0941: "Depth Perception"

[Jourdy289]

Whoops, forgot Alt-Text"

"I've looked at clouds from both sides now."

OK, along with the idea is SICK. In a good way.
Um, no pun intended...

[Me321]

An amazing idea

[SteevyT]

I want to try this now.

[Taymon]

...Wow. Would that actually work?

If so, everybody should experience it at least once.

[echoechoecho]

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

[Jared the Great]

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

Seconded.

[riddler]

Try skydiving. You will see them from all sides, and occasionally from the inside

[TaylorP]

The shading on this comic alone makes it stand out, especially the last panel. The idea is also pretty cool, it's definitely on my list of xkcd-things to try. Others on this list include the lightning+kite+sand=glass and the roller coaster chess.

[madock345]

I think i might be too scared to try this, I keep remembering that in the Hitchhikeers Guide the worst torture imaginable was total perspective

[astrosteve]

Wow, would this really work? the biggest problem I see is isolating one eye from the other. I just tried holding my iphone in front of my eyes and couldn't find a spot where my eyes didn't see the entire screen.

[americablanco]

I could never help but think when looking at clouds that somebody elsewhere looking at the same cloud does not see the same shape I do.

There's a psychological term for this... but I've forgotten what it was.

I don't hink 300ft is far enough to get a significantly different... wait... I get it now.

[mcwaffles2003]

So if I did this with really small cameras close together with high enough resolution could i stand amongst bugs or maybe even bacteria?

[ysth]

Dude, those are just pixels right in front of your eyes.

[fynthase]

Don't think this is too realistic. The camera would photograph the clouds on the same side that we see them on.

[mcwaffles2003]

Don't think this is too realistic. The camera would photograph the clouds on the same side that we see them on.

well yeah but itd just appear as if massive mountains were passing in front of you, its not like we can see the other sides of walls either :/

[xybre]

I'd love to see if someone can make this work. I'm trying to think of complications, but nothing is coming to mind yet. Should work just out of the box. Naturally you still won't be among the clouds, but someone with a pilots license could wire up HD cameras on each wingtip and give us a hell of a show.

[Vnend]

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.

[curtis95112]

Wouldn't everything just seem smaller and closer?

That being said, wow....

[ESoergel]

WOW. I'm amazed! Fantastic comic Randall, really incredible idea. please Please PLEASE make a blag post about this with some more details on how to do it. Have you actually done it?

Also, I still want to try the

lightning+kite+sand=glass

as well.

[Sizik]

You can get an approximation if you're a passenger in a car on the highway, due to the motion parallax.

[warzauwynn]

This would work, and it's a fantastic idea.

In order to get a normal 3D perspective from a single vantage point, the distance between your eyes need to be about 1/10 the distance to the nearest subject in the frame. I call this distance the ocular separation, but it's actually called the baseline.

This is one of the biggest problems with 3d cameras and lenses, the baseline is simply too narrow. You get a slightly better idea with motion, but with stills you don't get much 3d perspective.

Another interesting thing is that our eyes are very forgiving of slight differences in Z alignment. We're so used to seeing from two perspectives, and having one sometimes see something that the other doesn't (eg: the rims of your glasses) that we're good at correcting slight differences. Because of this, the comics premise could more easily work.

Here's a photographic example of having to increase the baseline to get a 3d perspective of a large object: http://www.flickr.com/photos/warzauwynn/3880287244/


I think that with current laptops, this would be very easy to do, even if not in HD. HD would be killer though...

[colt45joe]

So... Can someone try this? And post the 3D Video result on youtube?

[Steve the Pocket]

Re: The first two panels: Yeah, I was just thinking the same thing about blimps yesterday. They look really small in the sky, but then I watch one land and my brain just goes "Whoa, what the hell?"

And the alt-text punchline is both terrible and wonderful.

[JamusPsi]

I don't think an Xkcd has ever depressed me so much. I have no binocular vision.

[picnic_crossfire]

Just stopping by to echo everyone saying PLEASE GIVE ME SIMPLE ACCESS TO THIS PERSPECTIVE.

