I've acquired a new superpower

https://danielwirtz.com/blog/spot-the-difference-superpower

by wirtzdan • 2 years ago

1807 557 2 years ago

Wait, that's not crossing your eyes, it's uncrossing them. Ordinarily if you look at something nearby, your eyes aim at a common spot. But when viewing a stereogram, you need to convince your eyes to aim at a spot more distant than the subject.

This is easy with practice, however IMHO it helps to be significantly nearsighted. Then you simply take off your glasses, and can look at something nearby with infinity focus, which is naturally associated with uncrossed eyes.

I don't know whether it's possible to train yourself to diverge your gaze, i.e. stereoscopically see images that are separated more than your pupil distance. Certainly I can't do that.

semireg• 2 years ago

While intuitive, I’m not so sure. I look at the center line and slowly cross my eyes until the 3rd image slides into place and then I get focus lock. At no time do I feel my eyes uncross and go the other way. Hmm!

satvikpendem5• 2 years ago

See my other comment about cross view vs parallel view, looks like you can do one vs the other and the author can do the opposite.

vault• 2 years ago

Wow. Thanks to MarkusWandel I discovered I can focus images while crossing my eyes and finally understood your comment. I've always done the "uncrossing" since I was a kid.

teddyh• 2 years ago

Both work equally well if you just want to spot differences. Cross-eyed view is somewhat easier to do, since people naturally cross their eyes when looking at something close to their face, but there is no natural reason for one’s eyes to diverge. But cross-eyed view also gives a subjectively smaller image, and is also not the usual way autostereograms are made to be seen.

jodrellblank• 2 years ago

but there is no natural reason for one’s eyes to diverge.

When you’ve finished looking at something close to your face and your eyes need to uncross. So you do that eye movement while still holding the image close to your face. Note you are looking “past” where the image is. As long as the image is closer than your infinity focal view you can do this, it doesn’t have to be close to your face necessarily, Magic Eye posters on walls do work.

phailhaus3• 2 years ago

For spot-the-difference, crossing your eyes is more effective and easier to "dial in" than uncrossing them. You're essentially making each eye look at the opposite image. If you try uncrossing, then you need to make sure the images are at the exact correct distance to cause them to overlap with that technique, because you can only uncross your eyes enough to look straight ahead.

nemetroid• 2 years ago

Looking uncrossed at the images in the article on my phone, I can easily achieve the effect uninterrupted between fully stretched arms and about half that.

ses19842• 2 years ago

It’s a good thing that properly designed stereograms take this into account and don’t require you to uncross your eyes past that point.

seeekr• 2 years ago

Is that true? It seems that our eyes are mechanically capable of looking in divergent directions, what's the reason that we're not able to "uncross" them beyond looking straight ahead? (Edit: Anecdotally I can confirm for myself that I'm not able to do it, so wondering if there's anyone that can.)

satvikpendem5• 2 years ago

Note that there is a difference between crossview and parallel view. See this image [0] and try to overlap them. Depending on what you see in the foreground, that is the type of view you're able to see.

Basically, it determines whether the 3D view you're seeing from the stereoscopic pair is convex (pops out of the page) or concave (goes into the page). It is of course possible to learn both views but most people naturally see one or the other. You can go to r/crossview or r/parallelview depending on which one you see.

[0] https://i.redd.it/g5ilwgk99r781.jpg

alt2273• 2 years ago

I find that there are different techniques to seeing both.

If I stare at the image and cross my eyes until focus lock I get crossview where the image goes back into the page.

If I bring the image right up to my eyes and stare through it into the distance, then slowly move the image backwards into my gaze until I get focus lock, then I get parallel view where the image pops out of the page.

I have always wondered the difference between the two and why it happens. Thanks for shedding some light on it :)

EDIT: I have just managed to achieve both without moving my head or the image for the first time in my life! Just by trying to look further 'past' the picture into the distance, and then by slightly crossing my eyes and focussing at a point in front of the picture.

I have been trying to do this for 30 years, and it is only your explanation which helped me to do it. Thanks so much!

jasonjmcghee• 2 years ago

I had never done the parallel view before either- spent 5 or so minutes at it and finally got it. For me it's still takes a fair amount of effort to maintain it (unlike cross view that takes effort to stop seeing it instead) but the 3d looks way more impressive somehow. Like the Toronto crowd one- hadn't seen so much depth in a "magic eye" before

Terretta• 2 years ago

Note that for parallel viewing the left edges (or centers) of the images should not be farther apart than your own eye spacing aka interpupillary distance (IPD) sometimes just called PD.

That imgur may need to be shrunk depending on your screen for parallel to work.

jeffhuys7• 2 years ago

I can do both pretty comfortably, but there’s a definite bias to parallel, way easier for me.

krick• 2 years ago

Cannot figure out what is the difference. I can focus on both seemingly without changing anything, even though they aren't both in focus at the same time. But I don't know what I'm doing differently, I just move my eyes up or down, adjust a bit, and that's it.

satvikpendem5• 2 years ago

Which one is in the foreground vs background?

a1o• 2 years ago

A new way of doing git diff, leave both versions of the code side by side and cross your eyes.

louiechristie• 2 years ago

My thoughts exactly. Could be done with a git diff in a VR headset

xattt• 2 years ago

If you’re already spending the computing effort to create the VR image…

justahuman74• 2 years ago

I sure didn't expect there to be a plausibly work-related angle when I came to this thread

bicx• 2 years ago

New business idea: git diff, but it uses Mechanical Turk to hire an army of cross-eyed diff spotters.

waffletower2• 2 years ago

There is a wonderful stable diffusion prompt here.

satvikpendem5• 2 years ago

Somewhat related, but I've been using the Semantic Diff extension in VSCode, works better than standard git diff.

tom_• 2 years ago

It sounds like you mock, but: you can do this, or near enough, and you can do it already, and it works really well!

0. Pick suitable tool. Firefox works. Notepad++ works. GIMP works. Emacs, not so much, but if you use Emacs, you know that you can fix this

1. Load file A into a tab

2. Load file B into a tab

3. Close all other tabs

4. Hold down the tab switch shortcut key and note the result

For images this is actually pretty decent and I've used it a lot. Good for figuring out what the differences actually are when your image-based tests fail, and similarly after making a speculative change. Let your eyes do the difference operation for you. That's what they're there for.

For text: you'd be better served by some other kind of tool. But text is just an image with letters in it, so the same principle applies. It does work!

(I've previously read a blog post, link to which I of course now can't find, about how old-style Photoshop undo was designed with this sort of thing in mind. Instead of working through the operation queue like normal people, it simply switched repeatedly between previous state and current state - the idea being that you'd make a change that you weren't certain of, then press the key repeatedly to see before and after. No need to think. Thinking isn't appropriate here anyway. Just let your eyes look at what they're seeing.)

Damogran6• 2 years ago

I was really good at the random dot stereograms. This is a really cool recasting of that skillset.

alt2273• 2 years ago

I think thats the best part of this skill. Everyone did 'Magic Eye' images as a kid, but to be able to take that useless skill and apply it to something more useful and interesting is really cool.

ChrisMarshallNY• 2 years ago

Dammit!

I can't uncross, now!

https://www.youtube.com/watch?v=qaz2hxZLycY

Fauntleroy• 2 years ago

I'm not sure this works if you have astigmatism

mikepurvis2• 2 years ago

I did until it was corrected with LASIK a year ago, and I could still do magic eyes, both with and and without my glasses on.

ehayes• 2 years ago

I have a small astigmatism (and wear glasses) and I was able to do it, but I feel like if I did any more today I'd have a headache.

EvanAnderson• 2 years ago

Having similar acuity in both eyes made a huge difference for me. I'm somewhat astigmatic but was able to do this eye "uncrossing" trick just fine. I had a significant loss of acuity in one eye and that's what left me unable to do this (or to watch 3D movies).

edelbitter• 2 years ago

de-clickbaited: to spot minor differences between two images, view them like stereograms

erwincoumans• 2 years ago

That's fun, it worked for me as well. I could spot the difference in all images, including the 'impossible mode'.

etaioinshrdlu2• 2 years ago

Who's been doing this since they we're maybe 7 years old :)

tobr3• 2 years ago

Checking in!

I’m frequently baffled by how unaware most people seem to be about the absolute basics of how their eyes work. Like, people don’t even seem to be aware of how their stereo perception is largely made from two images, or any of the implications that has. I actively think about the two images maybe dozens of times per day.

graypegg• 2 years ago

Chill out, that's a bit of hyperbole isn't it? This is just a trick for doing a spot the difference puzzle. It's not exactly a daily task most people are thinking about.

Most people at least understand that stereographic vision has something to do with 3D perception because we've all closed 1 eye before.

jeffbee• 2 years ago

I figured everyone because I had a puzzle book that instructed readers to do this.

knallfrosch• 2 years ago

We've had these stereoscopic books with hidden images and I never saw any. So I've been failing at this since 7 years old – does that count?

lowdest• 2 years ago

Yup I used to do this with tile floors as a child.

ThrowawayTestr2• 2 years ago

Neat. If this isn't working for you, try on mobile. It's easier if the images are small.

dreadlordbone2• 2 years ago

This helped, thanks.

rufus_foreman• 2 years ago

You can also just back away from the screen. For the 3rd one I had to back up about 6 feet from my monitor before it clicked into place, once it is in focus you can move closer to see the difference better.

dreadlordbone2• 2 years ago

For some reason when attempting this my neck starts cramping

etaioinshrdlu2• 2 years ago

Who's been doing this since they were maybe 7 years old :)

ktzar• 2 years ago

I used to use that trick with some arcade game that was popular in bars in 00s Spain. People were just impressed!

FL410• 2 years ago

Very cool. Even the impossible mode one was relatively easy!

tunnuz• 2 years ago

That's so cool, thanks for sharing this. I managed to do all of them, in the impossible one I identified correctly the area, but couldn't pinpoint the difference.

rstarast• 2 years ago

that's why they mirror one of the images in "find the differences" in puzzle competitions, e.g. USPC https://wpc.puzzles.com/uspc2024/

schlauerfox• 2 years ago

reminds me of convolution operation.

doctoboggan• 2 years ago

I've been doing this since I was a kid as well. When I was younger some restaurants would have video monitors with games on them, and one of them was spot the difference. I essentially maxed out the score and still held the highest score when I came back in town years later. I wonder if its still around...

voidUpdate• 2 years ago

I've heard about this before, but I've never actually managed to do it until just now. I needed to sort of "tune the parameters" a lot so that my eyes were crossed but also focused, since I've had a lot of trouble actually getting them in focus when I'm doing it, and the effect isn't as pronounced as I expected it to be

idiotsecant2• 2 years ago

I think you're still not doing it quite right. The effect is really quite obvious and pronounced.

piva00• 2 years ago

It took me some attempts but I agree, it's very obvious, the 2nd image made it glaringly obvious after I managed it well on the 1st one.

My eyes get very watery after just a few seconds though, curious to hear from others how common this side-effect is.

