0941: "Depth Perception"

[beav]

elegant.

beautiful.

[Sweeney_Todd]

Imagine doing this with the CCTV mod in minecraft.

[gmalivuk]

In a calm summer night in southern Argentina I could actually (albeit only for brief periods) perceive the depth of the sky instead of the traditional "painted dome" effect.

No, you could imagine it. As stated before, even from opposite ends of Earth's orbit, it's not enough to actually perceive stars as being anything but all the same distance away from you.

But the weird thing is, the ones that are purportedly cross-eye are backwards for me, when I use the cross-eye method. (Just to be sure, the cross eye method is the one where you cross your eyes, right? Like with a "Magic Eye" autostereogram?)

Edit: wait, I think the magic eye style ones are actually straight eye. Why would anyone use the cross eye type? Straight eye stereoscopy is almost natural, cross eye is nearly impossibly difficult.

Yeah, Magic Eye (and other random dot type) stereograms are parallel vision. They can get away with it because it's possible to have 90% or so overlap between the images without this actually affecting the 3D effect. But when you're interested in not just depth but also actual surface detail, you can't overlap the pictures. Which means you either have to use small pictures close up for parallel viewing, or you have to use cross-eyed viewing.

For example, I could see both types just fine browsing through stuff yesterday on my netbook, but now I've got my other computer hooked up to a 52" TV, which means parallel viewing requires 3-inch or smaller images on a TV 8 feet away from me, while cross viewing even full-resolution images (i.e. ones where the pair of them takes up the entire screen) only requires crossing my eyes as much as if I were focusing on a point 8 inches or so in front of them.

[Rukh]

I thought this strip was so wonderfully drawn and shaded that it inspired me to finally register, just so I could share the 1920x1200 wallpaper that I made from the final panel. Copy and paste the url for the image:

http://img.photobucket.com/albums/v341/joshpettry/xkcd_depth_perception_1920x1200.jpg

[jbrownkramer]

Brian May, Guitarist for Queen, PhD Astrophysicist, and Stereography Enthusiast (I am not shitting you) has done something similar by taking two pictures from a moving airplane: http://www.brianmay.com/brian/brianssb/brianssbaug09.html . What a guy!

[bennyp]

Professor Steve Mann already invented this. He called it Big Eyes. See also EyeTap

[ikmig]

How far away would a rainbow seem to be? Would it even make sense, or would it "look" like it was behind you, if you tried to compute the distance?

[efodix]

Has anyone thought to upscale this experiment? You could take a photo of the night sky in spring, and then one more in autumn. Would that be enough to get a 3D feel of the nearest stars?

[gmalivuk]

Has anyone thought to upscale this experiment? You could take a photo of the night sky in spring, and then one more in autumn. Would that be enough to get a 3D feel of the nearest stars?

Yes, people have thought of that. No, it's not enough to notice any difference in even the nearest stars.

Both of these have been brought up repeatedly in this thread.

[Roberto Font]

I really love this comic, i think it represents very well many of the things that are part of the essence of XKCD and most of the ones I love, many experimental/scientific things, occasionally beautiful/breathtaking drawings, and that sense of melancholy/wonder that only the best ones leave you when you are finished reading/watching them.

[AbsurdWalls]

I'm wondering whether surgery could correct the misalignment, and lenses to correct the myopia...

(I signed up to reply to this.)

If those were the only problems then (in theory) you ought to be able to view stereo if you used a method similar to what's suggested in the comic. The misalignment wouldn't matter because you could move the image on the screen, and the myopia wouldn't matter because you could put the screens as close as you like to your eyes.

I don't think that will work though. You probably also have amblyopia, which is a condition people get when they grow up with one eye that was consistently less informative than the other. Basically, the brain learns to pay less attention to the signal from the inferior eye. There's not really a cure for it (yet) but there are some promising studies going on. I do research on amblyopes myself but I'm interested in using the deficit to learn more about normal vision rather than in designing possible cures.

If you tell me what city you're in I might know of somewhere that's looking to do treatment studies.

