
Loisel 05:31 Jan 25, 2003 (UTC)
Please put it back. Gamma correction problems are the #1 cause of poor anti-aliasing in computer graphics -- doing the A-A computation at the wrong gamma, or displaying the A-A'd image at the wrong gamma, will screw everthing up. <Michael Caine>Not a lot of people know that.</Michael Caine> The Anome
Having worked at SGI and NVidia, I'd say that almost all graphics hardware get the gamma wrong. The only place I've ever seen people complain about it is in film or print, and usually not exactly in those terms because they don't dump the images to the screen, and hence don't have a "gamma" in the final product (although they have to deal with more complicated response curves.) The problem of getting gamma right isn't specific to antialiasing, in fact I would say it affects lighting a whole lot more than antialiasing.
With small pixels, edge antialiasing such as FSAA should only be visible on a small fraction of the pixels (those that are on the edge of a triangle), and for in-triangle AA such as mip-mapping, the adjacent texels are of such a similar color that linear interpolation with or without gamma correction gives almost the same result. Hence, I would argue that being careful with gamma is a whole lot more important for lighting (which affects ALL pixels) than it is with anti-aliasing. And you don't really hear people complaining about how the gamma correction screws up their lighting.
To discuss "frequent problems" with antialiasing, we might need to restructure the article somewhat. Perhaps a section near the end summarizing some related issues. Gamma correction only applies to computer monitors in 8 bits or so per components; perhaps a reference to color theory or some comment about the response curve of the display would be more general. The upcoming graphics hardware should have a flat gamma curve when using floating point framebuffers. Loisel 05:31 Jan 27, 2003 (UTC)
The Anome, do you agree with the placement and wording of the Gamma Correction note now? Loisel 03:25 Jan 28, 2003 (UTC)
It sure does matter. The example images are in fact broken. They get dark near the top, as the checkerboard goes off into the distance. This is wrong. AlbertCahalan 00:02, 26 February 2007 (UTC)
thread_title:  Gamma 

message: Removed "This article certainly needs images!" from Antialiasing article. Created images. Tried to add images. Edit conflict - the new Antialiasing article someone made was merged with this Anti-aliasing article...
What I was going to add:
This image is not antialiased. This image is antialiased. 
Unless someone can think of a good use for them, I guess they can be deleted by whoever can delete uploaded files... Cyp 19:08 Feb 12, 2003 (UTC)
Deleted an image from section Full-scene anti-aliasing as it was unprofessional. C Ronald 10:52, 22 March 2007 (UTC)
thread_title:  About images 

message: ---- What's the difference between figures 1(b) and 1(c)? The article doesn't even hint at the algorithm of figure 1(b), yet the algorithm of figure 1(c) is "considered better". Isidore 21:51, 29 Aug 2004 (UTC)
replies: text: The article does explain it, you just have to read further. The algorithm for 1b  is explained thus: A better approach is, for each pixel, use the average intensity of a rectangular area in the scene corresponding to the surface area of said pixel. This gives a better, but not yet ideal, "anti-aliased" appearance; figure 1-b was generated this way. The alogorithm for 1c is explained a bit further by making a reference to the sinc filter and the aliasing article. Loisel 11:25, 29 Oct 2004 (UTC)
thread_title:  Difference between the anti-aliasing figures 

message: Speaking of gamma correction, it looks very much like the anti-aliased example images are not gamma-corrected... Anders Kaseorg 03:30, 28 Oct 2004 (UTC)
replies: text: You are correct. The checkerboard images should not be dark near the top. AlbertCahalan 00:02, 26 February 2007 (UTC)
replies: text: Same Goes for the mandelbrot spiral images. Applying gamma 2.2 to each would make them look better, but even better, redo the scaling in liear color space. Orbik (talk) 19:29, 22 November 2010 (UTC)
thread_title:  Gamma-corrected anti-aliased images? 

message: At present this article has far more information about mip-mapping than does the mip-mapping article itself.  I believe the text on mip-mapping should be moved to the mip-mapping article and a summary of it should be kept in this article.  What do other people think? MIT Trekkie 04:07, 14 Dec 2004 (UTC)
thread_title:  Mip-mapping article 

message: I might be reading it wrong, but the sentence "It has been observed that to measure a signal of frequency n, you need at least n sample points, and they need to be well-placed." seems to be slightly misleading.  It doesn't specify any sort of time within which the n sample points have to be in. Rspanton 00:03, 24 Dec 2005 (UTC)
thread_title:  "Nyquisty" paragraph 

message: The layout of the pictures really needs to be sorted - at the moment the page looks untidy and some pictures are nowhere near the text that references them.
Romansanders 17:31, 8 April 2006 (UTC)
thread_title: Pictures...

message: I heard theres a ay to turn anti aliasing off in MS paint, can anyone shed some light on that?
I've never seen AA in MSpaint. I just played with it just now, and there is no AA, period (unless I take off my glasses). 206.252.74.48 (talk) 14:33, 3 January 2008 (UTC)
replies: text: If you use the text tool, the text is generally anti-aliased. I don't know of a way of turning this "feature" off, but a workaround is creating the text on a monochrome image (in the attributes window set it to black and white), write your text on that image, then copy and paste from the monochrome image to your colour one. - Rainwarrior (talk) 17:33, 3 January 2008 (UTC)
thread_title:  Turning anti aliasing off? 