TonyTrapp• 2 years ago

Doesn't work for me. Just like stereograms. I just don't know how to "tell" my eyes to cross. Maybe similar to how I didn't figure out until I was 20-something how finger snipping works. Maybe by the time I'm 50 I can cross my eyes...!

dgacmu• 2 years ago

To do it with crossed-eye view, try looking at your finger and slowly moving the finger closer to your eyes until you see a third image come into view in between the two on the screen. At some point your brain will/might let you focus on that image.

alt2273• 2 years ago

You dont 'tell' your eyes to cross, you just look closer or further away. Try looking at the image at normal distance, whilst imaginging that you are looking into the distance at a beautiful view or at the horizon on an ocean. It is this difference in distance focusing which causes the illusion.

s3krit• 2 years ago

Actually, given enough practice, you can literally just get your eyes to do it. I started doing magic eye puzzles as a kid and loved it, so just eventually learned how to control my eyes in that way. Even today, if I see any repeating pattern, or even anything vaguely similarly shaped, I can’t help but do it

Karawebnetwork• 2 years ago

Whenever I try to do this, the most I get is that the two images touch. The cats in the example are holding paws, but they never overlap. I've been trying to make this work since the old magic images from the 90s, but I've never managed it. I wonder if there isn a hardware limitation related to my eye configuration.

JTyQZSnP3cQGa8B• 2 years ago

Well actually, I've been telling my eyes to cross since I was a child. I can't describe it, it's like tensing a muscle in the eyes or something and you can control the angle with the tension.

dspillett• 2 years ago

The never work for me because my eyes don't work well together. Just not team players. I'm almost always looking through just one or the other, annoyingly usually the one that would least be preferable.

SysComp• 2 years ago

Not working for me

the__alchemist2• 2 years ago

If you've done Magic Eyes, this is straightforward. Was able to get all 3 of the test images quickly.

This is with focusing beyond the screen. Focusing in front of the screen is something I am unable to do, and not for want of effort.

Also, your eyes might accidentally do this if looking at tiled patterns, e.g. wallpaper.

Relative image size (e.g. view distance) is important.

mikepurvis2• 2 years ago

I have a slightly lazy right eye, so this has always come naturally to me, but I will say it's considerably easier to achieve the false focal lock on printed material— something about screens, even quality ones with high refresh rates, just isn't the same.

johnthedebs• 2 years ago

As a kid, I got a Magic Eye book and learned to see it by crossing my eyes (ie, focusing in front of the screen). I thought it was pretty interesting when I realized that I was seeing all the images inverted ("peaks" were "valleys" and vice versa) due to the way I was focusing. Alas, I never was able to see the images "correctly".

ses19842• 2 years ago

Instead of crossing your eyes to focus in front of the image, you have to uncross them and focus on something behind the image. Put your finger about six inches in front of your face and then look at the horizon. If the horizon is in focus you should see two fingers.

andrewla• 2 years ago

Same -- much harder to get them to go the other way. I'm surprised that cross-eyed random dot stereograms never took off; so much easier to do.

kayge4• 2 years ago

It's funny because even if you do the Magic Eye pictures "correctly" (focusing past them) you can still get funky images by going too far and locking the surrounding pattern a second time. If I remember right the first time I did this was on a heart picture (similar to [0]), which ends up looking like a big puffy W stacked on top of a slightly larger puffy W :D

[0] https://i0.wp.com/www.magiceye.com/wp-content/uploads/2018/1...

SoftTalker• 2 years ago

I can get the images to merge but the differences don't stand out.

the__alchemist2• 2 years ago

Are you able to confirm the images are completely aligned? You can do this using landmarks, like the brightest stars on the telescope pic. I.e. if you see more than one of any landmark, it is not aligned. You may need to adjust zoom, and distance from face.

mNovak• 2 years ago

I find there's a two step process, first overlapping the images (but which makes the images blurry), then letting my eyes refocus so the middle image is crisp. Only then does 3D or shimmer effect happen. Takes some practice to merge the images while maintaining focus for me.

layer83• 2 years ago

I’ve done Magic Eyes a lot, but I’m failing on this. (However, I found the difference in the coffee beans picture reasonably fast without the eye-crossing trick, and before reading what the difference is.)

adeon• 2 years ago

Maybe we are the opposite. As a kid, I could only do cross-eyed-focus-in-front-of-screen, but not "focus beyond the screen". Or a book at the time.

So I was able to see the 3D in Magic Eyes, but the 3D effect was inverted.

Today as an adult I am able to focus beyond the screen, but it's still much easier for me to do it cross-eyed.

I also got all the images in the post almost right away. But my eyeballs focused in front instead > _ <

naet• 2 years ago

I'm great at magic eyes / stereograms and have a ton of posters around my house with them, but I still had trouble with seeing the differences in the test images. I easily locked in my focus on the overlapping cat images but only one difference stood out to me. I eventually got them all but it wasn't that easy (maybe with practice I could get there). The differences are noticeable when I focus right on it, but when I'm looking at the whole image it's harder to tell what is missing from one eye.

manbash• 2 years ago

Are you able to look around while keeping your "unified vision"?

To me, all the differences appeared to be flashing (probably my brain alternates between the pair of images it attempts to "lock in", or something to that effect).

crazygringo• 2 years ago

Yup, I loved Magic Eyes as a kid. This was easy.

Nevertheless, I was astonished that "impossible mode" literally took me only 1-2 seconds to find the missing star.

Like, I knew our vision is good at interpreting depth from images. I figured it would be all right at finding large areas of differences. I had no idea a single freaking pixel could stand out like a sore thumb.

sailfast2• 2 years ago

I had trouble finding the "shiny" pixels on that one simply because the stars also had that issue - but after enlarging the image a bit more and scanning back and forth I was able to pick things out a bit better.

Now, ask me to look at my code again for a couple minutes and it might be tough but it worked :)

irjustin3• 2 years ago

How do you do this focusing beyond the screen!?

I'm trying so hard to make this happen. Stare really far in the distance and then move the image in front of my face on my phone. No matter the distance between my face and my phone i can't overlap the images.

Focus in front of the screen is the easy one. How do you get beyond....

ninetyninenine4• 2 years ago

You know how you can make your eyes see double when you cross your eyes a bit? Do this and you get 4 images. Combine align the center 2 images and your eyes will automatically “lock on”.

gcanyon2• 2 years ago

I can do magic eyes, but this technique doesn't work for me. My left eye is dominant enough that the whole image just looks like what my left eye is seeing.

ddxxdd• 2 years ago

I challenge you to use this refocusing ability to pass the Stroop Test: https://faculty.washington.edu/chudler/words.html

You are given a list of color names, written in font colors that are incongruous with the written word. E.g. "Red" will be written in a blue font, and "Green" will be written in a yellow font.

You have to say the font color and not the written word.

It's challenging, but it's yet another application where going cross-eyed confers an advantage.

whywhywhywhy• 2 years ago

This same technique can be used for a 3D effect: https://old.reddit.com/r/CrossView/

not_a_bot_4sho• 2 years ago

Every Asshole knows this trick for targeting spacecraft

https://youtu.be/XGdjKvivJA8?si=lRrfl6rHzAsE7nEO

robofanatic• 2 years ago

Thanks! now I have a migraine

chrisbrandow• 2 years ago

Every 80’s kid knows this trick from those old books where you cross your eyes to reveal images.

tobr3• 2 years ago

More things you can use this for:

”Are these two things the same size?”

”Are these things that are supposed to be evenly spaced actually evenly spaced?”

”Are all these things straight/at the same angle?”

”Is the wallpaper pattern aligned everywhere?”

”Is that surface using a repeating texture?”

dredmorbius3• 2 years ago

I may originally have stumbled across this trick looking at repetitive patterns. I distinctly recall automobile upholstery (with a regular recurring ventilation pattern). In particular, abberations in the pattern (dirt, missed holes, etc.) stood out.

Similarly, acoustic ceiling tiles, repeating patterns on wallpaper, rugs, or draperies, building faces, etc.

This may be a superpower to some, or a supertorment to those with OCD ;-)

OscarCunningham• 2 years ago

This is called 'vdiff' in the Jargon File: https://jargonfile.johnswitzerland.com/vdiff.html

Jzush• 2 years ago

I didn't know this had a name or was considered a skill. I've done this since the 90's when those magic eye books became popular.

I even managed "impossible mode" in 2 or 3 seconds.

Workaccount2• 2 years ago

At a local bar they had a game machine, and if you got a high score on any of the games, your tab for the evening was free.

One of the games was a "spot the differences" between two pictures with an ever decreasing timer for each round. Using this trick I was able to easily surpass the high score, and garner a crowd watching me perform this mind numbing feat.

Probably my peak fame right there.

soco2• 2 years ago

I can't overlap the images to save my life - they get like halfway there and that's it...

ThrowawayTestr2• 2 years ago

Try on mobile, it's easier if the images are smaller.

physicles• 2 years ago

Are you crossing your eyes (focusing nearer than the object) or diverging them (focusing past it)? Diverging is a harder skill to learn.

waffletower2• 2 years ago

That happened to me too but I persisted and eventually succeeded. I think I needed to cross my eyes slightly more than I was initially. I have been diagnosed with a minor eye convergence issue which makes it difficult to focus on near field objects in motion -- gaining this superpower was difficult but I did it without a headache thankfully.

PaulHoule2• 2 years ago

It's like

https://triaxes.com/docs/3DTheory-en/522ParallelCrosseyedvie...

which some people struggle with, somebody posted a

https://en.wikipedia.org/wiki/Autostereogram

to HN yesterday which some people get and others don't. (That's different from the "cross-eyed stereogram" because one of them involves having two images and the other one has one image with two images hidden in it)

rwmj• 2 years ago

I spent far too much time as a twenty-something generating autostereograms, which seems to have trained my eyes. I was able to "cross" the images on this page very quickly.

jeffhuys7• 2 years ago

Don’t CROSS them. Relax them, like you’re tired and can’t focus on a computer screen.

Taek• 2 years ago

You might be too close to the screen.

Tempat• 2 years ago

If you mean literally you can only bring them half way together, try just moving twice as far away.

adamc2• 2 years ago

Yeah, me either. My eyes really resist it. And after trying it a few times it messes up my focus for a bit.

nadis• 2 years ago

Same! I feel like I can get a fleeting moment and then it's gone. I swear I could cross my eyes when I was a kid - I wonder if with practice it'll come back or if I'm just old and this skill I didn't-know-I-wanted is lost

smusamashah4• 2 years ago

There is a way to help yourself.

Put the pair of images in front of your eyes.

Bring your finger between your face and the image.

Now look at your finger.

Move your finger back and forth.

While doing this, notice that at a particular distance, the images in background will perfectly overlap each other.

That's your moment.

Pull out your finger and look at that image.

---

Should take lot less tries to learn doing it without finger. I have taught cross eye to my siblings and cousins using this method. But if you always need finger to focus it's fine.

lr4444lr• 2 years ago

Treat it like a "Magic Eye" photo and just relax your eyes to a further focus point.

hgomersall2• 2 years ago

When it works you get what seems like 3 images with the middle one showing the differences; you can then relax and peruse the middle image at will. I guess all the practice with SIRDS as a child probably helps.

loco5niner• 2 years ago

Here's another trick: open the image in a browser, then zoom out. The smaller the image (up to a point and you can find a sweet spot) the easier it is to get them to overlap. Once you've got it, slowly zoom in a bit at a time, re-acquiring the overlap at each stage.

prashnts• 2 years ago

What really helped me was doing some sessions with an Orthoptist to reeducate my eyes. I used to see double when stressed sometimes and could never imagine to converge/cross my eyes and retain focus. With the reeducation I was able to see the Impossible one in focus after a couple tries.

