3D Vision, Magic Eye, and Jell-O

How on earth do those Magic Eye illusions work? In this video, we'll learn how humans see in 3D to get to the bottom of it. We'll learn about methods of depth perception, an algorithm for making autostereograms, and a physical model of binocular vision.
Become a Patreon member: / physicsforthebirds
Intro: 0:00
Depth perception: 2:02
DIY autostereogram: 5:34
Jell-O model of vision: 8:44
Thank you to Caleb Birtwistle for captioning!
Magic Eye: www.magiceye.com/
Bird motion parallax: wexler.free.fr/library/files/k...
Chameleons: link.springer.com/article/10....
Random Dot Stereogram: archive.org/details/bstj39-5-...
Autostereogram algorithm: link.springer.com/article/10....
Best book: Bela Julesz, Foundations of Cyclopeon Vision

[@InvaderMik]

For the longest time, I believed that those autostereogram books in schools were an elaborate prank my classmates were pulling on me. They’d pretend to see an image where none exists. Now I see how committed to the bit they are! They wrote an entire book, published multiple papers, and created this entire video on the science of this thing that I still can’t observe!

[@user-sl6gn1ss8p]

they actually had to create this channel and all previous videos on it just to make it plausible

[@alexm7307]

That's what aphantasia feels like until you learn what aphantasia is!

[@Chayat0freak]

I'm medically unable to see these because while I have 2 mostly working eyes my brain does not do the stereoscopic 3d bit to my vision.

[@gamemeister27]

​@@Chayat0freakMy mom has the same thing! She can only see with one eye at a time, even though both work fine on their own

[@thesoupin8or673]

This was incredibly worth it even just for the image of a chameleon with glasses on. Delightful

[@ShumaBot]

I'm one of those people that can go cross eyed on demand and could always see the picture in magic eye pictures. What I never realized until it was shown here was that you can use the same method to instantly see every single difference in "spot the difference" puzzles. I tried it and it genuinely feels like a newly unlocked (if not particularly useful) superpower.

[@ZanHecht]

It's great for comparing two lists of items too

[@Doct0rLekter]

I never felt like I had to go cross eyed to see them. I just look and unfocus my eyes slightly until the image appears

[@iveharzing]

It's also great for comparing code with someone else who made the same code but their code works and yours doesn't. (speaking form experience lol)

[@fuzzyeuka7897]

You'd need to do multiple jello pours to get the magnets to sit at the right depth. Base layer, then magnet layer.

[@HedgehogGolf]

I love that the background is an autostereogram of your bird logo lol

[@theBATgoesUPoh]

this really feels like unlocking a superpower. my only exposure to autostereograms before this were when i knew what the image was supposed to be, so i was able to just kind of let it happen. i knew i was capable of seeing the image, but i didn't know how. after watching this video, i can control it now

[@tehweez]

Grew up blind in one eye so never got to see the magic images. A friend of mine gave me one of these books as a birthday gift on my 19th birthday knowing full well I couldn't see the pictures. We had a really really good laugh about it, and it's still one of the most thoughtful gifts I've ever gotten.

[@MrL314]

I have never been able to visualize these before, and this video is the first time I’ve ever been able to truly make the effect happen! My mind was absolutely blown seeing it really happen for the first time ever

[@Leadvest]

I think the important part of the oscillator array example is that the fields don't need to be overlapping for the phase shifts to be discernable. Sort of like how the rhythmic activation of neurons can communicate phase shift fields as signals without the ganglia physically overlapping.

[@Max-px7jn]

Yes...yes....indeed....

[@Flopsaurus]

Representing what they eyes see as a bunch of tiny magnets together takes some serious abstract thinking

[@smoceany9478]

im sorry for watching this im not a bird i just like the videos

[@glacialbae]

Get 'im, boys! 🦃🐔🐓🐣🐤🐥🐦🐧🦆🦅🕊️🦢🦉🦤🦩🦚🦜🦖

[@rojnx9]

It was a very nice touch that you hid your logo as a stereogram in the background, and you didn't even mention it.

[@thespeedyyoshi]

It’s very clever ^^. It also took me a while to see 😅

[@yari_dawg]

that brain is way too wrinkly to be mine

[@xdarin_]

Finally, a use for my ability to cross-eye on command

[@the_real_Kurt_Yarish]

I am convinced that I am physically incapable of viewing these magic picture images. Which, considering I have myopia, astigmatism, and a lazy eye, is probably true, lol.

