0941: "Depth Perception"

[bosonicyouth]

appreciated

[Alidor]

I tried making little screens for each eye once - Tore open an LCD Casio TV and strung the screen out on ribbon cable and fitted it into a custom-fit headset box. That's when I discovered that no compact lens configuration in the world can make a 1 cm distance feel like it's fifty yards away. I suppose if eyeglass technology had followed Moore's law then the last twenty years would have made this possible by now. As it stands, coarse grey hair and crows feet are all I have to show for my once-youthful optimism. There's still time though...

[musashi1600]

I figure the quote for the "Virtual World" project from Sid Meier's Alpha Centauri is apropos for this comic:

"What do I care for your suffering? Pain, even agony, is no more than information before the senses, data fed to the computer of the mind. The lesson is simple: you have received the information, now act on it. Take control of the input and you shall become master of the output."

-Chairman Sheng-ji Yang, "Essays on Mind and Matter"

[RAGBRAIvet]

In small words, this sounds just fuggin' awesome!!!

[Arancaytar]

This is an awesome idea and I want to try it some day.

Is ~100m really enough for stars, though?

[thomaskcd]

For still photos, this can be done quite easily from an aeroplane.

Take a series of photos out of the window, using some kind of burst mode to get them less than 0.5 seconds apart
Half a second is about 150 m, with a burst you can choose any multiple of this depending on how much depth you want.
Fire up iView and place the two images side by side on your screen.

Squint, fuse the images and enjoy.

[jatoo]

*edit: source + more http://www.flickr.com/photos/53241841@N05/with/5052955906/

[joshuaodunne]

Through a bit of Google-ing, I did find this:

http://flickriver.com/photos/kiwizone/4142140390/#large

Yet I can't help but think that maybe the way suggested in this comic would be somehow grander.

[cephalopod9]

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 :/

He really doesn't know clouds... at all.

[Red Hal]

*edit: source + more http://www.flickr.com/photos/53241841@N ... 052955906/

Right-Click->View Image->Zoom 150%->Cross Eyes->Focus->Pretty!

[tuxedobob]

So, going a slightly different way with this...

I could swear I've heard a duet version of "Both Sides Now" with either two female voices or the singer actually singing with herself, but I can't find it anywhere on iTunes. Can anyone help me find it?

[philip1201]

You can use binoculars to split your viewing cones, and then use two larger screens at a greater distance to get the same effect, if reading glasses and a smartphone close-by don't work.

[mekily]

I think that sometimes Randall just has a crazy idea of something to build, then writes a comic about it to get people on the internet to build it for him.

[tekNico]

I guess most people here is too young, but wow, no tip of the hat to the greatest Joni. Well, I had the song in my head even before reading the tooltip.

[emilv]

Why is the right camera displayed to the left eye and vice versa?

[Awesomeness]

what I want:
two imax cameras on 2 similar sized skyscrapers. fast forward so the clouds are moving through day and night for a week in the space of an inspirational song. the best 3d imax short movie ever

[AvatarIII]

*edit: source + more http://www.flickr.com/photos/53241841@N ... 052955906/

thanks, i actually often watch stereoscopic videos on youtube in 3D using a similar setup to the comic (i actually use the case for Tool's 10,000 days special edition, which has lenticular glasses and a bunch of steroscopic pics in the booklet*, rather than reading glasses, but i use my smartphone) i'm going to have to check out that pic when i get home

*

Spoiler:

http://www.ray3dzone.com/Tool.html

i just prop up my smartphone on the booklet area.

[kalleboo]

Hmm, my Android phone (Sharp SH-12C) has a 3D parallax screen (i.e. glasses-free 3D) that this would be perfect for. It would be pretty easy to at least take a megaperspective 3D photo - just take a photo, and then run a few hundred meters to the left and take another one, and use a free tool to combine into an MPO to view on the phone. If it doesn't have to be live, I could just borrow two HD video camera and set them apart and start at the same time, record for a few minutes, and then combine the two (the 3D video it accepts is just a 720p file with the two "eyes" squished in side by side).

Damn now I want to do this

[herbys]

Regarding the stars thing, if you ever wander through the southern hemisphere on a cloudless, dark area during a moonless night, you can certainly experience the depth of space with just a few minutes of concentration. Just lay on your back looking at the sky for a while. Af first it will look flat just as it has always done. But then you'll notice that in the middle of the milky way (which is much more visible and defined in the shouthern sky) there's an area that faintly bulges. That's the center of the galaky, visible behind the closer spirals. You can see a difference between the area with identifiable stars (the closer arms) and the part that's just a shapeless cloud. If you follow the arm to the sides, you'll notice there's a part that also somewhat bulges before becoming fainter. You are looking at the arm along its tangent. If you look up further to the zenith you will notice, slightly above the center of the galaxy you have already identified, two smaller foggy clouds, one clearly visible, the other one requiring some effort to discern. Those are our galaxy's two companions, the magellanic clouds, two separate, small, irregular galaxies that are floating not too distant to the milky way's center.
At some point, after reviewing all these parts of the galaxy and its companions, something will happen. You'll "get" it. They will no longer be stains in a painted sphere surrounding you, but you'll suddenly feel stuck to the side of a planet, looking not up but to the side, at the three-dimensional galaxy, edge on. You'll see the magellanic clouds floating above the center of the galaxy, which you'll clearly be able to see now, while you'll feel immersed in the arm of the spiral galaxy the planet is in, noticing how all the stars that surround you are just parts of the same spiral arm.
It is an amazing experience, and you'll never look at the sky and see the same. I did this two times in dark spots in the Andes, and once in the middle of the Pampas. No booze or drugs involved (and I think either of those might make the experience harder to achieve, at least in the same way I experienced it).
It is worth a ticket to the south.