OzFreedom• 2 years ago

Same as in autostereogram, the trick is to look to the distance. Close your eyes and imagine a mountain far away or some distant object, notice how your eyes adjust to see it. Open your eyes and try to look at this imaginary mountain while the image is in front of you. When you see the third Image, treat it as if its a distant 3d object somewhere on the horizon.

Ericson23142• 2 years ago

That was me at first.

I think the "cross eyed" phrase is a bit ambiguous.

What I ended up with (I think) is a focal point not closer than the screen but farther than it. My eyes didn't want to do it at first but then they did.

What is weird about it is the focusing and focal point are out of sync --- my brain can do it but the weird feeling is one of "gosh, this thing is a lot closer than it should be" where "should be" is based on focal point, and "is a lot closer" is based on focus.

Don't want to do this too much, feels like I could easily decalibrate my brain for real life lol.

hoppp• 2 years ago

Works for me, I see 3 images if I try hard and the differences pop out

smusamashah4• 2 years ago

I have just figured that using kitchen towel rolls as a binoculars is the easiest way to do a parallel eye on these kind of images.

Try that.

Hold the rolls like binoculars where right roll is pointing at right image and left is at left image.

It's like a DIY VR headset where your brain/eyes only gets two same looking things to focus. No outside noise.

duxup• 2 years ago

Probably my peak fame right there.

My son and I always make jokes about everyone's 5 minutes of fame. Some random person on the jumbotron at a sporting event "Yup, there's his moment, it's over now."

At least yours got you something ;)

klondike_klive• 2 years ago

One of my dad's sayings when somebody in a film delivered a line and then disappeared was "6 months rehearsal for that."

scrozier3• 2 years ago

You may or may not be aware that Andy Warhol famously quipped that, "in the future, everyone will be famous for 15 minutes," back in the late 1960s. As media has gotten to be ever more ubiquitous and the cost of entry lower, he was clearly onto something decades before the internet!

warner256• 2 years ago

Totally indulging in this side discussion: I remember thinking in high school and college that fame was the end-all of life, telling people that my goal was to have my own Wikipedia page. I saw it as something like the combination of being a "cool kid" (but for, you know, the whole of society instead of just one's school) and a sort of immortality.

Anyway, over the last couple of decades as an adult, besides realizing the obvious - how terribly shallow that is, and missing so much of what's really good in life - I've realized how fleeting fame seems to be even for the truly famous. Even looking over the list of US Presidents (never mind lesser political figures like VPs, cabinet members, congressmen, etc.) as someone who has always been interested in history, I look at some names and think, "who?" or "I've heard the name, but know nothing about him." I mean, of course you can still read about them, but that even a US President can be largely forgotten as a household name within 250 years is really a stunning thing to think about; they are ultimately no more immortal than someone who only has their name in a genealogy database or on a grave marker.

animal531• 2 years ago

I once accidentally dropped a glass that was about half full of water and I somehow managed to catch it with the side of my foot without spilling any.

Sadly no one saw this 'feet'.

throwaway743• 2 years ago

Just got a funny visual of someone going crosseyed and focused on overcoming a challenge in front of them, with a crowd of people cheering them on.

lxe2• 2 years ago

I was about to post this same exact post :)

Was the high score holder on there for a few years.

sschwa12• 2 years ago

This is my peak fame as well. I had the high score on every one of these I've played using this method. My friends were always try to figure out how we could make money doing it...

The game is usually called 'Photo Hunt'

bluedino2• 2 years ago

Those Megatouch systems run Linux! Lots of fun messages to read on the credits screen or when you reboot them.

lenkite• 2 years ago

Failed to perform the technique despite multiple retries, but didn't have any issues spotting differences the normal way for all except the impossible mode - which just felt like it would be tedious.

My usual method is just to brute-force linear scan from left to right, top-to-bottom. May not be elegant, but it works.

redcobra762• 2 years ago

...except as you say, it didn't work. The "eye-cross" trick gave the answer on the impossible one in ~10 seconds.

ElijahLynn• 2 years ago

Took me about 10m total to get it all the way to impossible mode. I think you can do it!

K0balt2• 2 years ago

Fun fact- when I was a teenager, my friends and I set up a stand in a local mall selling those “magic eye”posters. We made bank for a few months. But, there are actually a lot of people that medically cannot use the technique, or at least for whom it is extremely difficult or less vivid. Severe astigmatism, (obviously) blindness in one or more eyes, and certain attention deficits or fidgety types often have a difficult time.

I, on the other hand, 37 years later,am basically permanently crosseyed from the experience lol. It somehow became a resting state for me from all of the practice, so I’m always doing it on any kind of repetitive patterns, and even “successfully” on random ones which does some really weird stuff in your visual cortex.

mcv• 2 years ago

Same here. I can get the images to overlap; it feels like a stereoscopic image that lies a bit beyond the screen. But the differences don't pop out to me. I have less trouble finding them looking normally.

144• 2 years ago

Sadly I was never able to gain anything from this trick other than my kids admiration. Often times kids menus at restaurants will have a spot the difference and I can see everything instantly doing this. Impressive to a kid but this girl in the video was obviously doing the same thing and does not impress me.

codazoda• 2 years ago

Weird timing. I dunno why this works but I've been using it to see mice.

You see, I noticed that I have a mouse problem in my garage. I figure if I've seen one mouse, there are probably more. So, I stood on some stairs in my garage and crossed my eyes to sort of blur the scene. It allowed me to catch movement more quickly and I was quickly watching multiple mice run around the edges of the area.

idiotsecant2• 2 years ago

That seems like not the same thing though, right? You're not doing a diff on two images, you're just losing resolution so you can direct more attention to movement.

thunderbong• 2 years ago

I think it's because our peripheral vision is able to observe movements faster.

mncharity• 2 years ago

Hmm. I noticed in lectures, if I stilled my eyes, most of the field of view would grey out, except for areas of motion (eg a lecturer's head or writing arm) which appeared normal. After motion stopped in an area, it would slowly grey out. When a motion started, its area would snap to normal, making it easy to spot onsets of motion. Eventually my eyes would twitch, and the whole field would refresh.

iamjackg2• 2 years ago

I've done this in the past with bugs in the grass. If I stare at a fixed point, I start seeing each individual bug moving through the grass, whereas normally they would be really hard to spot among all the fine details of the ground and grass blades.

athom2• 2 years ago

I first read about this back in the 1980s, in an issue of Science Digest. Couldn't find a link or reference on short notice, but here's something from the American Academy of Ophthalmology that explains the phenomenon, with an experiment to see the blood vessels in your eye:

https://www.aao.org/eye-health/tips-prevention/experiment-se...

Apparently, the brain tends to ignore visual stimuli that don't change over a short period of time, which allows you see "around" the blood vessels passing through the middle of your eye. By closing your eye, and moving a penlight around against your eyelid, you can make the vessels cast a shifting shadow on your retina that makes them visible.

The reason you usually see everything out in front of you is that various actions cause your eye to shift about just a little, just enough to cause the image on your retina to shift about enough for the brain to notice.

yegle• 2 years ago

I feel old knowing https://en.wikipedia.org/wiki/Magic_Eye

egypturnash• 2 years ago

You can also now free-view stereo image pairs. Congratulations.

robotguy• 2 years ago

When auto stereograms were all the rage in the late 80's I had a program on my Mac Plus that let me make/edit them and I used to edit for hours WHILE looking at them in 3D. Then one time I was walking down a hallway with a repetitive wallpaper pattern, my eyes did the thing, the entire hallway appeared to shift in front of me, and I stumbled and fell. Still to this day my eyes will sometimes automatically snap into 'alternate' focus when viewing a repetitive pattern.

shaftway• 2 years ago

This happens to me too. Particularly when it's on a narrow horizontal repetition (like wooden slats on a wall).

I attribute mine to playing a lot of the game Magic Carpet from the mid to late 90's. It had some interesting graphics modes, including Red/Blue anaglyph 3D and a stereogram 3D mode. It was fun to try to play it, but it used noise for the pattern, so you didn't get textures, only blobby shapes.

wruza3• 2 years ago

This happens to me easily inside cars with these dotted-breathing roof interior patterns. (Edit: g “perforated vinyl fabric”)

Well, worse than easily - sometimes I cannot get back to normal and am not sure how far it actually is, because the nature of the pattern allows to re-lock at every few cm. I just don’t know where I’m really looking at unless there’s an irregular object nearby.

floydnoel• 2 years ago

I don’t share a lot of comments from HN with my spouse, but this made me crack up so much that I just had to. Thanks for the story!

xamuel4• 2 years ago

No need for the Mac Plus program, you can make these in any text editor. Use a fixed-width font and fill a line with a repeating word eg

WORDWORDWORDWORDWORDWORDWORDWORDWORDWORDWORDWORDWORD

Then copy that and paste it a bunch of times to make it multi-line.

Cross your eyes so that the WORD's overlap (all except the leftmost and rightmost). You now see two cursors instead of one. Position your two cursors anywhere you want and then insert a space in order to make the corresponding WORD (or ORDW or RDWO or ORDW) sink into the screen. (Or rise if you parallel-view.)

We used to do this in the computer labs back in 6th grade.

nayuki• 2 years ago

I discovered this trick independently about a decade ago, to use cross-eyed viewing to easily spot differences between two similar images. Like you said, the parts that mismatch appear to shimmer and be unstable, making them obvious.

However, I feel eye strain from doing it, so I prefer other methods. 99% of the time, I do https://en.wikipedia.org/wiki/Blink_comparator instead, just switching between two images with zero flicker and zero displacement offset. Also with both eyes, it's easier to spot certain kinds of subtle differences like color shifts, JPEG-like compression artifacts, tiny differences in antialiased renderings, etc.

One benefit of the cross-eyed method, though, is that you can difference videos. But the use case for that is rarer than differencing images.

jeffhuys7• 2 years ago

To reduce eye strain, don’t cross your eyes, but relax them (so, the other way). Instantly clear and snaps together as if magnetic.

tartoran2• 2 years ago

The problem I have with this is that instead of the images completely overlapping they overlap a section in the middle. I can't get both images to completely overlap and am getting some eye strain from trying to force them.

claiir2• 2 years ago

This is called “divergence” [1] and is less straining on your eyes than crossing them (“convergence” [2]) while being equally as effective spotting differences, even on video. It’s also what your eyes naturally do when you watch stereoscopic 3D with tinted glasses—the stereoscopic images are pulled out (divergence) not pushed in (convergence/cross-eyed). I’ve been doing this since I childhood. If you get good at it, you can watch side-by-side 3D videos in 3D with just your naked eye (e.g. VR). I believe there’s a reddit covering the more prurient variety of that!

[1] https://en.wikipedia.org/wiki/Vergence#Divergence

[2] https://en.wikipedia.org/wiki/Vergence#Convergence

prmph• 2 years ago

A simple trick to doing this, in case it's not clear how to do it, is to try focusing on an imaginary point behind the screen as you look at the images. You will see a third image between the two start to come into focus. Now relax your eyes and look at that image. Simple, and quite a bit more relaxing than crossing your eyes.