message: The 'real time approximations' section and its mipmapping subcomponent don't really fit with the tone of the rest of the article, which is more mathematical/theoretical (as it should be). I was thinking I'd create a new article for AA as used specifically in graphics; mipmapping fits there naturally, as does information about supersampling/multisampling, different sample patterns, coverage masks etc. which again shouldn't really go here, and I haven't seen anywhere else. There's already an article at FSAA but it's pretty scanty. Valarauka 20:49, 17 September 2006 (UTC)
replies: text: I don't think we need to split the article. Every technique applicable to 2D signals (graphics) can be (and is) used for 1D signals. Mip mapping is not just a graphics technique, it's just most commonly a graphics technique. The same goes the other way for the other techniques. The slower filters are used less in real-time graphics (i.e. games), but they're used plenty in imaging software, etc. A decent article on anti aliasing in "computer graphics" is going to overlap with 95% of what goes in this article. A split is not appropriate. - Rainwarrior 21:53, 17 September 2006 (UTC)
replies: text: On second thought, you're probably right. I'm still itchy about the article though... needs improvement. Let's see if I get time. Valarauka 00:48, 18 September 2006 (UTC)
replies: text: A lot of articles on wikipedia need improved organization. This one could probably use some as well. - Rainwarrior 06:04, 18 September 2006 (UTC)

text: Isn't mipmapping for textures? --gatoatigrado 05:52, 4 October 2006 (UTC)

text: Mip-mapping has a few applications to audio signals, and even in non-realtime graphics there are uses. It is rightly an anti-aliasing technique, not an anti-aliasing "avoidance" technique. - Rainwarrior 15:30, 18 October 2006 (UTC)

text: As far as FSAA, it is an application of oversampling, which is an often used anti-aliasing technique. I don't see it being expanded much, so I would support a merge into either this article, or oversampling. - Rainwarrior 15:36, 18 October 2006 (UTC)
thread_title:  New article for Antialiasing (Computer Graphics) ? 

message: I think this article is better than the (already mentioned as small) FSAA (full screen antialiasing) article, and the content should be merged. They are relatively the same thing. I don't think it would hurt this article to include a mention of the methods used in graphics cards, and fsaa could be one of those subheadings. --gatoatigrado 05:48, 4 October 2006 (UTC)
replies: text: Isn't mipmapping for textures? --gatoatigrado 05:52, 4 October 2006 (UTC)

text: Mip-mapping has a few applications to audio signals, and even in non-realtime graphics there are uses. It is rightly an anti-aliasing technique, not an anti-aliasing "avoidance" technique. - Rainwarrior 15:30, 18 October 2006 (UTC)

text: As far as FSAA, it is an application of oversampling, which is an often used anti-aliasing technique. I don't see it being expanded much, so I would support a merge into either this article, or oversampling. - Rainwarrior 15:36, 18 October 2006 (UTC)
thread_title:  merge with fsaa to here 

message: Since eyes can rotate in their sockets, this must have to do with the fact that we are dealing with data sampled on a square lattice and not with a continuous image.
What does that have to do with anything? I think this sentence should go.  User A1 00:14, 15 December 2006 (UTC)
replies: text: Yes, clearly nonsense.  Please do get rid of it. Dicklyon 00:36, 15 December 2006 (UTC)
thread_title:  Whats with this sentence?  

message: The section "First-principles approach to anti-aliasing" includes this statement:
"By the pigeonhole principle, sometimes two different ideal images f(x,y) and g(x,y) will be converted to the same picture on the screen. This cannot be avoided."
While that is undoubtedly true, it is not clear how it is relevant.  The issue is just the opposite, the fact that a single ideal image can be approximated by many alternative reduced images, which creates the challenge of how to select among them.
Steve Wise 04:57, 7 January 2007 (UTC)
replies: text: I think it's completely relevant.  Different real images that have the same sample values are aliases of each other.  That is, this principle is essentially the definition of aliasing.  I'm not sure what you're thinking in your description of "the issue"; I don't see how what you're describing is aliasing. Dicklyon 05:17, 7 January 2007 (UTC)
thread_title:  Is this relevant? 

message: I don't agree that the second image is not related. That is a thumbnail, and you can click to view the larger version. Lugiadoom 08:51, 24 January 2007 (UTC)
replies: text: I didn't say it's unrelated, but it's copyright with no good fair-use rationale, and it doesn't make the point as well as the smaller image does. Dicklyon 16:10, 24 January 2007 (UTC)
thread_title:  Removed image? 

