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The idea of anti-aliasing is to make edges look smooth so it is nicer for human eye to see. But lately with the availability of high-resolution monitor, with high density per inch, which some called as "retina display", is anti-aliasing still required to improve the quality of the image? With such high ppi, human eye is no longer able to distinguish adjacent pixels, so it may look unnecessary to implement AA that will only burden the GPU. Am I understanding correctly?

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  • Most monitors don't have high enough ppi to omit any-aliasing (and those that have are pretty damn expensive). – CodesInChaos Jan 28 '16 at 14:58
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    You are right, rich people owning retina displays are no longer able to distinguish adjacent pixels. – Tulains Córdova Jan 28 '16 at 15:02
  • @CodesInChaos What about mobile phone's display? Nowadays even 5.5-inch phone has 4K resolution. – rcs Jan 28 '16 at 15:03
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    My laptop's resolution is over 1080p but it's still extremely obvious to me when I run a game with the anti-aliasing off. The human eye is just really good at spotting those sharp, unnatural, jagged changes. – Ixrec Jan 28 '16 at 15:08
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    You are correct in that as pixels get smaller, the need for Anti-aliasing decreases. In theory, there's a point where it becomes irrelevant. – DA01 Jan 28 '16 at 19:27
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I'll keep this brief. Yes, anti-aliasing is still very relevant. The reason is that the human eye can see subpixel movements on most displays. You'll often see pixels per degree as the metric used and reference 60 PPD for "retina" displays. The human eye at the center of vision has hyperacuity of small pixel movements that go past 400 PPD. So things like rendered lines that are moving on a high contrast background can appear jarring without AA even though they are very tiny.

Try this demo: http://jsfiddle.net/w5se983j/4/ Walk away from your monitor and you'll see the pixels moving.

That said these AA techniques usually only apply to animation and thin lines. It's very possible that if all you're displaying are images with very little contrast between adjacent pixels that AA will offer very little.

  • Not sure I understand the connection between PPD and 'pixels moving'. Yes, one would see pixels moving on high PPI devices, but not sure that correlated to anti-aliasing, does it? – DA01 Jan 28 '16 at 19:26
  • The point is that anti-aliasing improves the display, so even with a display where usually you don't notice pixels, there are situations where you do, so anti-aliasing still helps. – gnasher729 Jan 28 '16 at 19:33
  • The pixels he is talking about moving are the pixels of the image, not the pixels of the display. Images on computer displays are very often not static. – Simon White Feb 21 '16 at 10:54

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