The only disadvantage to this method is that it seems there is a limit to how wide the middle image can be, i.e., the original images may not completely overlap.

If you do want to cross your eyes but do not know how to do it, do the opposite of the above: try to focus on an imaginary point closer to you than the screen as you look at the images. This method is far more taxing on the eyes though.

gnclmorais• 2 years ago

By ready your comment, I just realised that this is what I’m doing instinctively, instead of crossing my eyes :o

NortySpock• 2 years ago

I'll second the blink comparator method as a simple diff checker, or when comparing two chunks of code that are structured exactly the same way but somehow behave differently. (e.g. "what's the difference between these two functions" or "how is this yaml block different from that yaml block"?)

Line them up as two tabs in the editor, flip very rapidly between the two repeatedly, and usually the difference is apparent in 5-6 flips.

biot• 2 years ago

Fun fact: it's a different device, but the principle is the same as the device used in the documentary Tim's Vermeer. It results in the images overlapping between your left and right eye and you simply paint until the difference goes away.

Sharlin• 2 years ago

A blink comparator would be a much better GUI tool for comparing photos (for example original vs. post-processed) than the standard "left half-right half" with a movable divider. Alas, it’s rarely used (eg. Lightroom’s compare view doesn’t have one).

anarticle• 2 years ago

Incredible! This technique is also used for the 3d visualization of protein structures, it was called "cross viewing": https://imgur.com/cross-views-are-commonly-used-to-view-prot...

You cross your eyes to get the two images to line up, hold it there and then try to adjust the focus of your eyes. It's a neat skill to have.

meatmanek• 2 years ago

I found the toolbars and stuff around the edge of the image made it difficult for me to lock onto the crossview image in your example; surrounding it with more blank background makes it easier for me: https://imgur.com/a/NizzRgo

dogman1050• 2 years ago

The stars puzzle helped me find a speck of dirt on my phone screen.

dylan6042• 2 years ago

The funny thing about the stars image is this is a common way to find asteroids, comets. It's not limited to just those. Only instead of a bunch of cross eyed astronomers, they overlay and align the images and do subtraction/difference filtering to see what's left. For comets/asteroids, the dot of interest will move between frames. Even just playing back the aligned images as a timelapse can reveal motion.

dredmorbius3• 2 years ago

Also handy for identifying dead pixels!

norswap• 2 years ago

Wow that's interesting — trying to cross my eyes produces hellish jitter.

I suspect it's because my left eye is slighty lazy.

But I was able to superimpose the right cat picture onto the left one (it's a lot harder for the more complex sky resort picture). It's pretty eerie, the right picture just slides right up the left one (I did need to figure out the right distance for it).

It doesn't help me pick out the differences though, I mostly only see the right picture, and if try to focus my left eye, the right picture slides out. Still, intersting.

xkcd-sucks• 2 years ago

Autostereogramming it doesn't help me lol

If it's perfect, the overlapping regions just merge in color, i.e. the cat's paw becomes off-white. If it's not perfect, I still have to attend to which parts are popping in and out. In both cases I still have to compare the merged view to the left and right hand sides.

Although it is very nice for illustrating each eye's contributions to the merged view. Just not an attention-saver.

evan_• 2 years ago

I use this technique to get web layouts pixel-perfect with the mockup, just put both windows next to one another and superimpose them with your eyes. Works great. There are tools that do this by overlaying an image with 50% alpha but it doesn't work as well.

Last year when there was a bunch of fuss about Kate Middleton not having made any public appearances there was a minor flap where people claimed that a photo she'd released was just an edit of an earlier photo.

There was a tweet presenting two photos, one old and one purporting to be new, where she was holding strikingly similar poses. The claim was that the new one was just an edit of the older one. I used this technique and immediately the minor differences stuck out like a sore thumb- her hand was rotated more in one, her hair was laid differently, etc.

klik99• 2 years ago

I picked this up during the magic eye craze of the 90s, and I will never not find it hilarious how people get shocked at my ability to find the differences. I always share the skill too, it’s one of those things people find impossible until they get it and it’s easy.

twolf910616• 2 years ago

dang it i just did this on a zoom meeting. hopefully no one saw me trying to cross my eyes

TheRealPomax• 2 years ago

This is how I help my family when they're stuck on "spot the difference" steam games. It also takes literally any fun out of them, the actual game has to come from not (just) spotting differences, because that task is trivial.

comonoid2• 2 years ago

I knew some people who used it to compare aerial photos (though generally a special device with mirrors was used).

hk__22• 2 years ago

though generally a special device with mirrors was used

Maybe this: https://en.wikipedia.org/wiki/Blink_comparator

comonoid2• 2 years ago

No, a modification of this: https://en.wikipedia.org/wiki/Stereoscope

7bit• 2 years ago

I've done this on these game machines 30 years ago when I was 10. I'm baffled that there are still people who have to figure this out.

timthorn• 2 years ago

This is effectively how Pluto was discovered (not cross-eyed, but with a tool to help): https://airandspace.si.edu/stories/editorial/finding-pluto-b...

f0e4c2f7• 2 years ago

Front page of HN. Funny to imagine thousands of people sitting in the office crossing their eyes at their computer screen right now.

Fnoord2• 2 years ago

All it did was hurt my eyes. I'll opt out of playing, superpower be damned.

haswell2• 2 years ago

I think the key is not "going cross-eyed" as much as it is relaxing your focus until the images merge. If you intentionally cross your eyes, it hurts. If you de-focus/relax your eyes until the images merge, it doesn't hurt.

llm_trw• 2 years ago

I've used this to quickly read through a few hundred page documents given to us only as a scanned pdf which was too low quality to run ocr (at the time) on. The sleazy counter party was very upset when I came back with notes on them not adding the changes we asked for on the drafts they sent back within minutes of them sending them back.

layer83• 2 years ago

I can’t parse your second sentence.

whatshisface3• 2 years ago

Uncross your eyes! :-)

(They're saying that the person who send the contract was trying to trick them, and that they were upset when the trick was caught.)

fragmede• 2 years ago

a counterparty is the other person you're signing a contract with who sometimes lies to you and says they changed things when they didn't

zupa-hu• 2 years ago

Oh wow you can also use this for contract diffing when signing in person!

jogu2• 2 years ago

I remember doing this as a child on our TV that had a picture-in-picture setting. I would set the same channel twice and cross my eyes pretending that it was 3d TV.

dylan6042• 2 years ago

How does that work when the two images are different sizes and overlapping? Did your PiP mode have a split screen option? The ones I've seen only allowed moving where the insert was placed (which corner), but it was always a PiP and never a split screen.

jogu2• 2 years ago

Yes, it had a split screen option where the two images were the same size and side by side. Can't recall what kind of TV it was... perhaps a Sony?

foobarian• 2 years ago

It's a sailboat!

kayge4• 2 years ago

Hah, Kevin Smith caught some flak for that one:

" Someone called out Kevin Smith for this on one of his podcasts. According to Smith, on the day of filming, he asked if the picture really was a sailboat, and the prop master said no. When Smith started questioning this, the prop master said that a) it flashes on the screen too quickly for anyone in the theatre to notice, and b) VHS was too low-resolution for people to freeze-frame it to try it at home. So Smith let it slide.

Smith summed up, "Now, thanks to Blu-Ray, I get people pointing this out to me all the time!" "

https://www.reddit.com/r/MovieDetails/comments/9lf52b/in_the...

j3s• 2 years ago

all i managed to do was make myself very dizzy

intalentive• 2 years ago

Validates a claim in the predictive processing paradigm. The diff between actual and expected is what matters to error correction. That's where all the relevant information is.

valbaca• 2 years ago

Learned this at a young age with the Highlights magazines at the dentist.

freecodyx• 2 years ago

I used to play this game with a friend when we were at the pub, once we start struggling spotting the differences we know we’re drunk

alfiedotwtf• 2 years ago

This is also how I used to do Magic Eye images when I was a kid. Although the stereoscopic image was inverted on the z axis, it was a lot easier than to cross eyes by looking further out into the distance

unkulunkulu2• 2 years ago

Hah, old trick, I read pull requests this way for years

throw7• 2 years ago

I always feel like I'll permanently see cross eyed if I keep doing that. It doesn't help that I was accidentally hit in the head by my double's partner racket in tennis and spent like a minute or two walking around seeing double. Not fun.

belowm2• 2 years ago

After a short period of training, I got to the point where I can see the third image which I can focus on. However, the differences are very subtile and don't stick out at all :/

drdo• 2 years ago

Try the second test image (the one labelled "Hard", with the snow). That one was far easier for me than the first (the cat one).

belowm2• 2 years ago

Indeed, that did the trick. Thanks!

breadsniffer• 2 years ago

Wow. That’s insane! With the trick I can somehow solve them all!

error404x• 2 years ago

I tried crossing my eyes, but it’s not working for me; I keep seeing things blurry. Maybe I’m doing it wrong. However, I solved the first two puzzles. For the last one, I just guessed randomly. My guess wasn’t exactly correct, but it was close, just a little distance away.

bootwoot• 2 years ago

One thing I noticed: because you're tricking your eyes into thinking they're observing at a different distance, your brain doesn't seem to correctly account for head tilt (my theory of the diagnosis). Anyway, I think you're head must be exactly level with the image or you'll get double-vision/blur

sdwvit• 2 years ago

It’s way trickier if you have astigmatism

evandrofisico• 2 years ago

Come on, I've been doing this since I was like 4 years old, this can't be news for anyone, Am i right???

jeffhuys7• 2 years ago

Yes, I didn’t think people would be so amazed by it either. Like it’s mind-blowing that this works or has been thought of. But we first did it once as well, some people just discover it late in life I guess (or not at all).

manishfoodtechs• 2 years ago

I can overlap. But still need to match overlap with anyone.anyway interesting

soperj2• 2 years ago

Any recommendations for when you can't get the images to quite overlap? I feel like I can get 75% of the way there, but then they start going the other direction. I can do magic eye easily.

kayge4• 2 years ago

Use your browser to zoom out and make the images slightly smaller

soperj2• 2 years ago

this made all the difference in the world.

jasperry• 2 years ago

Claims have been made (outside the medical mainstream) that regularly practicing crossing your eyes helps stave off presbyopia. One does get better at seeing stereograms with practice, so it seems like it at least improves some type of muscle control.

svilen_dobrev2• 2 years ago

uh dunno.

25y ago, i was working behind a 30" tube monitor (a ~35kg hog), with 1 inch thick frontglass.. and one day, one of my eyes started to focus on the (closer)outside of the glass, the other on the (farther)inside of the glass. Could not shake that with closing/blinking. Worse, later, when i got into the car, the closer eye focused on the windshield - instead on the landscape ahead.

Took 1 week of everyday 1-2 hours staring far away at the ocean, to revive. AND removal of the monitor :/

jredwards• 2 years ago

Okay, but my eyes hurt now.

nullbyte• 2 years ago

My Piano teacher used to have this book on her coffee table with images like this. You could blur and cross your eyes, and the image would combine to become 3D.