[fedusenko]

I took this while driving to a family reunion in tennessee yesterday. The photos are seperated by about an 1/8th to 1/16 a mile and I photoshopped the trees from the right to the left so that maintaining 3d perspective was easier (the trees were completely different due to the paralax). Check it out! Let me know what you think...

I am not able to post the hot link so you will have to control-paste it in. Sorry.

http://a1.l3-images.myspacecdn.com/images02/133/c6dca23c9c3c4e048c3fe7155b463657/l.jpg

[smaxt]

Sorry if someone got to this first:

You know what would even be better? Do this with a couple microscopes. 3D microorganisms FTW? Or do I misunderstand?

[AbsurdWalls]

Sorry if someone got to this first:

You know what would even be better? Do this with a couple microscopes. 3D microorganisms FTW? Or do I misunderstand?

http://en.wikipedia.org/wiki/Stereo_microscope

[BytEfLUSh]

Damn, I guess there are a lot of great 3D images in this thread, but I just can't figure out how to view those side-by-side ones. I've read a lot of guides on how to "get them to work", but still no luck... :\

Can you cross your eyes? Just do that until the two images overlap exactly. I find that they then 'click' into place and no effort is needed to keep the eyes in 3D mode

I've tried that, but I only managed to get a glimpse of 3D on two wikimedia images, just for a few seconds. I asked my friends to do it, describing it as something impossible to achieve, and guess what? The next day they come back to me with all sort of stories about their amazing 3D experience across a variety of websites (including, but not limited to, YouTube)...

I believe that my high blood pressure is responsible for this. I always have uncontrollable tremors, even with medication. I guess I need to stand still while looking at those pics...

[AbsurdWalls]

Damn, I guess there are a lot of great 3D images in this thread, but I just can't figure out how to view those side-by-side ones. I've read a lot of guides on how to "get them to work", but still no luck... :\

Can you cross your eyes? Just do that until the two images overlap exactly. I find that they then 'click' into place and no effort is needed to keep the eyes in 3D mode

I've tried that, but I only managed to get a glimpse of 3D on two wikimedia images, just for a few seconds. I asked my friends to do it, describing it as something impossible to achieve, and guess what? The next day they come back to me with all sort of stories about their amazing 3D experience across a variety of websites (including, but not limited to, YouTube)...

I believe that my high blood pressure is responsible for this. I always have uncontrollable tremors, even with medication. I guess I need to stand still while looking at those pics...

Stereogram Tetris raises my blood pressure: http://hidden-3d.com/games_stereogram_tetris.php

[Carnildo]

How far away would a rainbow seem to be? Would it even make sense, or would it "look" like it was behind you, if you tried to compute the distance?

Optically, a rainbow is infinitely far away from you.

[cernael]

To view the planets, you could place a telescope at the the Earth-Sol L3 lagrange point (with a communication relay at L4 or 5) and you could take the pictures (roughly) simultaneously. You would have to view the nearer telescope with a delay on the order of 45 minutes. This would of course be extremely expensive, but it is quite doable.

Howver, I'm afraid that even the closest stars exhibit an imperceptible (to the naked eye) parallax--only slightly more than roughly 1 arcsecond, even with the image sources separated by 2AU. (...) Like wobbly said, you would pretty much need to use a computer to enhance the parallax separation.

Why not place two satelites in the Sun-Jupiter L2 and L3 points instead? That way you get something like a 10 AU separation.

[jestingrabbit]

Why not place two satelites in the Sun-Jupiter L2 and L3 points instead? That way you get something like a 10 AU separation.

Cause they're full of asteroids?

[Sockmonkey]

Space is so stupidly huge that "full" of asteroids means so spread out that you have to hunt for them with a powerful telescope to find even one.

[gmalivuk]

Is this also true at the trojan points in Jupiter's orbit?

[GomoX]

No, you could imagine it. As stated before, even from opposite ends of Earth's orbit, it's not enough to actually perceive stars as being anything but all the same distance away from you.