[@kiwipomegranate]

Same, I’m blind in one eye so I probably can’t either 😭

[@gus3000spam]

I also have myopia, astigmatism and a lazy eye, and I learned this year (at 30), that I just don't have stereoscopic vision. Like, my eyes don't talk to each other, my brain cannot compare the images my eyes give him and figure out a 3D view. This may be your case, the test takes 10 seconds of you staring at a piece of glass, you can ask your ophthalmologist about it !

[@tylerbird9301]

i cant seem to see the images either but i've only got a prescription of like -0.75

[@olle1153]

@@tylerbird9301I have astigmatism and I can see them

[@user-xj8wy4uu1q]

@@gus3000spamcool

[@El-Burrito]

I don't know if it's the same thing, but my favourite thing to do is play spot the difference, where you can put two almost identical pictures next to each other and then go cross eyed until they overlap and your brain gets used to it. It's then easy to look around at the image until it gets blurry, at which point you've spotted a difference. It's super cool cause you can use the same trick to look at two images that are slightly offset and it'll give a 3D effect, much in the same way this does. Edit: And I proved I left my comment before finishing the video since you do end up mentioning that

[@zimbu_]

That's an excellent excuse to give chameleons tiny, wonky glasses. Kudos to the scientists on that one.

[@VoidPants]

THANK YOU!!! i’ve never gotten those magic eyes to work until now! thank you for explaining what’s going on instead of just a way to achieve the goal

[@spacelem]

I find wall-eyed stereograms much harder than cross eye-ed stereograms, mostly because it's much easier to move the two images further. The image at 7:00 is (I think) wall-eyed, but the two pictures are so big and far apart that I cannot get my eyes to point that far apart. The best I can do is go cross-eyed and get an inverted image (I could edit the image to swap them round, but my GIMP skills aren't the best).

[@ivanjermakov]

I had to minimize the video and walk away from my monitor for 2 meters to be able to cross eye enough

[@NoNameAtAll2]

​​@@ivanjermakovyou mean wall-eye? cross-eye is easy - just put a finger between you and the screen, works for anything

[@ivanjermakov]

@@NoNameAtAll2 no, cross eye. There is a limit on how close I can focus and that was not enough for two pictures to form the third one

[@Gunbudder]

i LOVE these. my mom got me all the original books when they came out. i always stop and stare at them. i learned to unfocus my eyes at an early age so they were always very easy for me

[@Timmysthirdbirthday]

my grandparents had one of those magik eye books floating around for when grandkids would come over. i was the only one who ever figured it out that you just cross your eyes and it felt so simple to me but everyone else in my family thought my explanation was nonsense and the book was a scam

[@GuagoFruit]

Perks of the Cross eye method: you can focus any two images regardless of separation. Cons: images aren't typically designed to be viewed cross eyed so they're inverted in depth. Perks of the wall gazing/look through method: images are usually designed with this method in mind, so have correct depth. Con: you're limited to images narrower or equal to the width of your interpupillary distance. Also I found the cross eye method to be much easier to learn because the parallax distance (distance judged by crossing eyes) and focus distance (distance focused by eyeballs) is much smaller. And its perk of being able to view any two images is huge in comparison. It allows you to do "find the differences" for instance, even on big pictures, because the differences will flash out like a sore thumb.

[@glacialbae]

I also find that the look through method tends to hurt my eyes after a few minutes. I've always wondered if autostereograms could be made so that they stick out with the cross eye method. It's just so much easier for people to do.

[@livedandletdie]

@@glacialbae The fact that over 60% of people can't unfocus their vision in the first place intentionally, also contributes to the Cross eye method.

[@zacharynovak2180]

I had every magic eye book and I remember having to basically train myself to become walleyed/unfocus my vision. It’s possible to do on command even without the wall method but pretty difficult and slightly uncomfortable. Also can make people dizzy with the constant shifts in focus when trying to get the right amount of overlap in the image.

[@CXT14GamerMouse]

I am the exact opposite. Gazing into the distance is the easiest thing for me. I can do it on command and it does not feel different to looking a bit further away - no strain at all. Thanks for describing both methods! I always thought people were describing it wrong when they said they go cross-eyed. I will keep it in mind for the puzzles, even though it is very straining for me. Just trying it made me feel slightly sick right now.

[@iwanttwoscoops]

@@livedandletdieyeah the original post said that. Did you read it before responding?

[@JTCF]

Hell yeah, I love autostereograms. What helped me to understand how to use them is just regular stereograms, where you have two mages side-by-side with little differences, that when you go cross-eyed and line up those two images the image becomes 3d. After I mastered that, autostereograms were easy.

[@mishael1339]

I just imagined a stereogram of a blue robed and hatted mage and that made me very happy. Thank you for the delightful typo, no mistakes just happy little accidents :)

[@gaelonhays1712]

The oscillator idea helped, thanks for mentioning it.