But I never knew this technique could be used to spot the difference between images. Very cool discovery!

ayeeyeiiieee• 2 years ago

ITT: everyone telling us their stories about how great they are at stereograms. We get it, you're all super special.

rererereferred• 2 years ago

This is a game mechanic in one of the trials in Ace Attorney Chronicles.

woah• 2 years ago

Do people not know about this?

kiwiguy1• 2 years ago

This is the coolest thing I have seen on here!!

cyberax• 2 years ago

This trick had been used in practice to detect fake banknotes and coins, with a device like a two-sided periscope. It allowed a bank worker to put a real coin on one side and the tested sample on the other, so that any differences can be immediately apparent.

iforgotpassword2• 2 years ago

We got a magic eye book when I was maybe 6 - some time early elementary school. After learning how to do it, and also trying it by crossing my eyes to see an "inverted" image, I started doing it whenever I saw some repeating pattern IRL. It was most interesting when it was slightly uneven, for example a fence with sloppily applied vertical planks. Doing the magic eye would make it seem like some of them are closer to you than others. Eventually I tried the same on those "spot the difference" games since well it seemed kinda obvious to try, and I was blown away that it accidentally gave me that "superpower". I think that was pretty smart for a 6yo. Has only gone downhill ever since. ;-)

xamuel4• 2 years ago

I wrote a paper about doing this using human eyes as the "repeating pattern" (either someone else's, or your own in a mirror): https://philpapers.org/archive/ALEDSK.pdf ...You can use this trick to make boring meetings or conversations mildly more amusing (but be careful not to look like a clown crossing your eyes).

If you're an expert at this, you can even do it to your own hands. Hold both hands in front of you but with one of them palm-away and one of them palm-toward you, so that they have the same shape, then cross- or parallel-view them to get an illusionary middle third hand. Walk around while focusing on the third hand and it's a seriously trippy effect.

Another "super power" application similar to OP: the ability to confirm whether or not two distant digital clocks' seconds-digits are perfectly in sync. Since they're distant, it takes time to shift one's gaze from one to the other, making it hard to confirm whether they're in sync. But cross your eyes so as to reduce the distance, and voila.

Yet another application: quickly assume the same head-tilt angle as your conversation partner. Suppose they tilt their head to the left by N degrees and you want to tilt yours the same way, how can you be sure you have the exact correct tilt? Easy: parallel-view their eyes (as described in the aforementioned paper). You will HAVE to tilt your head the same as them in order to see their "third eye" (and once you've locked on to their third eye, you can effortlessly adjust your head tilt as they do by using their third eye as the necessary guide)

mensetmanusman• 2 years ago

Peak HN.

Stereogramming your colleagues eyes during boring meetings.

Edit: I accidentally did something similar by imaging the crease on an N95 mask as a smile near their nose. It made them look like ducks and I had to bite my tongue so hard to not laugh. I could not unsee it.

BenjiWiebe5• 2 years ago

If you're distant enough / the people are sitting close enough, you can stereogram two people's faces together. You usually only get fleeting moments of crispness when their heads are aligned correctly though.

makeworld• 2 years ago

Wow I feel like I've never seen anyone talk about this. Doing it with fences can feel pretty magical, like the object is more "real" than other things.

BenjiWiebe5• 2 years ago

Or the side of a shopping cart.

satvikpendem5• 2 years ago

Now try it with various colors, some people can see "impossible" colors [0].

[0] https://preview.redd.it/yaiyf2bi9aa31.png?width=640&auto=web...

bluSCALE4• 2 years ago

Neat, the colors only blade when perfectly aligned.

dclowd9901• 2 years ago

Yep, this is exactly what came to mind with this "newly unlocked superpower".

I wonder if OP is aware they made a joke about the inability to use this superpower to identify a sailboat in a 90s indie movie.

tonyarkles• 2 years ago

It’s a schooner!

riffraff• 2 years ago

I have never been able to see stereograms (I think because I have an eye which is far "stronger" than the other) and that movie made me feel seen.

effingwewt• 2 years ago

Ethan Suplee is a personal hero of mine. I've been watching him in movies since clerks, and felt bad as I saw him continue to get bigger. When he started his transformation some gym bros posted it to some forums we inhabit. He didn't want to be all public about it since he'd yoyo'd before, but we cheered him on online. When I saw he'd gone public I was so happy for him. His pic now hangs in my home gym with Arnold and Ronnie.

charlieyu1• 2 years ago

I can never do it. Always find it amusing when another kid knows how to do it.

Shocka1• 2 years ago

When I read about Gauss basically inventing Arithmetic Progression at seven years old it gives me similar vibes. What led him to see a different way in adding the numbers 1 to 100? Surely he could have visualized it on his own in an abstract manner, but I tend to wonder if he had a similar enlightening experience like yours.

brailsafe• 2 years ago

Damn, it works exactly that well.

seanssel• 2 years ago

I’ve tried this in the past without luck, but suddenly I can do it now after reading about the subtle “shimmer” effect. Very cool!

svilen_dobrev2• 2 years ago

half-off-topic..

i have ~1 diopter shortsightness. Was less before, slowly going up. So screens are getting blurrier. Have glasses but still try avoid using them.

If i put the (flat edged) TV remote control at about 10cm from my face so it horizontally shadows lower half of both eyes, i see perfectly (without any glasses).

go figure..

HaZeust2• 2 years ago

It works for me like every tenth time I cross my eyes to look at a "spot the difference" picture. I don't know how it works for people instantly.

lxe2• 2 years ago

Instead of crossing your eyes and attempting to focus, what can really help relax your ocular muscles is to do the opposite: look "past" the images into the distance until the images overlap.

adamc2• 2 years ago

I couldn't do the cross-eyed thing, but it took me maybe 20 seconds to spot the difference just by looking at sections of the images. But I'm not sure that would have worked had the missing bean been buried in the denser part of the photo.

AlexandrB• 2 years ago

Some repeating tile patterns like stripes will cause my eyes to do this automatically and it's really weird and annoying because everything else gets blurry. Fun trick though.

StevenNunez• 2 years ago

Jokes on you, my eyes don't work together so I can only see out of one at a time!

ibeff• 2 years ago

There's dozens of us!

mewpmewp25• 2 years ago

Jokes on me - because I learned that today that this is not normal. Now I wonder what other people see...

claiir2• 2 years ago

An alternative technique called “divergence” [1] (pulling your eyes apart) is significantly less straining on your eyes than crossing them (“convergence” [2]) while being equally as effective spotting differences, even on video. It’s also what your eyes naturally do when you watch stereoscopic 3D with tinted glasses—the stereoscopic images are pulled out (divergence) not pushed in (convergence/cross-eyed). I’ve been doing this since I childhood. If you get good at it, you can watch side-by-side 3D videos in 3D with just your naked eye (e.g. VR)! I believe there’s a reddit covering the more prurient variety of that.

[1] https://en.wikipedia.org/wiki/Vergence#Divergence

[2] https://en.wikipedia.org/wiki/Vergence#Convergence

iamjackg2• 2 years ago

This is what I do, the only issue is that I don't have nearly as much "range" with divergence as I do with convergence, so I have to make the pictures as small as possible when using it to line up two images (as opposed to autostereograms, which usually have a much smaller divergence offset).

sirobg3• 2 years ago

Do you have a training method for divergence?

Similar to the finger moving closer and closer to the upper nose technique, for convergence.

Pxtl3• 2 years ago

It's a little more abstract since you don't have handy moving-reference-object like your finger, but: Place the picture in front of something deep, like a long hallway. Look off at something in the distance behind the picture, like the end of the hallway. Notice how the edge of the picture is a double image. Focus on gradually resolving the edge of the picture down from double-image to single-image, and then do the reverse by looking down the hallway again and seeing the picture go back into double-vision. Just keep practicing that until you get the feel for controlling your depth perception and then try holding the same depth of the hallway while you turn your gaze to the picture and try the same action with your eyes.

blipvert• 2 years ago

“Impossible mode” was the easiest for me - took a few seconds. Probably due to the aspect ratio and the size of the images on my phone screen.

mannykannot• 2 years ago

This did not work for me. I was able to invoke a middle image, but there was no shimmering. After I found the difference the old-fashioned way, I realized that the middle image showed the distinguishing feature as it is on my non-dominant side.

nixpulvis• 2 years ago

I can produce the third image by crossing my eyes, but one eye dominates and all I see is a cat with three stripes on its head. :(

bluedino2• 2 years ago

I have been doing this forever, if you get the high score over a certain threshold you can get a free game (400,000?)

I would usually get accused of memorizing all the pictures.

You will get bored or a headache before you stop getting free games using this technique.

You can get stifled by the older machines with faded CRT screens. The newer LCD (that's how old these games are...) are usually better to play on.

on_the_train• 2 years ago

The superpower being writing clickbait titles for trivial posts

tarunkotia• 2 years ago

Image worked but when I tried with text it did not work. Is there some trick to it?

marnett• 2 years ago

Woah that is amazing how quickly I was able to apply this.

So cool!

dathmar• 2 years ago

I was hoping to get a new superpower today, but when I was young I was cross eyed. I got this corrected through surgery and can no longer cross my eyes.

CrimsonCape• 2 years ago

I have a true vision-based super power.

my vision is so bad with nearsightedness that when I take corrective lenses off, I can focus on an ipad mini screen within 10" of my face and perceptually it is the same as focusing on a distant movie theater screen. No straining, eyes totally relaxed.

With the lights off, it's better than being in a theater. I tried an ipad pro in the Apple store and it felt like I had my own personal unfairly huge IMAX screen.

computerdork• 2 years ago

I have really bad vision too (my prescription is left: -8.00, right: -7.50). Tried this out, and yeah, really works! And realized, you need the best resolution screen possible, because you can see every detail. Not sure how much I'll use this is the future, but good to know it's always an option!

boxed• 2 years ago

Natures own VR goggles.

dsubburam• 2 years ago

Unlike when focusing on a movie screen, your eyes have to turn inward to direct the pupils to converge at the physically near iPad. This can cause muscular eye strain (it does for me).

You can get clever and order a prismatic prescription that bends light out, so your eyes don't have to turn inward. I tried it too, but it gave me nausea.

kevinsync• 2 years ago

I've got -7.5 myopia/nearsightedness in both eyes, with astigmatism. As a result, my eyes can easily go out of focus to do Magic Eye or this type of thing. The bonus superpower is, if I take my contacts out and get really close up on something, it's like I'm looking through a microscope; if I happen to have glasses on, sometimes I can also catch the light and focus in just the right way to further magnify what I'm seeing already zoomed in. In those instances I see whatever's reflecting through the glasses, so mostly eyelashes and skin/pores, but it's fascinating nonetheless. Can't see a damn thing beyond the tip of my nose without corrective lenses though LOL

drumttocs8• 2 years ago

Same vision, and I found it hard to do at first- but super cool when the image appeared crystal clear!

uoaei• 2 years ago

I appreciate the sentiment but "overlay the images by crossing your eyes" receiving that kind of incredulous reaction is really funny and kind of sad for me. I hope it's just amateur editorializing.

hyperthesis• 2 years ago

A parallel processor is you!

hn_throwaway_99• 2 years ago

There are some great examples and detailed explanations IMO of this general phenomenon in the book "How the Mind Works" by Stephen Pinker. It essentially discusses how your brain is doing statistical work to build the 3D model from these 2 stereoscopic images.

null0pointer• 2 years ago

You can use this same technique to view glasses-less 3D (stereoscopic) images. It's also fairly easy to create your own. Take two photos but offset the camera lens by approximately eye-width. Open the image editor of your choice and place the images side-by-side. View the composite image cross-eyed and you are now viewing a 3D scene.