[Dave]

Epic.

These are the XKCD comics I've missed over the past, what, year?

Big panels, epic drawing, thought-provoking rather than funny.

Good to see one of these back in the mix!

[futnuh]

Imagine taking your head and scaling it up so until your eyes are the distance apart of the cameras in the comic. From the perspective of this giant, what would the clouds look like? As many have posted, proportionally smaller and closer. This is how your brain would interpret the stereo image feed. This has been done for yonks with stereo aerial photography. Leave it to XKCD though to apply it in reverse to clouds.

[justasecond]

Great comic, I try to see depth everytime I see the moon. Works for a while usually, cool experience. Always ends with me thinking how sick it is that there were actually people WALKING there.

[liljohn118th]

To be fair, although the text of the comic says he watches "mountains" pass by, the graphic depiction shows what it would really be like - the clouds would look proportionately smaller. In this case, if you look at the clouds compared to the person, they're pillow sized.

I've received a dose of such perspective once before, in a way. One reason you have a hard time gauging the size of clouds is you have no frame of reference - no object nearby which you "know" the size of intuitively. Once, however, I got just such a comparison. I'm lucky enough to have a job flying, and once while flying nearby another airline-sized aircraft, I saw it pass nearby a cumulonimbus cloud - one I would consider on the "smallish" size. I had seen clouds like this many, many times before - only this time, I could intuitively grasp the fact that a cloud this size could fit, with no exaggeration, HUNDREDS, if not THOUSANDS of airliner-sized aircraft. Had a city skyscraper been nearby, it would have no doubt dwarfed it similarly.

To quote Neo.... "Whoa."

On a flip side, I've also thought of a way to try this out on a much, MUCH grander scale... think interocular distance of, oh, 6500 miles or so...

Point the Hubble at one point in the sky, take pictures at opposite points in it's orbit around the earth. And actually, since the Earth is also hurtling along quite rapidly at this point, you could do much greater distances than that. How about 2AU (two opposite points at Earth's orbit around the Sun).

Whoa indeed.

[liljohn118th]

Great comic, I try to see depth everytime I see the moon. Works for a while usually, cool experience. Always ends with me thinking how sick it is that there were actually people WALKING there.

Sounds like you left your criminal past behind...

[Vash]

This comic is pretty cool.

[BlackLotus]

I just wanted to say.
Wonderful

[J L]

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

Right, wonderful, I forgot about this! http://en.wikipedia.org/wiki/Technology ... ive_Vortex

It's mostly the same as "seeing Pan", a common trope in fantastic literature ... so maybe our lack of depth perception is our only shield against infinity

[Dave]

Great comic, I try to see depth everytime I see the moon. Works for a while usually, cool experience. Always ends with me thinking how sick it is that there were actually people WALKING there.

Indeed, and how it just hangs in the sky, floating round and round us. Obviously, when looking at the moon and thinking about depth, you're also inevitably thinking about just how big the damn thing is.

Blows my mind sometimes.

[willpellmn]

I have greatly missed the drawing style in this comic, which was prevalent in the first couple hundred XKCDs and then disappeared (the most recent example I could recall before today was "Lighthouse"). The simplicity and beauty of those images proves that Randall does have real art chops, and thus it depresses me how many of his comics feature crappy stick figures and jokes which are either incredibly nerdy or just not that funny. The last several weeks (apart from "Password Strength", which is on my cubicle at work) have been fairly tepid, for which he can hardly be blamed given the cancer thing, but this one is easily my favorite XKCD of the past year or so. I would love to buy a device which easily generates the experience he describes, but am far too lazy to do it myself.

[Dellwood]

So once the idea has finished blowing your mind, spare a thought for those of us who can not, have not and will never be able to perceive depth.

Because for us, everything we see is just like that backdrop, only we can't even so much as catch so much as a glimpse of the world in the way most others do, for that matter white mountains drifting through the sky.

[GulliNL]

Great comic, I try to see depth everytime I see the moon. Works for a while usually, cool experience. Always ends with me thinking how sick it is that there were actually people WALKING there.

Indeed, and how it just hangs in the sky, floating round and round us. Obviously, when looking at the moon and thinking about depth, you're also inevitably thinking about just how big the damn thing is.

Blows my mind sometimes.