[@DontYouDareToCallMePolisz]

yay, someone actually explained how to see magic eye images

[@yanikb.1312]

Again, this video is great and speaks to me in a special way. I had a very similar book from my parents when I was younger and had a lot of fun with them. I also figured the mistake-spotting technique out by myself because of that.

[@Draconis_Eltanin]

Wait, you're telling me they should pop out of the screen/page and not be carved in? Have I always looked at them wrong?

[@jogar0065]

It just another "mountain or valley" illusion

[@Atommagi]

@@jogar0065 It's not. There are two techniques. Either you cross your eyes as if you were looking at a close object, or you let them go parallel as if you were looking at a distant object. And a given picture has to be viewed with the correct technique.

[@lpnp9477]

Yes. They're designed to be embossed rather than engraved. I used to cross my eyes as a kid and enjoyed them being engraved for many years until someone taught me the correct method. Now I prefer them embossed.

[@Queer_Gabe]

I just need to say that I get immensely joyful with these videos! ❤

[@sebas31415]

The avian physicist is back!

[@thespeedyyoshi]

I always felt like I had a super power when I learned how to do these magic eye things ^^ And now I can explain (some) of the physics behind it. Thanks! (Also I like the clever use of your bird constantly in the background if viewed by magic eye. ^^)

[@josephlongfellow1244]

the background seen easily @4:37 is a stereogram of the Physics for the Birds logo

[@YYCUrban]

Well this was great being legally blind in 1 eye lol. My whole life ive never been able to see 3d or certain visual illusions, because I only use 1 eye

[@tiredko-hi-]

My comrade! Edit: though I'm not legally blind, I'm just blind in that eye.

[@techneti_um]

Right here with you

[@kiwipomegranate]

Same here!! My depth perception is shit lmaoo (also btw the definition of legal blindness is both eyes so you can’t technically be “legally blind in one eye,” don’t worry I said the same thing, it’s on some official accommodation documents too 😭😭)

[@filoteo]

I haven’t even made it past the ad yet but AAAAAAHHHHH I love magic eye

[@adrien5568]

No matter how hard I tried, I saw nothing other than a colour splash.

[@saschb]

I love your jello magnets, even if they didn’t turn out as planned ❤

[@convincingmountain]

i don't know why but i kept seeing multiple sharks in the example - seeing two or three sharks layered on top of eachother, instead of the single one as in the original depth map. i managed to get it up to 5 duplicate sharks floating in the void before my eyes started to really hurt... what's up with that? is it because the image width (40px) was too low, or too high? so funky. great vid.

[@uberthought]

I was with you right up to the impromptu eye surgery at the very end. :)

[@christianprice4049]

Hey, thanks for another great video. Although, it was a little unexpected when I saw a very familiar view. Hope you enjoyed the hike!

[@MrSparkefrostie]

I think for years I had the expectation to see a picture, your explanation helped me see it, but now I have a headache from looking at it too much 🤣

[@Chocomint_Queen]

One thing you neglected to mention is that the "walleyed" and "crosseyed" technique, while they can both _see_ the image, see it _inverted._ Most magic eye books are designed for the walleyed method, where you focus past the image, and so you see it pop out. But if you use the cross-eye method, where you focus in front of the image, you'll see it sunken in, instead; a shark-shaped divot in a floating plane. Some are designed for the cross-eye method, though, so then the walleye method gets it inverted. This is because, obviously, going walleyed diverges your vision, moving your left vision left and your right vision right, while going crosseyed crosses it, moving your left vision right and your right vision left.

[@laserbean00001]

This vid is truly Physics for the birds. I'm sure this would help someone out there understand this but i'm not a bird.

[@Stratelier]

One of the key differences between different autostereograms are whether they're designed for cross-eyed or diverged viewing, because they will yield opposite interpretations of depth. Also crucially, for diverged viewing there is a certain limit to the "tile width" beyond which your eyes' gazes wouldn't converge to any point at all, which (while not impossible) is far more difficult to achieve.

[@DaMedicWhoSezNi]

I love the picture you drew of the “human”

[@erictheepic5019]

The only way that Magic Eye things have ever 'worked' for me is in the way that they successfully make my eyes hurt and give me a headache. As for the advice given: Going cross-eyed makes my vision blurry; I can't go wall-eyed; putting my nose to the screen doesn't result in double vision; reflections on my screen appear 'double' and I can't focus them into one image (strabismus, I guess). I'm pretty sure I'm just screwed, and so I have to sit here and stew in my frustration and anger while watching this video. Yippee!