message: The section that was added about criticism might have some good points, but criticisms need to backed up by an attribution to a sourced.  So I took it out.  Put it back when it's ready. Dicklyon 16:10, 24 January 2007 (UTC)
thread_title: Unattributed criticism

message: "The idealized image has infinite detail, and is represented by a function f(x,y) where x and y are real numbers defining coordinates."
Infinite or just enough to match the resolution of the human eye? Maybe some elaboration could follow this sentence. --RITZ 04:03, 7 March 2007 (UTC)
replies: text: For the purposes of this article, infinite. If you want to know how much detail there actually is, you have to learn quantum physics. For all intents and purposes, the detail is infinite. The human eye has nothing to do with the idealized image. Loisel 00:40, 8 March 2007 (UTC)
thread_title:  Infinite Detail 

message: "Game consoles and type setting on screen of personal computers employ antialiasing in realtime. Windows Picture and Fax Viewer, Microsoft Powerpoint, Adobe Acrobat Reader, Ghostview, the aqua and aero window managers employ it full screen, while the Gimp and OpenOffice.org Impress are not able to."
That sounds really irrelevant to me. Also like an attempt to discredit and belittle the quality of OpenSource Software, due the wording and the selection of commercial software on one side, the GIMP and OpenOffice on the other side. 217.235.93.78 19:18, 15 July 2007 (UTC)
replies: text: Well, I fact tagged it, and then Rainwarrior took it out; so if it comes backs, it will certainly have to be fixed to be in agreement with sources it cites.  Problem solved. Dicklyon 21:50, 15 July 2007 (UTC)
replies: text: I didn't see the point of any of that information. A comprehensive list of programs that do or do not use anti-aliasing would be gigantic, and of no practical use. Also, "game consoles" is far too unspecific to be true as a general statement; it might be true for the new generation (e.g. Microsoft put anti-aliasing on the XBox 360's Technical Requirements Checklist), but definitely wasn't in the not too distant past (the difference on your average television was probably too negligible to be important). - Rainwarrior 04:17, 16 July 2007 (UTC)
replies: text: The potential value would be in knowing what platforms or APIs support what kind of anti-aliasing.  If there's a source for such info, the list shouldn't so open-ended as a list of apps. Dicklyon 04:42, 16 July 2007 (UTC)

text: Someone may be thinking about Microsoft's Cleartype technology, which is an interesting form of antialiasing, but a correct comment should be included. DonPMitchell (talk) 22:30, 5 July 2008 (UTC)
thread_title: Uh, what?

message: Pictures are in some strange non-linear color space, instead of sRGB. 83.4.200.31 (talk) 20:34, 4 January 2010 (UTC)
thread_title:  Wrong pictures 

message: In the FSAA section "jaggies" are considered to be the only aliasing effect which is NOT correct. In fact there are effects like "moire" or loosing edges, curves(some high frequency geometry) altogether rather then having "jagged" edges. Unfortunately people have a false perception of "aliasing = jagged edges" because of this false treatment of the subject. Please correct it.  —Preceding unsigned comment added by 24.61.87.72 (talk) 21:10, 29 June 2010 (UTC)
replies: text: While there are a variety of aliasing effects, computer generated graphics anti aliasing (such as FSAA) ONLY deals with juggies, and not those other effects. (keep in mind, that as a fully artificial image, it does not actually HAVE many of the artifacts found in photography/video recording. While at the same time, juggies are exclusive to computer generated graphics. --Taltamir (talk) 22:07, 10 January 2011 (UTC)
thread_title:  Jaggies ??? 

message: How about Morphological anti-aliasing which is coming into effect as the new Radeon 6000 series releases? Some of it is discussed in this article: http://www.tomshardware.com/reviews/radeon-hd-6870-radeon-hd-6850-barts,2776-4.html IOA94 (talk) 20:32, 1 November 2010 (UTC)
replies: text: Is Morphological anti-aliasing abreviated to MLAA? Because MLAA redirects to this article but is nowhere mentioned. --145.120.12.196 (talk) 20:06, 4 April 2012 (UTC)
replies: text: MLAA is indeed the abbreviation of Morphological anti-aliasing. I do hope that the article is expanded to mention it. Since there are already articles for FXAA and [[MSAA]|, it might even make sense to create a dedicated article for MLAA. Norrk (talk) 12:46, 25 November 2012 (UTC)
thread_title:  Morphological Anti Aliasing 

message: Is the line 
"The ear is predominantly sensitive to lower frequencies. And so, in signal processing, we choose to eliminate all high frequencies from the signal, keeping only the frequencies that are low enough to be sampled correctly by our sample rate."
strictly necessary and in context?
Evn2-NJITWILL (talk) 20:22, 23 November 2010 (UTC)
replies: text: The ear was pretty irrelevant in that discussion, but a lot more was wrong, too.  In this edit, I tried to clean it up and remove the nonsense.  The section assumed that the sampling theorem had a converse, and that an ideally sharp filter would be best for image anti-aliasing; neither is true.  Dicklyon (talk) 04:56, 28 November 2010 (UTC)
thread_title:  Signal processing in the ear 

message: Is this article supposed to be only about anti-aliasing in graphical display systems?  Anti-alias (low pass) spatial filters are a part of many digital cameras, needed to prevent aliasing due to the spatial sampling of the image sensor.  There is a little in the anti-aliasing filter page, but not so much. Given the title of this page, it should include optical (spatial) low-pass anti-alias filters, too. Gah4 (talk) 21:20, 17 August 2017 (UTC)
thread_title:  Digital photography 

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