No, I could perceive it. The same way I perceive depth in a flat drawing. Stereo vision is hardly the only mechanism for depth perception. Hopefully you are not too busy correcting people to figure it out.

[gmalivuk]

The same way I perceive depth in a flat drawing.

Perspective and shadowing, then?

[jestingrabbit]

Popping open the old WP on trojan asteroids reveals that the actual places that cernael wanted to put the telescopes are unstable equilibria that are both on the line through the sun and jupiter... less asteroids, but harder to stick around at.

[gmalivuk]

Ah, right. I never remember which L-numbers go with which points.

[Dmytry]

I've did something like that when I was little, using mirrors.

For stars, the common method is to take pictures on two opposite sides of Earth orbit. You'll also need very strong magnification. You have 2 angular seconds of parallax for 1 parsec distance.

[Dmytry]

I've made a 3D video with a lot of stars, cross-eye:
http://www.youtube.com/watch?v=-FjraRhfBIg

edit: also,

In a calm summer night in southern Argentina I could actually (albeit only for brief periods) perceive the depth of the sky instead of the traditional "painted dome" effect.

No, you could imagine it. As stated before, even from opposite ends of Earth's orbit, it's not enough to actually perceive stars as being anything but all the same distance away from you.

If you look at an image and close one eye, you may perceive depth because your brain would reconstruct the distances from the shading instead of parallax. With stars, when you can see great many stars and milky way, you have conceptual shift from 'some stars are bright, and some are dark', which is even correct (stars have different intrinsic brightness), to 'ohh my god it's full of stars, there's so many stars so far away'. You can perceive different brightness as depth, when you see large enough sample for your brain to conclude that it follows the right distribution for the brightness variation of points of light in random cloud.

[TaylorP]

I've made a 3D video with a lot of stars, cross-eye:
http://www.youtube.com/watch?v=-FjraRhfBIg

The visuals in that are fantastic! What did you make that with?

[Dmytry]

I've made a 3D video with a lot of stars, cross-eye:
http://www.youtube.com/watch?v=-FjraRhfBIg

The visuals in that are fantastic! What did you make that with?

My game:
http://store.steampowered.com/app/67000
It has built in 3D support, for anaglyph glasses, common 3D TV formats, and side by side. So I just recorded it as usual in the side by side mode.
(Unfortunately doesn't work with NVidia 3d vision, chiefly because of NVidia's lack of sane API and makes per-game hacks inside the drivers themselves)

[GulliNL]

When I see a full moon I always try to picture the state of Texas overlaying it (you know, like we all learn in middle school some time) and then I think of how small it actually is Then again when I imagine the distance between the moon and our earth I just realise how big Texas is

EDIT; or was it the USA? I don't remember, middle school is waaaaay long ago

Lemme guess...you went to school in Texas. Neither of my schools in California (third largest state) or Alaska (bigger than y'all down in Texas) ever tried superimposing my home state on the moon. I think Texans just have an infatuation with the size of their state.

Don't let me remind you that if you cut Alaska in half, Texas'd be the third-largest state. Or even better: wait until low tide and then cut Alaska in thirds, making Texas the fourth-largest state.

Here's a map: http://alaska.org/bigalaska/howbigalaska.htm

Well actually I went to school in The Netherlands, since I was born there But I believe you because I assume you have a greater knowledge of the size of your country than I have about yours.

But actually I came back here to say;
Maybe this device by Sony will help with the stereo view. HDMI, full HD and even sound! Hmm... what do clouds sound like?
http://www.engadget.com/2011/08/31/sony-hmz-t1-headset-hits-ifa-we-go-hands-on-video/
(bah I can't use url-tags yet )

[AlexanderRM]

He should have the stream available to the public...

Seconded.

Thirded, or however far we've gotten... I'm sure someone else has already thirded this but w/e.

[SeaBeecb]

Joni Mitchell!!!

[danielearwicker]

A string of Hubbles along Earth's orbit to do this for stars has been on every astronomer's wishlist for years.