Also worth noting there are 2 versions of this kind of cross-eyed focus depending on whether your eyes are focusing on a point in front of or behind the actual image. This determines which side the left and right eye images should go on in the composite. I find it easier to focus on a point in front of the images but IME most examples online are for focusing on a point behind the image.

thwg• 2 years ago

Please stop using that RSS icon on your "Subscribe" button if you don't intend to provide an RSS feed.

sirobg3• 2 years ago

This is incredible! Works unbelievably well. Thanks for sharing!

kazinator• 2 years ago

I found it almost instantly, which was by dumb luck.

But in the following few moments, seeing two nearly identical photos side by side soon made me think of stereograms, since I'm into them, and have shot a few in my lifetime.

I then used my eyes to overlap the images.

In binocular overlapped view, the difference loudly draws attention to itself, because it flickers between the two eyes.

It's almost as if there were a blinking LED saying "here it is!"

smusamashah4• 2 years ago

For anyone who wants to learn this, try this way using your finger as a helper.

Put the images in front of your eyes.

Bring your finger between your face and the image at almost middle of the distance.

Now look at your finger.

Move your finger back and forth and notice the background (where your picture is)

While doing this, notice that at a particular distance, the images in background will perfectly overlap each other.

That's your moment.

Pull out your finger and look at that image.

It worked on everyone I have tried to teach. You may always need help of your finger or a tip of a pencil or whatever. But it's lot easier to get those images to merge this way.

skeaker• 2 years ago

My eyes seem to immediately refocus as soon as my finger moves away no matter how many times I try this. Before I move my finger away, everything in my peripheral vision is too blurry to be useful.

nhumrich• 2 years ago

Does this only work on desktop? I am trying this on mobile and the images never overlap. Wondering if maybe my viewport is too smal

rahimnathwani2• 2 years ago

I've always been able to merge pictures by focusing into the distance, and I thought that's how everyone did it. So I found confusing all the talk of crossing eyes. I tried your instructions and, within 30 seconds, was able to see the cat image by crossing my eyes.

The cross eyed method seems more amenable to different image sizes. With my regular method, I can't merge images if they're too large (unless I step back).

dusted• 2 years ago

I that not the entire point with those "find the difference" pictures? To teach kids how to do just this ?

sneak• 2 years ago

I was able to do it for the first time after reading this webpage with the technique, cool!

mjal• 2 years ago

Nice to see someone discover this! I've always been partial to spot the differences and crossview images - I am able to cross each eye independently of one another, which makes overlapping these sorts of images very easy. For example, I could cross my right eye, while my left stays perfectly still. This causes instant double vision, and relaxing how crossed the eye is lets me line the images up very quickly. It's fun to do in places with a repetitive wall texture, too - seeing something in real life while adding a faux 3D effect on top of it is kind of trippy. Probably my most useless skill, but a fun one regardless.

theginger• 2 years ago

Is the technique to this exactly the same as the technique to view a 3d stereogram image?

I was able to get a 3rd image to be clearly visible in the middle doing this, on the 2nd image I could definitely seem some spots appear that lead me straight to 3 of them but didn't work for me on the other 2 images.

Pxtl3• 2 years ago

The left-right full-image stereograms... but those are less common than the pattern-based "magic eye" stereograms. Those are the reverse of this - in the linked image and the left-right full-image stereograms, they're done by crossing your eyes to a point closer to your eyes than the original image.

The pattern-based "magic eye" stereograms are done by looking through the image to focus on a point deeper into the screen further from your eyes.

The latter I think are less painful because they use the more natural depth-perception distances of your eyes instead of using what feels like more unnatural positions, but that might be my bias because I'm a bit farsighted. Maybe they're just more common because they're visually inscrutable at first and so you get the "reveal" of the 3D contour from a single large image instead of two already-visible small ones.

amingilani2• 2 years ago

I'm frequently surprised by the amount of seemingly ordinary skills I picked up as a bored child that other people didn't. This was an obvious way to solve those "spot the difference" pictures in magazines.

I wonder what skills other people picked up that I didn't.

Some recent example of things I shared:

+ When your belt buckle hangs a little loosely on the front of your pants. You can hook the buckle's prong onto the front button of your pants and it'll stay put. So many people are excited to learn this.

+ Putting a jacket or any open-front garment on quickly. I saw someone struggling to maneuver their second arm in a tight jacket behind their back. I explained that if they hold their jacket out in front of them, put their hands in the arm holds, and slide their arm in further as they swing it around their body they'll get it on in a moment. It's also more stylish. They were so surprised.

xamuel4• 2 years ago

Ear rumbling: https://www.reddit.com/r/earrumblersassemble/

Eye shaking: https://old.reddit.com/r/Eyeshakers/

Some of us are born with small frenula of the tongue (or we undergo tongue-tie surgery as kids) and can thus perform Khecari mudra without the traditional self-mutilation used by yoga-masters. https://en.wikipedia.org/wiki/Khecar%C4%AB_mudr%C4%81 This can be useful for cleaning tonsil stones or post-nasal drip, but of course you must do so discretely since people would consider that absolutely disgusting

If you want to read out loud for long stretches of time and you hate taking breaks to catch your breath: you can read out loud while inhaling too! (It feels and sounds super weird though so this isn't very useful in practice.)

And here's a party trick related to OP's super power. Pick a distant object and cross your eyes so as to see it double, preferably with the two doubles distant from each other (i.e., cross your eyes significantly). Then, alternately switch between staring at the left double, and the right double. If you do it right, it will look like your eyes are moving in a bizarre alien way.

emmelaich2• 2 years ago

Here's mine. Look at a patch of grass and ask someone to spot the ant or bug.

It's quite difficult.

But, if you let your eyes go out of focus, the ground will suddenly become alive with movement of all sorts of ants bugs and creepy-crawlies.

kdmtctl• 2 years ago

When your belt buckle hangs a little loosely on the front of your pants. You can hook the buckle's prong onto the front button of your pants and it'll stay put. So many people are excited to learn this.

Yep. And there is a special vertical prong keeper tab on some trousers for exactly this purpose.

TeMPOraL2• 2 years ago

I'm frequently surprised by the amount of seemingly ordinary skills I picked up as a bored child that other people didn't. This was an obvious way to solve those "spot the difference" pictures in magazines.

Conversely, I'm amazed by the amount of things I discover as an adult are not common experiences or skills for people, despite being considered as such. This includes, for example, having an inner voice (which I do), or ability to visualize things in your head (which I don't).

Wrt. the latter, when I learned as an adult that some people actually can conjure up images in their mind on demand[0], and conversely that aphantasia is a thing, it took me few more years to connect that back to some early experiences in childhood - being bored out of my mind by some well-known novels that my parents and teachers found particularly engaging. Specifically, the ones rich in descriptions of scenery. They'd say that's the best part, what makes the story rich and immersive, and that's what imagination is for and those books are good for exercising it. Meanwhile, I'd feel ashamed and wonder what the fuck are they talking about, while skimming to find where the descriptions end so I can resume reading from there. Well, it turns out what they said was true for them, but is not true for people like me, who can't visualize to save their life.

Well, except in dreams. Which makes the whole thing even more fascinating.

Some recent example of things I shared:

Interesting. I somehow managed to never learn either, so thanks! Ironically, I realize now I've probably seen people do the jacket swing trick hundreds of times, and yet it never registered in my mind as a distinct technique, much less one that I could learn.

EDIT:

One such skill I didn't pick up until my wife taught me, and that I know many (most?) people don't know, is how to correctly pour liquids out of rectangular containers with off-centre openings. Think a milk box, or 5L jug, or fuel canister. Turns out, you shouldn't flip them to give the liquid the shortest path to destination, but the opposite - have it flow alongside the entire top edge of the container. This gives you steadier flow, and you'll spill less. I still find it counterintuitive, but it works.

[0] - Fun fact: that makes "undressing someone with your eyes" a literal ability for them too.

v-erne• 2 years ago

> Well, it turns out what they said was true for them, but is not true for people like me, who can't visualize to save their life.

I used to be exactly like this - I could not visualize anything. Which was very perplexing for young me - I was astonishingly good at math (winning some country level math competitions even) but could not get past some arbitrary but somehow low level geometry problems. Then it struck me - I could not see the solutions in my head, only on paper, which drastically limited my search space.

But latley after years od doing other thing (including more artsy stuff like drawing) I discovered that I was wrong - its it possible to learn, its just that some people gets this faster and with little effort. For me it was just a other few thousend hours of doing staff that accidentally expanded my visualization ability and then "miracle" happend.

The same was with my supposed tone deafness - guess what, I only believed my self info being tone deaf (real tone deafness is very bery rare). I just was lazy in this departament (in building my ability to perceive tones).

rmellow• 2 years ago

Specifically, the ones rich in descriptions of scenery. (...) skimming to find where the descriptions end so I can resume reading from there.

I've always been good at conjuring images in my mind, but I also skip the drawn out visual descriptions.

I could never enjoy Lord of the Rings due to Tolkien's love of describing trees (of the wooden and familial kinds)

Xerox9213• 2 years ago

My odd claim to fame which is hard to garner praise for is that when I was a kid I always followed a certain pattern when I did something on a left or right foot. I always tried to even it out. So if I pinched my left toes, then I would do my right. But then I would undo that by going right then left. And then I would undo that by undoing the entire thing: right left left right. And the pattern went on:

LRRLRLLRRLLRLRRL…

and so on. It seemed easy enough to remember because you would just undo what you did last.

A few decades later and I learn that’s the Thue Morse word (1) which has many interesting properties like being overlap free. Unfortunately it didn’t give me any kind of advantage when studying combinatorics on words. Just a weird “wait… where have I seen this before?” moment.

[1] https://en.wikipedia.org/wiki/Thue%E2%80%93Morse_sequence

_nivlac_• 2 years ago

I did the exact same thing, due to a feeling of wanting to "even" things out between right and left. Blew my mind that it was a known pattern; after watching this video: https://www.youtube.com/watch?v=prh72BLNjIk&t=549s

I'm always reminded that we are all more alike than we realise :)

aimor• 2 years ago

For when you feel a sneeze coming on:

- Want to sneeze? Look at a bright light.

- Don't want to sneeze? Scratch your ear.

altgeek• 2 years ago

Stereograms have been used in structural biology publications for many decades now. Google 'stereogram structural biology'

tristramb• 2 years ago

I've been using this to do quick source code diffs for years. I started back on the days of printouts.

athom2• 2 years ago

Easily defeated by arranging the images vertically.