[@shythevans]

"Its a Sailboat!" - One of the clerks movies, I think.

[@plackt]

I’m the same - can’t separate fixation (vergence) and focus (accommodation), so can’t see MEIs. Very annoying as a stereovision researcher, as my colleagues can usually “free fuse” my stimuli to see what they look like in 3D.

[@edbop]

Ah man it is funny how you forget about things and when you are reminded it takes you right back. These were all the rage back in late 80s early 90s

[@lorlimann]

Often times you‘ll find autostereograms in scientific publications of inorganic chemistry depicting crystal structures of molecules

[@kalelsoffspring]

I never understood why people liked those black head removal videos, but sit me down with some jello magnet removal for a couple hours and I think I'd be just fine hehe

[@alistairlacaille]

Didn't know if this would work on a computer screen or not. Paused the video, and yeah, sure enough... Never had a problem seeing the image; it just takes a minute to decipher what it is because I'm basically following the outline of it until I can make sense of the thing in its entirety.

[@ichigo_nyanko]

Young Rival - Black is good has a music video where the whole thing is one of these. It's pretty cool.

[@Tips_7384]

I love your content, keep it up! Unfortunately I still couldn't see the 3d images after any of the examples.

[@youtubersingingmoments4402]

Love the physics and all, but can you start an ASMR channel? You have the most calming voice.

[@ClassicallyBC]

I enjoy stereograms. I have moved from puzzles into biology. Using two eyes for references. Fun maneuver for two people.

[@Asterism_Desmos]

These are very interesting, I thought it was the angle of viewing and not that there would be a technique OF viewing that unlocks the image.

[@Asterism_Desmos]

Also, this is now neurology and psychology for the birds lol

[@Amonimus]

To explain how I thought it works, one side is a photo of an object slightly rotated to the left and the other is to the right. In stereogram they are overlayed and slightly shifted horizontally. If both eyes look at overlapping image at the same angle as the rotations, they will overlap where they shoukd be and show an object visible from three sides. I never understood why stereograph look like that though.

[@zac9311]

The shark one was awesome. Once i had it i could look around freely without losing it, and it really looked 3d

[@DareTear]

7:20 omfg this made me feel something.

[@JohnLeePettimoreIII]

1. make clear gelatin with less water to make it more rubbery. 2. lay down a thin layer and let it harden. 3. place magnets. 4. carefully pour more concentrated gelatin over the placed magnets and let it harden. 5. profit.

[@lydianlights]

For people having trouble, the further away the images are, the easier it is, since you need to cross your eyes less to make them overlap.

[@GLITCH_-.-]

next time you do one of these images, you should invert the depth-map. all your images have imprints instead of raised details.

[@PotatoSofi]

"Some people can do this on command" Yeah... I used to enjoy a book like this when I was a kid XD

[@Arithryka]

11:08 clearly the book itself is an autostereogram and there are slight differences between the duplicate pages :P

[@arcticpenguin.]

I love physics and I was wondering if/what your college degree was/is? Im going into college soon and I was wondering

[@BuckFudweiser]

My 2nd grade teacher had one of these on his wall. I had the toughest time figuring it out, but when I did.... Oh boy.

[@Xld3beats]

Focus on something far behind the screen, then slowly try to focus on reading the screen. It takes some practice to hold your focus where you want it, but when you "spot the difference" you'll see these weird sharp/fuzzy spots, more noticeable if you wobble the screen

[@Zeero3846]

If you wear glasses, it can sometimes help if you take them off or put them on depending on how far away the image is when it "clicks".

[@pmnt_]

Now I want to try building an autostereogram with the "solution" depth map as tiling picture.

[@JohnDlugosz]

I notice you have an autosterogram as a background image in your title cards. Nobody else seems to be talking about it. Anyway, there is a cursed Perl script that generates autostereograms using ASCII characters, of an image you pass as an argument. Only thing is, the output is a functioning Perl script that works the same as the original.

[@alittlefella985]

I can only get the ones with two images next to each other to work, how do you do the ones where it's a single one?

[@adityachaudhari1579]

This might be the only video where i give myself multipe small scale headaches on purpose

[@bscutajar]

It's not the reason pigeons bob their heads. Motion parallex doesn't require head bobbing. Birds can't see well when in motion, and thus they must keep their heads as stationary as possible. So they bob their heads to move their eyes discreetly rather than continuously.

[@nyther]

I managed to do the cross eye on demand thing quite easily and I did managed to form the third image in the center but I never saw anything in the autostereogram, in the "find the difference" image I saw the differences alternating between each side. I wonder if I really have a depth perception issue... 🤔

[@Timmysthirdbirthday]

you rock

[@Fishman7]

I like how the "human" at 2:02 is just 3 birds in a trench coat.

