Comment by TheLoneWolfling | Hacker News Reader

Comment by TheLoneWolfling | Hacker News Reader

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TheLoneWolfling

You're forgetting movement. Which is not an issue with printers, but is an issue with displays. Such as when scrolling and such. You can detect the difference between moving at 5 inches/sec and, say, 7.5 inches/sec quite easily.

With no subpixel rendering, assuming a framerate of 60fps, you can move only at the following speeds: 5 inches per second (1 pixel / frame), 10 inches per second (2 pixels per frame), 15 inches per second (3 pixels per frame)...

If you're running at 60 FPS and don't mind judder above 30FPS (hideous, but some people apparently don't mind it. I am not one of those people. On a related note: for some reason PM occasionally tears webpages when scrolling, and it drives me crazy), things are a little better, but not much. 2.5 inches / second (1 pixel / 2 frames), 3.75 inches / second (1 pixel then 2 pixels, alternating), 5 inches / second (1 pixel / frame), 6.25 inches / second (2 pixels then 3 pixels, alternating)...

You cannot maintain a scroll speed slower than 5 inches per second (approximately: 300dpi @ 60fps. If you compromise for 30fps, that's 2.5 inches per second instead) without dropping your effective framerate without subpixel rendering. This is an issue all over the place.

As such, yes, subpixel rendering is still required even with retina displays.

Yes, you need the ability to draw content at fractional pixel offsets to get smooth motion. That's different than the "subpixel rendering" the original post was talking about, though, which is a way to draw sharper shapes (usually text) by addressing the red, green and blue "subpixels" individually: https://en.wikipedia.org/wiki/Subpixel_rendering

Except that they are functionally identical. In order to draw at subpixel offsets you need subpixel rendering (or rather: if you have drawing text at subpixel offsets without proper subpixel rendering you get really bad artifacts)

Your claim that you get really bad artifacts on a retina display when you draw lines properly is also needs citation. I don't know if the retina display has enough pixels to meet the claims either, but it seems you're confusing anti-aliasing with subpixel rendering.

https://en.wikipedia.org/wiki/Spatial_anti-aliasing#Examples

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

It is possible to show, however, that if a scene has a band-limited detail property and the join response of your visual system, your eyes' point spread function and the pixel geometry resembles a Nyquist pulse, then indeed there is a density (which would be equal to the density where 1 pixel is covered by 1 sampling element in the retina) which is sufficient for perfect reconstruction of the image, even if it is moving.

> It is possible to show, however,

Yes. However, the retina display is not there yet.

All you need is regular antialiasing, not subpixel antialiasing. To be precise about what I mean: drawing a black line on a white background with regular antialiasing will produce only black, white and gray pixels. Subpixel antialiasing will produce colored pixels. What I'm saying is that you don't need the colored pixels to produce smooth motion.

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