Or at least, makes it a LITTLE bit harder.

sota_pop• 2 years ago

Wonderful! with your write-up, I was able to “see”.

pbhjpbhj4• 2 years ago

I've always thought that ability to unfocus the eyes might be related to mental focus. If you have difficulty staying on topic, or a diagnosis of ADD/ADHD or whatever {I'm not equate these} AND find it really hard to do magic eye images... Then please take part in my 'totally scientific study'TM.

pbhjpbhj4• 2 years ago

Upvotes, I agree, I have mental focus issues and can't do magic eye (upvote)

pbhjpbhj4• 2 years ago

Downvotes, I disagree (downvote)

{I should have done an actual survey, sorry; felt cute might delete.}

pbhjpbhj4• 2 years ago

I have mental focus problems, magic eye is easy for me. (downvote)

dalemyers• 2 years ago

I'm amazed that there's so many comments and yet not a single one is pointing out that the coffee bean is missing from the _right_ side of the image. Not the left.

dabber21• 2 years ago

Wait, this is news? that's how I always solved those puzzles, I thought everyone did that

rahimnathwani2• 2 years ago

I find it very easy to overlap images, I think because of the eye exercises I had to do as kid.

I don't recall what these exercises were for, but there were two:

1. Stare at this image of two incomplete cats, and merge them together into a single complete cat: https://www.google.com/search?q=eye+muscle+cat+card

2. This strip of cardboard has a number line on it. Put one end half way down your nose, perpendicular to your face. You will see two lines. Merge them at their furthest point, then merge the next nearest point, repeat. (I think this is called the 'Brock String Exercise', but can't find an image similar to the one I recall.)

luxuryballs• 2 years ago

yep it’s just like those magic eye pictures that were big in the 90s, once you learn how to see those instantly you can do this trick also

hprotagonist• 2 years ago

Good old vdiff: https://catb.org/jargon/html/V/vdiff.html

Visual diff. The operation of finding differences between two files by eyeball search. The term optical diff has also been reported, and is sometimes more specifically used for the act of superimposing two nearly identical printouts on one another and holding them up to a light to spot differences. Though this method is poor for detecting omissions in the ‘rear’ file, it can also be used with printouts of graphics, a claim few if any diff programs can make. See diff.

An interesting variant of the vdiff technique usable by anyone who has sufficient control over the parallax of their eyeballs (e.g. those who can easily view random-dot stereograms), is to hold up two paper printouts and go cross-eyed to superimpose them. This invokes deep, fast, built-in image comparison wetware (the same machinery responsible for depth perception) and differences stand out almost immediately. This technique is good for finding edits in graphical images, or for comparing an image with a compressed version to spot artifacts.

JeremyHerrman• 2 years ago

To really blow peoples' minds use both hands to tap the differences, keeping the left hand for the left image and the right hand for the right image!

From your POV the images are merged so your hands will look like they're tapping a single image, but from the audience's point of view you look like a savant with multi-attention!

leecarraher• 2 years ago

i certainly used this trick back in my college days, prompted by a similar technique for "seeing" 3d stereoscopes on a computer monitor. I feel like i learned it somewhere on Eric Weisstein's Mathworld because the 3d objects viwer app let you split the image into two stereo images. Unfortunately java applets have been banished from the internet landscape.

Balgair• 2 years ago

You can also use this to display 3-D images. You have a stereographic projection of your image (like those kids' view-masters) and then just cross the eyes and look at the middle image. Only since the 2 images are slightly different, you can have the middle image be 3-D. It takes a bit of practice though and causes eye strain (at least for me)

It's not a great way of showing the image, but it'll do in a pinch.

scrozier3• 2 years ago

I spent weeks doing this, looking at stereoscopic (?) images of protein structures, while a grad student in molecular biophysics. I got so that I could see the overlapped images pretty much instantly. But I'm having a hard time getting it now, even on the easy one.

javaskrrt• 2 years ago

okay, this is so cool. thank you for the new superpower!

modzu• 2 years ago

and now my eyes are stuck this way forever

mads_quist• 2 years ago

Fuck it does work...

emh68• 2 years ago

Wow! It really works. The missing bean "pops" out at you. The hardest part is getting your brain to focus on the cross-eyed virtual center image.

grishka• 2 years ago

This whole "just cross your eyes" thing has never worked for me, not once. I've seen these strange patterns printed on the backs of notebooks that supposedly make some sort of 3D effect when you "just cross your eyes". Later, when I saw similar images online, I was able to at least visualize these hidden shapes by opening the image in photoshop, duplicating the layer, setting the copy to "difference" and moving it left or right. The regular texture would eventually disappear and the shape would emerge. It's still a mystery to me what it feels like to view these the intended way though.

titzer2• 2 years ago

Here are some tips;

1. When you cross your eyes, gradually let them return to uncrossed. Try to do it as slow as possible. Along the way, try to line up any structures that you see in the image that are repeated from left/right half.

2. Once you are able to hold a cross-eyed gaze long enough with lined up left/right half, slowly move your eyes between different features near the middle. Your eyes will naturally want to start to focus and match up pieces.

3. Don't be too far or too close to the image; they are usually easily viewed from comfortable distances. If the image is too big, make it smaller. It's usually easier smaller.

4. Initially, when you cross your eyes, or look through the image, it will likely be blurry. This is because your brain naturally associates accomodation and convergence with also changing focus. You'll learn to decouple those things and you will more quickly be able to go from focusing on the 2D image to crossing it without changing focus much.

There's a whole bunch on this site: https://www.magiceye.com/stwkdisp.htm

einpoklum• 2 years ago

1. When you cross your eyes,

So, how exactly is that supposed to work?

I can manage some de-focusing which makes me see 4 images rather than two. Is that part of it? Otherwise, I don't get it.

ndxf• 2 years ago

Doesn't work for me either. I just made myself queasy while trying to cross my eyes for ten minutes haha

mplanchard• 2 years ago

I've also always had a hard time with these. I suspect it's because one of my eyes was slightly lazy when I was a child, so my brain learned to put more importance on the signal from the other eye. When I cross my eyes, the image from the better eye tends to just totally override the other one, so it can be really hard to see these kinds of effects.

davejohnclark• 2 years ago

I have exactly this as well. My optician explained it as my brain would use the information from the lazier eye only if there wasn't any information from the good eye. Just tried the eyes crossed trick on the easy image in the article and the 3rd image in the middle is the right one. If I let them drift apart so there are 4 images I can see the left one and the difference (because I'd already found it), but as soon as I force them to overlap the left signal disappears and I'm only seeing the right image. I've also never managed to do a magic eye or anything, and 3d movies just give me a headache.

fonema• 2 years ago

Same here, but I always imagined that for it to work, I would need to have roughly equal vision in both eyes, which I don't. Everything is blurry with my left eye, and no glasses or lenses have ever helped. I attribute this as the reason.

mickeythug• 2 years ago

Suffering from the same exact plight

r3trohack3r• 2 years ago

I just spent 30 minutes trying to get any of these examples to work before it clicked.

What worked for me: I’m not “crossing my eyes.” Trying to cross my eyes precisely enough to get the two images to overlap was impossible.

Instead I’m starting by crossing my eyes until a third out of focus image starts to appear between the other two images, then I immediately abandon trying to cross my eyes and instead focus on bringing that third image into focus like it’s “floating” in the room at a different point in space than the page its on.

Apparently the circuits in my brain and eyes are good at this. As soon as I can get the “third image” to show up by crossing my eyes, I can “look” at it and my eyes snap perfectly into position.

After about 5 minutes of practicing I can focus on the third image in about a second from the time I begin to cross my eyes.

On the third image, the differences between the two images “shimmer” like a holographic foil on a playing card.

guico• 2 years ago

This is exactly why I read HN

jon309• 2 years ago

This does not work even in the slightest. When I cross my eyes, the image becomes wayyyy too blurry and its hard to keep it in the center for more than a second

tessellated• 2 years ago

That's how I used to help my grandmother when I was a little child. She always used to remark that the last one (5th) was the most difficult to find.

sailfast2• 2 years ago

This whole time it's been a Magic Eye problem? Geeeeez. This would've won me so many random challenges over the years.

y-c-o-m-b• 2 years ago

Well this is interesting. I was able to find the impossible one within 2 seconds without crossing my eyes. The easy one took about 5 seconds, 3 seconds for hard. I've always been hyper-vigilant with patterns (to a fault), so not sure if that's playing into this.

Is that what other folks are experiencing also? I see most comments are trying it with their eyes crossed, but what about without?

EDIT: ok I just watched the video. No eyes crossed. For the balloons one I beat out the girl in the video by 2-3 seconds. For the birds about the same. The skittles one tripped me up, couldn't find it. The other few I found around the same time, the lights at the end I didn't find in time either. It seems I'm quicker when there's not too many colors involved. Still that's spooky.

mmh0000• 2 years ago

There's a video game of this called QuickSpot. Back in 2008, this was one of my favorite games for the Nintendo DS. It trains the ability to spot little differences quickly. Sadly, outside of winning a barely known video game, it's not a super useful skill.

https://en.wikipedia.org/wiki/QuickSpot

ChildOfChaos• 2 years ago

I can't seem to do this, it seems impossible for me to cross my eyes. Hmmm.

lobo_tuerto• 2 years ago

This is exactly the same skill needed to see 3d pictures (aka autostereograms).

s4i• 2 years ago

Almost certainly a lot of the people saying they are ”crossing” their eyes are actually ”uncrossing” their eyes; focusing the eyes straighter than what would normally happen on the surface where the image is laid out.

This is also how the legendary ”Magic Eye” books were supposed to be viewed. Not by crossing the eyes.

Imnimo• 2 years ago

I can get the overlap to lock in, but the simmering effect is weak and difficult to pick out. Probably still faster than exhaustive search, but I don't feel like I'm at superpower level. Maybe my brain favors one eye more than the other? I know I have different glasses prescriptions for each eye.

topspin• 2 years ago

It tried just after waking up, using my phone's screen, and it worked immediately. Not exactly a pleasant thing to do, but it does work as described.

labanimalster• 2 years ago

Learned it from Magic Eye books too! But using it for spot-the-difference is way more practical - saves so much time compared to staring at two pictures. Kind of feels like having X-ray vision for finding differences

abotsis• 2 years ago

I have strabismus and have always been good at these games. I wonder if it helps me for similar reasons? The examples on his page were pretty easy for me, though the universe one took maybe 45 seconds.

dlgeek2• 2 years ago

Funny. I also have strabismus and I've never, ever been able to see those hidden picture games or these things even once.

I never developed stereoscopic depth perception, which I assume is related.

phist_mcgee• 2 years ago

Same here, i've always wondered what other people see. An optometrist once said that I see everything as if viewing a tv screen through my eyes, but having no point of reference it looks normal to me. I am pretty bad at parallel parking though, perhaps that's my lack of 'native' depth perception.

raggles• 2 years ago

yea same boat. I've always wondered what normal depth perception looks like. On the plus side, it is fun to challenge people to wear an eye patch and play table tennis or some other activity and see how bad they are when they haven't developed monocular depth perception cues.

rahulvarshneya• 2 years ago

This is just incredible!

PUSH_AX• 2 years ago

A ton of comments in here saying this is easy/old hat for them.

Well I'll be the one to say this blew my mind. somehow creating the third middle image, being able to relax my eyes and even scan around this composite image actually made me giggle out loud on my laptop, a very rare occurrence. Thank you to the author.