[@daanroelofs119]

Oh my God, I thought I was the only one who used this to do the spot the difference puzzles insanely fast

[@AMan-xz7tx]

10:45 you're right, shifting frequencies wouldn't work, but OFFSETTING their on-off cycles would be exactly like the stereotypical depiction of 3d sonar and would work perfectly (especially if the LEDs fade out instead of just being ON or OFF)

[@agargamer6759]

I love stereograms!

[@elise3517]

I still can't see them, but learning how they work was at least fun T~T

[@ophello]

I love maghlkic eye.

[@appa609]

If you wanted the jello magnets to work you should have made a half depth layer of jello, embedded your magnets, then poured more jello to encase.

[@yjr4df758]

I perceive the depth map backwards, and then sometimes get an involuntary muscle reaction when I lose the illusion, I can't even move that muscle on its own voluntarily. I feel some parallax, though it's a static image, probably my brain assuming it will see parallax, but not actually seeing it.

[@rsilva918]

Great video as always , but man you needed a better title ,maybe the logo on the miniature , I took 2 days for to click because i didnt recognize the channel.

[@GanerRL]

i have yet to be able to see a single one of these illusions :

[@trysta73]

I can do side-by-side 3d photos without a problem but still can't seem to make these work. Rarely I can squeeze some depth information out of them with a lot of effort but it's always random garble that doesn't form an image so much as like the depth equivalent of noise or a repeating pattern. Briefly did get the shark, but inverted, but I think that's the closest I've gotten with these.

[@WizardOfArc]

This is totally my trick to “spot the difference” 😁

[@tegxi]

autostereograms are my nemesis. I can cross my eyes at will way better than most people can but the opposite motion just does not work and I have wasted so many hours of my life trying

[@tiredko-hi-]

KZbin recommended a random-dot stereogram video to me. You can imagine my confusion when all I could see was static since I'm blind in my other eye.

[@sordesmax6238]

6:10 your random dots stereograms don't work, images are too far from each other. with bigger one I can overlap only third part of images.

[@elton8135]

i saw the shark, after like 30 mins of trying all i could imagine, i put my face like 2 cm away from my 16 inch screen (the image was all the screen) when i tried to see it again after a while i had to try like 10 minutes, even with my prevous experience of where to position myself, and having finished your video, pls help i'm so sad i couldn't see anything else despite my best efforts. how close should the image be? how big should it be? am i trying to focus my vision to a further place than the screen? do your eyes don't put the image out of focus when trying to see a different depth than the image?

[@livedandletdie]

The Physics for the Birds image didn't work at all, not even when it was overlaid, although I could see the general structure of it. Mostly because it's too small of a detail to see and I have perfect vision. I can see the area where it is supposed to be, but the problem is that there isn't enough contrast in the region to suffice to create a good enough image of the letters unlike that Beautiful Autostereogram of that Shark.

[@Cimera42]

Not sure why, but when I look at the shark picture at the start, I sometimes see 5, 3 or 1 shark... Any ideas why?

[@thetotalfunction7736]

Magnets in silicone, placed at the correct depth via toothpicks, that can be removed

[@congruentcrib]

I still can’t see these. When shown the answer, I can’t see the image. The one at 6:58 … even knowing what I’m looking for I can’t find it.

[@belgaer4943]

I was usually able to figure out a magic eye image but it took a looooot of squinting and crossing my eyes to get there. Wish someone had just told me to cross my eyes just enough to line up the horizontal patterns.

[@patoconzapatos]

🍞

[@nerdwisdomyo9563]

🗿🍞🍞

[@amelted]

I still have never been able to visualize these, and certainly not from a lack of effort.

[@warriorsabe1792]

Unfortunately, I can't go cross-eyed without also completely defocusing, and my monitor doesn't have specular reflections to focus on, so I couldn't see any of the illusions really (except for the jitter-framed one)

[@roribune8162]

Holy shit i have that book. Not the magic eye one, the history of magic eye one.

[@plackt]

As a stereovision researcher, it’s incredibly frustrating that I can’t free fuse to see Magic eye illusions, or my own random dot stereogram stimuli.

[@absurdshitposter7705]

I can't see the autostereogram is something wrong w my eye

[@sadiesaurus54]

I truly could not get the random dot stereogram to show up, even using paper to block the opposite square so each eye really only could see their own square. It's like my eyes can't look at the same thing at the same time, like I'm just switching back and forth very quickly. Maybe it's just when I think too hard about it 🤷‍♀️