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Comment by calibas | Hacker News Reader

If you want a good example of what happens when you treat pixels like they're just little squares, disable font smoothing. Anti-aliasing, fonts that look good, and smooth animation are all dependent upon subpixel rending.

https://en.wikipedia.org/wiki/Subpixel_rendering

Edit: For the record, I'm on Win 10 with a 1440p monitor and disabling font smoothing makes a very noticeable difference.

People are acting like this is some issue that no longer exists, and you don't have to be concerned with subpixel rendering anymore. That's not true, and highlights a bias that's very prevalent here on HN. Just because I have a fancy retina display doesn't mean the average user does. If you pretend like subpixel rendering is no longer a concern, you can run into situations where fonts look great on your end, but an ugly jagged mess for your average user.

And you can tell who the Apple users are because they believe all this went away years ago.

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This might have been a good example fifteen years ago. These days with high-DPI displays you can't perceive a difference between font smoothing being turned on and off. On macOS for example font smoothing adds some faux bold to the fonts, and it's long been recommended to turn it off. See for example the influential article https://tonsky.me/blog/monitors/ which explains that font smoothing used to do subpixel antialiasing, but the whole feature was removed in 2018. It also explains that this checkbox doesn't even control regular grayscale antialiasing, and I'm guessing it's because downscaling a rendered @2x framebuffer down to the physical resolution inherently introduces antialiasing.

Maybe true for Mac users, but the average Win 10 desktop is still using a 1080p monitor.

The users may have 1080p monitors, but even Windows does not do subpixel antialiasing in its new apps (UWP/WinUI) anymore. On Linux, GTK4 does not do subpixel antialiasing anymore.

The reason is mostly that it is too hard to make it work under transformations and compositing, while higher resolution screens are a better solution for anyone who cares enough.

> even Windows does not do subpixel antialiasing in its new apps (UWP/WinUI) anymore

This is a little misleading, as the new versions of Edge and Windows Terminal do use subpixel antialiasing.

What Microsoft did was remove the feature on a system level, and leave implementation up to individual apps.

Is this why font rendering on my Win11 laptop looks like shit on my 1440p external monitor?

Laptop screen is 4k with 200% scaling.

Seriously the font rendering in certain areas (i.e. windows notification panel) is actually dogshit. If I turn off the 200% scaling on the laptop screen then reboot it looks correct again.

You’re conflating different topics. LCD subpixel rendering and font smoothing is often implemented by treating the subpixels as little rectangles, which is the same mistake as treating pixels as squares.

Anti-aliasing can be and is done on squares routinely. It’s called ‘greyscale antialiasing’ to differentiate from LCD subpixel antialiasing, but the name is confusing since it works and is most often used on colors.

The problem Alvy-Ray is talking about is far more subtle. You can do anti-aliasing with little squares, but the result isn’t 100% correct and is not the best result possible no matter how many samples you take. What he’s really referring to is what signal processing people call a box filter, versus something better like a sinc or Gaussian or Mitchell filter.

Regarding your edit, on a high DPI display there’s very little practical difference bewteen LCD subpixel antialiasing and ‘greyscale’ (color) antialiasing. You don’t need LCD subpixels to get effective antialiasing, and you can get mostly effective antialiasing with square shaped pixels.

We're going off on tangents here, I only brought this up to reinforce the idea that a pixel is not a little square.

And I guess I should have explicitly stated that I'm not talking about high-DPI displays, subpixel rendering obviously doesn't do much good there!

My point is simply this, if you don't treat pixel like discrete little boxes that display a single color, you can use subpixels to effectively increase the resolution on low-DPI monitors. Yes, you can use greyscale antialiasing instead, you will even get better performance, but the visual quality will suffer on your standard desktop PC monitor.

Yes, LCD subpixel rendering is a tangent, it’s not relevant to Alvy-Ray’s point. And again, LCD subpixel rendering is treating pixels as little squares; cutting a square pixel into 3 rectangles doesn’t change anything with respect to what Alvy Ray was talking about. So-called grayscale antialiasing on low-DPI displays is nearly as good as LCD subpixel, the quality differences are pretty minor. (Plus it’s a tradeoff and you get the downside of chromatic aberration.) I think you’re suggesting visual quality suffers when you don’t do any antialiasing at all, which is true, but that’s not what Alvy-Ray was talking about. Treating a pixel like a square does not imply lack of antialiasing.

I should have been more clear, I'm not responding to Alvy-Ray's article, I was simply adding to the idea that a pixel is not a little square.

If you don't treat a logical pixel like a discrete little square, you can take advantage of subpixel geometry to effectively increase the resolution. It's not the same as antialiasing, even though it can be used for antialiasing.

Arguably, instead of treating pixels as squares, you're treating them as three times as many rectangles, but that should still contradict the mental model of pixels as little squares.

> that should still contradict the mental model of pixels as little squares.

No, it doesn’t. You seem to be missing this point. Using subpixel rectangles does not in any way correct the misconception, it perpetuates it.

I don't think that's true anymore. Modern high-resolution displays have pixels small enough that they don't really benefit from sub-pixel rendering, and logical pixels have become decoupled from physical pixels to the point of making sub-pixel rendering a lot more difficult.

It's still true for everyone who doesn't have a high DPI monitor. We're talking about a feature that doubles the price of the display for little practical value. It's not universal, and won't be for a long time.

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