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

[PFD Studio]

As a long time stereo photographer and long time XKCD reader, I can tell you that this method of shooting "hyper-stereo" is not uncommon. Using widely spaced sync'ed cameras has been around for a long time in the film world. I would like to know what smartphone and what software Randall used to juxtapose the two images. (Note: Hasbro makes a viewer, the My3D, designed for viewing side-by-side stereo images on an iPhone/iPod Touch.)

[najodleglejszy]

pity I don't have any HD cameras. nor smartphone.

ah well, even if it WOULD work, people with diplopia can't enjoy 3D movies :/

[kmellis]

With regard to the stars, this is possibly the main reason why the ancients (classic Greece) preferred the geocentric to the heliocentric model. They were well aware that the heliocentric model made much more sense in terms of the geometry of the motions described. But the first hurdle was the notion of the Earth in motion, which was possibly just too counterintuitive to be taken seriously. By itself, though, I suspect that wouldn't have been a sufficient objection.

In the Almagest, the classic description of the geocentric heavens, Ptolemy specifically mentions the heliocentric theory but says that in addition to the problem with the Earth being in motion, there's an additional problem. And that's the complete absence of any perceived parallax in the stars over the course of a six-month period (a period which would, in the heliocentric model with the Earth in orbit around the Sun, be the extreme distance traveled from one side of the orbit to the other). This implies that the distance to every star from the Earth at both positions is effectively equal and unchanging; which for their purposes and their notions of distance, implies that the distance is essentially infinite. (For our purposes this is true, too. Just because we learn about distances such as "four light years" and "one hundred light years" doesn't mean that we have any intuitive comprehension of these distances at all. For pretty much everyone, really. The distance from one side of the Milky Way galaxy to the other is approximately 851 quadrillion miles. Doesn't help? Right...because "quadrillion miles" just doesn't work, either. Sorry, there's no way we're going to make sense of these numbers in distances we can comprehend.)

The Greeks thought the stars were attached in some way to the inner surface of a giant sphere...they were referred to as the "fixed stars", as opposed to the stars which moved, i.e., the planets. The notion that the Earth was in orbit around the Sun would greatly simplify the geometry of the whole thing, and that was something that certainly appealed to the Greeks who so loved elegance. Don't think that they were terribly pleased with the epicycles people so often ridicule today (though, really, it's not the epicycles which are most problematic, it's the equants). But placing the Earth somewhere other than at the center of the universe, and putting it into motion, and making the distance to the stars effectively infinite...that was just too much to swallow. They weren't dumb. As Sagan said, extraordinary claims require extraordinary evidence. The Greeks weren't empiricists, but the sentiment is still relevant. We require a lot of convincing to accept something that is far outside our commonsense intuitions. Many things we learn in school and which most of us today accept are, nevertheless, deeply counterintuitive.

This is all with regard to observations with the naked eye. Telescopes can provide images with enough resolution to detect parallax of the nearby stars with respect to those much farther away.

[kmellis]

Because for us, everything we see is just like that backdrop, only we can't even so much as catch so much as a glimpse of the world in the way most others do, for that matter white mountains drifting through the sky.

That's not exactly true. While you may lack depth perception from parallax, you do have other depth perception. Parallax is not the only evidence our visual system uses to synthesize depth perception. There are other things which cue it, particularly focal length (which does so very strongly), relative motion (which does so strongly), and among others the apparent convergence of lines to infinity, which is the source of some very powerful perceptual illusions involving depth and and relative size perception. If you truly had no depth perception, you wouldn't be able to function in a novel visual environment, yet you can and do.

And this is why stereoscopic engineering to produce the illusion of depth in moving images doesn't work well for everyone with normal vision and downright poorly and painfully for some. It's, at best, a crude hack.

[Khaz]

This is the most novel and incredible idea I have seen this year. Even if it doesn't work, it's some ridiculously out-of-the-box thinking (to abuse a cliche).

Thanks for the stereoscopic images posted above. I was able to see them properly in about two seconds. For once in my life, I can honestly say that I have learned a useful skill from porn.

Yes, stereoscopic porn is awesome.

[Igor83185]

I've been an avid reader as long as I can remember (and every so often, I re-read most of the older ones), but this is the first time i've posted.

I joined the fora because of THIS comic.

The poetry of those final lines brought a joyous tear to my eye.
Thank you, Randall.

[Oktalist]

Imagine taking your head and scaling it up so until your eyes are the distance apart of the cameras in the comic. From the perspective of this giant, what would the clouds look like? As many have posted, proportionally smaller and closer.

Closer yes, and thinner (having less depth*), but smaller? You only scale up the distance between the eyes, you don't scale up the eyes themselves.

* But then we weren't able to perceive their depth before anyway (at least not by stereopsis), that's the point of why we're considering this.


Another way of doing this might be to construct a very long periscope, mounted horizontally, which one would look through with one eye while looking with the other eye as normal.

[CiDhed]

I know the 3d screen on my phone is a bit gimmicky but I love taking 3d pictures/videos. It just adds more detail to the picture imo.

[mitchb]

The Hyperscope and Pseudoscope Aid Experiments on Three-Dimensional Vision:

http://optica.machorro.net/Optica/SciAm/HyperScope/1986-11-body.html