We can still take it pretty far with just what we have available to the people of this board though. If a couple members who live hundreds of miles apart with high-speed net connections and good cameras both sent a feed to the same website...

Actually, truth be told you could do the same thing with just one user and a ground based telescope, with the 6 month-apart shots you would still get the 2AU interocular distance. That being said, as alluded to earlier, stars are REALLY freaking far away, so even 2AU might not do much. The planets will move too much during those 6 months to do anything useful with them, so in the end it might not be as impressive as it sounds at first.

But maybe...

The solution is simple. Look at the sky with your left eye. Then wait 115 million years for the Sun to travel halfway around the galactic centre, and then look at the sky with your right eye and try to remember what you saw with the left eye.

[Kapten-N]

While neat, I don't think that what he has illustrated there would work the way the final image indicates.

First, lets say that those are really low lying cumulus, and the figure is "only" two miles tall. Say my pupils are 3 inches apart and my height is 69 inches. That's 23 times my stereo separation.

23 times 120 yards is 2760 yards, or a little more than a mile and half.

Maybe that's a workable distance, maybe it isn't, but even perched on top of goal posts the web cams aren't going to give that perspective. For that they would have to be up in the clouds, at 2600 yards, in the clouds.

Neat idea, beautiful comic. Now someone go take the numbers and actual cloud heights and find a mountain ridge we can use to make it happen.

Dude. You completely missed the point. You're thinking that he tried to say that his view would be that of a giant standing among the clouds. The last panel merely showed how he felt when seeing through those cameras, however the actual view he would get would be what that giant would see lying down with it's head on the football field. The only diffrence is that in the drawing the giant is standing up and that is a valid way to illustrate the feeling in order to communicate it clearly to the reader.

[Maxpm]

I thought this strip was so wonderfully drawn and shaded that it inspired me to finally register, just so I could share the 1920x1200 wallpaper that I made from the final panel. Copy and paste the url for the image:

http://img.photobucket.com/albums/v341/ ... 0x1200.jpg

This is my new background. Thanks!

[wbeaty]

There's no app for this yet?

After all, all you need is software. And any video shot from a side window in an aircraft, or even a car. No? The frames? Time sequence is lateral position sequence?

OK, take a video stream and sample it from two places about 1sec apart. If your cross-country flight was going 500MPH, that's 730fps, so the two video streams will be hyperstereo shot from 730ft apart. SO YOUR HEAD IS 1000ft WIDE!

If the scene is distant landscape, it doesn't change much over a second, so the two video streams are left/right stereo. If you're not wiggling the camera, there's no L-R alignment problems.

Display them side by side on your screen. Depending on whether the footage was shot from the left or right side of the aircraft, you might have to view them crosseye or straight. Go fast-forward or reverse to slide your head across the tiny landscape. If you can turn them into anaglyph, then provide a checkbox for L-R swap. And a slidepot to vary the delay time (varies the size of your giant virtual head.)

Then go browse for vids of landscape shot from moving vehicles.

http://amasci.com/news.html

Oh, and here's guys who still haven't "snapped back."

Mountaineering accident: north face of Uxbridge Rd.
http://www.youtube.com/watch?v=9U0tDU37q2M

.

[willpellmn]

In favor! This kind of reminds me of http://vimeo.com/23205323, a time lapse video from the Canaries islands. Watching the clouds slosh against the mountain ridge was the first time my brain really understood, instinctively, that we live at the bottom of an ocean of air. I think this would be the same effect, but for space instead of time.

Aubri, this blew my mind. Thank you for posting it.

[ToonCuyvers]

Me and a friend of mine were so inspired by this comic we chose to do a school project about it.
We used 2 android devices and a wiimote to make a Head-Mounted 3D-viewer of an OpenGL scene.

http://pic.twitter.com/8XNMJv7x is a link to a picture of the final result.

Thanks for the idea!

[testicletesticle123]

looks like someone has done something similar: http://www.youtube.com/watch?v=gzgdP0AInXM

[koruga]

Correct me if I'm wrong, but can't you see the enormousness of clouds in an airplane? I know I have.