Be kind and PM me when you have the results for me.

You don't have to.

[TaylorP]

WOW. I'm amazed! Fantastic comic Randall, really incredible idea. please Please PLEASE make a blag post about this with some more details on how to do it. Have you actually done it?

Also, I still want to try the

lightning+kite+sand=glass

as well.

I live in a ruralish area, so it wouldn't really be a problem to fly a kit in my back yard during a storm. Plus our house is a 5 minute walk from Lake Ontario, so we get some pretty good storms here. I was *so* close to doing it a few weeks ago since a big storm was forecasted. Unfortunately I had to be out of the house at the time, and when I got home it was already raining/thundering and I sure as heck wasn't going to launch a kite at that point. It would have been the perfect storm too, since it was literally right on top of my town. There was one lightning strike that was so close to our house that the sound made the windows shake.

[wingsofwrath]

My first thought upon reading this: "And how exactly are you going to align the two cameras?"
I had an old pair of army binoculars that had (due to a series of nasty bumps and assorted accidents) the two telescopes slightly misaligned. Even though the flaw was not noticeable with the naked eye on the examination of the instrument, the resulting mismatched image could give you a headache after merely 5 minutes.

[ijuin]

I'd love to see if someone can make this work. I'm trying to think of complications, but nothing is coming to mind yet. Should work just out of the box. Naturally you still won't be among the clouds, but someone with a pilots license could wire up HD cameras on each wingtip and give us a hell of a show.

I'm pretty sure that standard USB or Ethernet cabling can't handle more than about 100 meters without signal repeaters, so you'd need those as well as the power cords for the whole setup--or you'd have to set up a directional antenna for wireless over that distance, or else convert to an optical fiber signal for the distance and then back to an electrical signal.

[reedrichards]

Well, if we're looking for something simple, couldn't we just figure out a way to take two pictures like that simultaneously?

[Hughes]

roller coaster chess.

I did this at a Six Flags. First, I nearly burned alive keeping an entire chess set under a hoodie two sizes too big in the middle of the summer while waiting in line for two hours (It had to be on The Titan; nothing else would do.). Second, I got kicked out of the park because of an aptly placed security dude.

[dacheetah]

Try skydiving. You will see them from all sides, and occasionally from the inside

Done this. From the middle of a cloud, all you see is white in every direction. When combined with the wind rushing past at terminal velocity, and the fact that the tiny water droplets actually kind of hurt at that speed, it causes a bit of a agoraphobia. Once you drop below the clouds and you can see the ground, it's suddenly much more calming, although then you're into the actual rain, where the water droplets are quite a lot bigger, and more painful, so it's still a little stressful until the chute opens, then you just relax and enjoy the awesome view.

As for the stereo video, this does sounds like an awesome idea, and if someone doesn't beat me to it, I'm totally going to track down a pair of webcams and do this.

[otherthings]

I've built one of these.

Not the digital version Randall proposes here, but an analog equivalent. It's also a lot smaller, but it works pretty well.

It's called a Telestereoscope. Check it out: http://eyestilts.com

I considered using cameras and video goggles, but abandoned that approach early on, because even a pro-quality video camera strips out so much information (spatial and temporal resolution, dynamic range of brightness, saturation of color) that it would necessarily be a weaker experience than just looking at the world with the naked eye. Instead, I opted for a low-tech solution: mirrors.

The one we built for Burning Man had about a 10-foot interocular distance, or about 50 times the average human interocular. But you can get pretty spectacular effects even with a smaller one. With the 1/3-scale prototype, I was able to watch the moon set behind the hills, by which I mean: you can actually perceive directly that the moon is behind the hills. Neither model is quite big enough to resolve clouds the way Randall describes (so beautifully!) in this comic. But I doubt that you'd need an entire football field to resolve clouds in 3D. By my guesstimate, 10 or 15 yards ought to be enough.

You can build a small one yourself for about $10 worth of hardware: just clamp two mirrors onto a piece of wood with L-brackets, and be sure to leave yourself an axis of rotation so you can adjust the parallax 'til your eyes can converge on stuff. It's a fun weekend project, I highly recommend it!

