[gwillen]

This is dumb. The fact that one pixel subtends a particular visual angle does not imply that N pixels subtend N times that angle. It should be very plain to anybody implementing or using a rendering engine that pixels are intended to be linearly additive. This implies that N pixels will subtend less than N times the angle one pixel subtends. On a flat screen, this is normal and expected, because a pixel further from the eye will subtend less angle than a pixel closer to the eye.

[modeless]

The fact that this measurement is an approximation (and a very good one in fact) doesn't make it "dumb". In fact, it's flat displays that are "dumb". An optimal display would be curved so that each pixel subtends a roughly equal visual angle, and it's only the fact that most displays subtend a relatively small visual angle that allows us to approximate this with flat displays.

[nwatson]

A curved display (let's say, spherical) centered approximately at the "primary" observer's eyeballs whose pixel elements all subtend equal solid angles would (a) lead to weird unintuitive and hard-to-program-for locations in their most natural expressions the further you wandered from the center-horizontal or center-vertical row/column of pixels; (b) make it very hard to those whose eyeballs aren't smack-dab in the center of the sphere to make an intuitive mapping from their distorted view of the screen to something that makes sense.

A flat screen is best for general use.

[modeless]

I agree that a spherical display the size of a monitor or TV would be unweildy; however a head-mounted display with a large field of view would work best if it was curved.

[jonah]

Well, if you want to program for a spherical display there's the 30 foot diameter AlloSphere: http://www.allosphere.ucsb.edu/

[voyou]

You're right, and the article linked here is wrong. The CSS spec doesn't say that px is an angular measurement, and the formula given that is supposed to convert between px and radians has no basis in the spec. The spec specifically defines px as a length; angular measurements only become relevant in calculating the reference pixel, which is a length used to define the size of 1px in circumstances where physical pixels are significantly different in size from the physical pixels of a computer monitor.

[kijin]

OK, so based on the following spec:

> It is recommended that the reference pixel be the visual angle of one pixel on a device with a pixel density of 96dpi and a distance from the reader of an arm's length. For a nominal arm's length of 28 inches...

It would seem that the reference pixel is simply 1/2688 of the typical distance between your eyes and the device. If a device is meant to be used at half the "arm's length" distance (14 in), the reference pixel on that device would be only half as large. If a device is meant to be used at 3x times the distance (84 in), the reference pixel would be 3x larger. Much easier than angular diameters.

[crazygringo]

That's actually a very good point, don't know why you're being downvoted.

[gwillen]

I find it interesting that I was downvoted to the negatives, then you posted this reply, and then I got upvoted to the top. I wonder what the causation is there.

I suspect I know why I was downvoted; I used unnecessary emotive language ("dumb") and didn't explain my point clearly. Most of the rest of the commenters were focused on one part of the article's point, which is very relevant -- the idea that a pixel is no longer a pixel, but a particular fraction of an inch of screen space. I was complaining about a different part, which is the article author's claim that the function mapping real pixels to CSS pixels is nonlinear (which I think is just a misreading of what the spec intended.)

[bigiain]

<meta discussion about voting>

I worked out a while ago that the comments I expended least effort on were the ones that were most likely to get significantly upvoted (and also downvoted) - longer comments get way fewer votes. My theory is that a single, almost throwaway sentence is easier to agree (or disagree) with, and hence earn a reflexive vote-click. When I write a few paragraphs (or more) as a comment, particularly with researched links and/or data, and thoughts/commentary on those links/data, I get way fewer votes, either up or down.

My initial reaction to this "discovery" was to decide to post shorter and more concise comments. But a few moments of reflection revealed that for me that's a pointless change of behavior for two reasons: 1) I don't comment with the aim of getting voted up, and shouldn't change my comment behavior just because there's a metric to be gamed, and 2) because at least for me, the bulk of my karma has come way more from fortuitously being first to submit a popular link (mostly assisted by my non West Coast GMT+10:00 timezone) - since the karma to be gained from a several hundred upvoted submission is _way_ less effort than writing thoughtful comments - and it's clear people are gaming that to pump karma (who was it that posted a while back about seeing bots stalking their rss feeds to autosubmit new posts? patio11 maybe?)

As you can see, I'm rambling all over the place with this comment - almost certainly in a way that makes it more difficult for readers to chose whether to up or down vote, and I'll guess resulting in neither.

Possibly stupid idea floating around my head right now - what if the voting system allowed you to not just up or down vote a comment, but to selectively up or down vote paragraphs or sentences or sentence fragments? Maybe I could choose to upvote your "the article author's claim that the function mapping real pixels to CSS pixels is nonlinear (which I think is just a misreading of what the spec intended.)" and possibly downvote another bit (there's not actually any of your post I'd choose to downvote, but maybe for example the "I suspect I know why I was downvoted"), then choose how to split my 1 unit of vote between the bits I want to vote up and the ones I want to vote down, so I could say 2/3rds for the up vote and 1/3rd for the down vote giving you a total of +1/3rd of a unit of karma - and more importantly, giving you feedback on why you're seeing the voting numbers you are…

[Produce]

>I find it interesting that I was downvoted to the negatives, then you posted this reply, and then I got upvoted to the top. I wonder what the causation is there.

Take this as a sign that HN is going the way of Digg and Reddit, may they rest in peace.

As for the mechanism of action, I think it has to do with people having the need to feel special. The crowd does A, a lonely voice suggests B and people jump on the bandwagon to be different. In other words, it's a mild and misplaced rebellion against the status quo. I've seen this happen countless times on social news sites and it seems to be one of the glitches of the human brain. Follow the white rabbit...

[wmf]

Sorry, I mistakenly downvoted you. I only skimmed the article since I already knew the history of px, and then I misread your comment; I thought you were arguing the opposite position (which is indeed dumb and pedantic).

Of course, when you complain about being downvoted it shames people into upvoting you (sort of like when adults bully children into fake-apologizing for something they're not sorry about).

[javajosh]

You're right: this implies that a browser needs to render pixels at the edges of the screen differently than the ones in the middle to fully conform to the spec, particularly very wide (e.g. 30") displays and/or when your face is very close to the screen.

[gwillen]

Is anybody else having problems with notifo-based comment notifications? I am receiving them, but the links stopped working sometime between Jan. 22 and March 8.

[ars]

http://blog.notifo.com/notifo

[gwillen]

Oh dear. Thanks for the heads-up; this is sort of unfortunate since (as far as I know) HN doesn't provide any other way to be notified of comment replies.

[JoshTriplett]

Try http://hnnotify.com/ ; it works perfectly.