[BAReFOOt]

I have to try that!
But I will point my camera to the same position of the camera that is the most far away from me! If that means it’s on Mars, then so be it! I’ll even include a time delay logic that takes the rotation and movement into account.

Imagine how it would feel to be a giant, more than 11 trillion meters big! (At the biggest earth-mars distance, for a human of 1.80m height and 6,35 cm eye distance [roughly])

[BAReFOOt]

I'm pretty sure that standard USB or Ethernet cabling can't handle more than about 100 meters without signal repeaters, so you'd need those as well as the power cords for the whole setup--or you'd have to set up a directional antenna for wireless over that distance, or else convert to an optical fiber signal for the distance and then back to an electrical signal.

Why so complicated? Just have two wlan cameras connect to your wlan-enabled little laptop in the plane, encode it to something small, and stream the video over your tethered mobile phone. Since nothing will block your view to the mobile phone towers this should work.

[Eebster the Great]

I could never help but think when looking at clouds that somebody elsewhere looking at the same cloud does not see the same shape I do.

There's a psychological term for this... but I've forgotten what it was.

I don't hink 300ft is far enough to get a significantly different... wait... I get it now.

Not to turn this into another Passwords discussion, but the coolest idea I have ever heard for a "security question" was "What does this ink blot look like?"

As long as the same ink blot is used every time (and it isn't shaped like something obvious), it should be resistant to most attacks while very easy for the real user to get without memorization.

[sarrel]

I wouldn't have set it up in glasses. Pixels that close to my eyes are just pixels no matter how I try to look at them, not to mention that it sounds like it would get painful after a while. It sounds much easier to just put two monitors next to each other and a piece of that thick foam presentation board in between them, then lean my forehead against it with one eye on each side. Much easier to set up and clean up in my opinion.

Still, I can't try this myself anyway since I have an eye condition so that my right eye won't look at anything unless my left eye is closed, so I don't really have any depth perception anyway. Sometimes if I squint with my left eye I can sort of pull it off, but I can't really keep that up. It makes it a lot easier to decide whether 3D movies are worth it or not though. If I had any depth perception I would probably try this with all kinds of stuff. It sounds amazing.

[Davoid100]

In order to see a 3D image, as Randall is doing here, you have to have two images that you somehow combine into one (with 3D glasses, a viewer of some kind, by crossing your eyes or if your images are small enough, by parallel viewing [like the magic eye books] ). If the images are moving, as with clouds, the images will need to be shot at the same moment or your brain and eyes will ache from trying to combine the different images. You could actually do this, see the 3D shape of clouds, by having two people approximately 50 feet apart shooting at the same cloud. This is for still images. Live, moving images make it much more complicated, with webcams, long cables or wireless broadcasting. You'll still have to have some way of viewing the images to make your brain combine them into one.

But he's right, it would be glorious to see...

[stib]

I'm pretty sure that standard USB or Ethernet cabling can't handle more than about 100 meters without signal repeaters, so you'd need those as well as the power cords for the whole setup--or you'd have to set up a directional antenna for wireless over that distance, or else convert to an optical fiber signal for the distance and then back to an electrical signal.

ahem.. WEBcams.

Aligning them might be tricky, but if they were able to be remotely panned / tilted you could lock them both on a very distant point like a star. I'm sure someone tricksy with OpenCV could automate this process.

And yeah, while increasing the interocular distance means that you have greater depth perception, it would also give you the impression that the clouds were teensy tiny. http://tinyurl.com/interoculardistance



If you think about it, that's a perfectly rational thing for your brain to do. If you have to cross your eyes to bring an object into coherence, then it follows it's pretty close to your nose.

[Dinoguy1000]

Am I the only one who read the comic title as "Death Perception"?

No, I have no idea where I got that from either. Maybe I'm just tired.

[tijis421]

YES. This kind of mind-expanding art and out-of-the-box thinking is EXACTLY why I read xkcd.

Great one, Randall. F-kin' great.