EVa5I7bHFq9mnYK• 2 years ago

Using this trick, I wrote a program for 3d plot visualization in the 80-s. It computed two projections of the plot, as if looked by left and right eye, and printed them side to side on the thermal printer. If you looked hard enough, you can bring the two pictures together and see a 3d picture!

Slow_Hand• 2 years ago

This trick is interesting to me as someone who mixes records. I (and mixers in general) have a lot of different tricks for making mono audio objects in the mix feel stereo or have a sense of width or depth.

Examples include:

1. Delaying the left or right channel by a few ms (Haas effect).

2. De-tuning one of the channels by a few cents

3. Boosting an EQ band on one channel, with a complimentary cut on the opposite channel.

...and many more.

These are usually very subtle changes that our stereoscopic ears have no problem detecting.

In any case, when we need to do some forensic searching for possible differences between two near-identical channels we'll invert the polarity on one channel and then sum them. The resulting delta sticks out like a sore thumb and highlights even then tiniest differences between the files.

So it's fascinating to discover that we can easily do something similar with our eyes to find the differences.

simplicio• 2 years ago

Feel like people who are old enough to remember that 6 week period in the 90's where those Magic Eye 3d Stereogram pictures were everywhere have a big advantage here.

shkkmo• 2 years ago

I cannot do this by crossing my eyes (focusing on a point between you and the image), I have a hard time getting the cross to stay consistent and it never really "locks in" for me. Instead of crossing my eyes, I unfocus them, effectively look through the image. Once I get the repeating part to overlap cleanly, after a second or two, my pupils adjust their focus and the image fades from blurry to clear in a really satisfying way and kind of "locks in" in a way that takes little to no effort to maintain. With a bit of practice, I can even move my eyes around and look at different parts of the two overlayed images without distrupting the effect at all.

I don't know if it's just my brain working differently or if a there is some confusion in the discussion between crossing your eyes and focusing through an item.

JoeOfTexas• 2 years ago

Wife was not impressed. That hit home haha.

codefoster• 2 years ago

I didn't spend the time reading the comments to see if this has been said already, but crossing your eyes works but learning to diverge your eyes is better in some situations. It's easier to learn to cross because you can just look at your nose, and you can bring together two images that are further away by crossing than by diverging. But diverging is the way we are normally (when looking across the room say instead of at a book in front of us) so it's more comfortable.

cal85• 2 years ago

Interesting, what kind of situations does it come in handy?

netman21• 2 years ago

As a kid I learned to see stereograms in 3D by crossing my eyes. Exact same technique. Comes in handy for Mars images today.

dionian• 2 years ago

I've never been able to 'lock' the two images together like this with my eyes focus. That was incredible.

GMoromisato• 2 years ago

As I understand it, Magic Eye stereoscopic images were originally developed by brain scientists studying how we see in 3D (i.e., how the brain processes 2 eye inputs into a 3D image).

There were two competing theories:

1. The brain first does a recognition pass (that's a house, that's a person, etc.) and compares the two eyes to see which objects have moved.

2. The brain compares the two eye inputs first, at the "pixel" level and figures out which pattern of pixels has moved, then afterwards, applies recognition to the resulting 3D image.

Magic Eye would only work if #2 is the correct theory (because in Magic Eye, there is nothing to recognize until AFTER you convert to 3D).

TeMPOraL2• 2 years ago

1. Get a bit closer to the screen so you can see both images clearly.

2. Now, cross your eyes and aim to overlap both images.

3. Draw the rest of the fucking owl.

Seriously. Ever since my physics teacher in high school tried to get the class interested in stereograms, everyone and every article I see talking about it treat "crossing your eyes" as an atomic, trivial step. It isn't. I for one have no first clue how to do it, it's not a distinct operation I know how to perform. Perhaps this is because I am nearsighted and wear glasses.

Still, I wish articles like these focused on explaining how to do the whole cross-eye thing, because once you master that, everything else becomes instantly self-apparent and doesn't need further explanation (I know because I did manage to accidentally cross my eyes once or twice while looking at a stereogram, so I know how the effect looks like).

EDIT: FWIW, I compensate by using another trick for diffing documents with Mark I Eyeball - get them printed on separate pieces of paper, put one on top of the other, and hold in front of you with some bright light behind you (Sun, or your phone's flashlight, will do). Not as good as crossing your eyes, but something I can reliably do.

z3t4• 2 years ago

You can also use this method to watch 3d movies without vr googles.

srinathkrishna• 2 years ago

Wow! That was amazing!

justinl33• 2 years ago

human stereo vision processing has incredibly sophisticated noise filtering capabilities that are still hard to replicate in software. The shimmering effect people report is essentially your visual cortex highlighting areas where the stereo correspondence fails.

calebm• 2 years ago

Super cool. It works for me. I love magic eye stuff.

jrmylow• 2 years ago

The most mind-bending example of the magic eye effect I've found is people using it in videos.

Of course, the internet being what it is, someone made a version of Bad Apple with it: https://www.youtube.com/watch?v=RLuGJGyCS90

rsktaker• 2 years ago

That's amazing! Within 40 seconds I overlapped the two hard mode images and saw 8 shimmering objects set within a clear picture. It took me a little longer (maybe a minute), but the two impossible mode pictures snapped together and I saw a single shimmering star within an otherwise crystal clear photograph!

k2enemy• 2 years ago

You can make the impossible picture (the others too) easier by slightly moving your head back and forth while superimposing the images. The difference will move more than the rest of the image.

tlhunter• 2 years ago

It blows my mind that every human doesn't know this. I figured it out as a child. The easiest way to prevent this is to have one of the two images be slightly tilted. I can rotate my eyes but it's much harder than crossing them.

nneonneo• 2 years ago

For whatever reason, it was far easier to do this on my phone than on my laptop, even after trying to fiddle with various combinations of zooming in/out and adjusting my distance to the screen. In some cases, it can also be easier to do without glasses (if you customarily wear them) as it makes the defocusing easier.

The effect itself is basically similar to the Magic Eye stereograms (https://en.wikipedia.org/wiki/Magic_Eye) which by themselves are pretty neat; your brain can rapidly detect subtle offsets in random patterns to reconstruct depth cues. In the case of “spot the differences”, the shimmering is due to the irreconcilable disparity between left and right images, which manifests visually as a glaringly obvious “unphysical” apparition - e.g. flickering between the left/right images, or appearing to be out-of-plane with the rest of the picture.

efskap• 2 years ago

The specific term for the shimmering mechanism is https://en.wikipedia.org/wiki/Binocular_rivalry

gwd• 2 years ago

What's astounding about this is simply the staggering amount of visual processing your brain is capable of doing in parallel.

cubefox• 2 years ago

Exactly, and it is some form of computing power we normally do not have voluntary access to.

netsharc• 2 years ago

We know the direction a sound comes from due to milliseconds of difference of the soundwave arriving in one eardrum and then the other...

donatj• 2 years ago

As someone with a lazy eye it's kind of hilarious to me that this isn't common knowledge.

nepthar• 2 years ago

I cannot believe this is unknown to so many people that it's news

Ylpertnodi• 2 years ago

I cannot believe (well, I can!) that 10,000 by xkcd is unknown to so many people that it's going to be news to them when they look it up.

TZubiri• 2 years ago

This makes my eyes hurt.

And it's also not really a usefull life or even primitive skill, just a byproduct of our double eyeballs, which are meant for redundancy and depth measuring.

Pass.

(Although it was cool to do it once and see the third image in the middle.)

lazycouchpotato• 2 years ago

Fascinating!

I was able to grab focus for the first image. Found it hard for the second and third image. I focused on the first one and then scrolled down to the second and third - that made it easier for me.

scrapcode• 2 years ago

Great read. Not sure it was worth being stuck cross-eyed for the evening, though.

sans_souse2• 2 years ago

Would AI not be able to crush this game?

gameman144• 2 years ago

`memcmp` would be able to crush this game, but the fun is in doing it as a human!

phyzome• 2 years ago

15 lines of Python would be able to crush this game. But that's not the point.

sans_souse2• 2 years ago

Easy, fellas. . .

ekTHEN• 2 years ago

using the same trick, watch this video: https://www.youtube.com/watch?v=zBa-bCxsZDk

nazgulnarsil• 2 years ago

A bunch of math is like this too.

wexomania• 2 years ago

Back when I studied media and communications, around when the first avatar movie created a hype for 3D movies. Me and a couple of friends decided to try and make a 3D movie for class. We made a custom camera rig out of metal brackets and edited the movies cross eyed since we had no actual way of editing in 3D, worked like a charm, altho, it was really hard to get the 3D right.

astura• 2 years ago

As usual, this doesn't work for me because I don't have stereoscopic vision.

armada651• 2 years ago

Am I weird for almost immediately spotting the missing bean as soon as the image showed up? It certainly would've taken me longer to adjust my eyes for the cross-eyed trick.

Even the impossible one was harder when trying to use the cross-eyed trick than just visually comparing the two by quickly moving my eyes back and forth.

panzi• 2 years ago

I found two differences in the last picture. Turns out the second was dust on my monitor. XD

qwertox• 2 years ago

I've used this method as a diff tool for years. Be it code or product comparison, like CPU specs, or these "spot the difference" images, crossing the eyes can be really useful.

mcarmichael• 2 years ago

Add some trigonometry, and this superpower has historical military applications:

  https://en.wikipedia.org/wiki/Stereoscopic_rangefinder
  https://www.youtube.com/watch?v=cbXyAzGtIX8

gcanyon2• 2 years ago

I am so remarkably one-eye dominant (my left) that the first image just looks like the right cat to me about 98% of the time. Every once in a bit I'll see the flicker, but even then it's faint and hard to notice.

devmor• 2 years ago

I've been doing this for years and always considered it my secret little hack!

iDon• 2 years ago

I use this for quick comparison of minor differences in code / data (e.g. tables, DNA sequences). Variations in indentation are highlighted also, by standing out of the plane.

It's good to hear reports of successful viewing. I've got a 3d / stereogram photo gallery app on the back burner; sounds like a reasonable number of people would be able to view it. There are plenty of guides on how to learn this; some are linked here https://www.reddit.com/r/CrossView/wiki/index/. You-tube used to have support for this; there are still videos tagged yt3d - just regular videos now, not interlaced.

fudged71• 2 years ago

I wonder if this would be a legitimate form of code diff visualization with VR glasses, just show the A and B for each eye

ksec• 2 years ago

Am I the only one who cant do that? Or does me having aphantasia has anything to do with it?

mattigames• 2 years ago

It would be pretty weird for aphantasia to have something to do with it, it's pretty much using the same technique one can use for cheap 3D effect with 2 videos from cameras slightly apart, it has everything to do with our bifocal abilities and not much else as far as I can tell.

Fr0styMatt88• 2 years ago

I taught myself how to free-view stereo side-by-side images on my phone but after I did so I found that I would get strong stereo impressions involuntarily just looking at certain repeating patterns in normal circumstances like watching TV with side-by-side images or when looking at patterned wallpaper.

My visual system is pretty weird in general so I don’t know how common an experience this is with others. It’s not bothersome at all because I know what it is but it was a little startling the first few times.

lutusp• 2 years ago

Many decades ago, during my time as a NASA Space Shuttle engineer, a co-worker couldn't locate a rogue unbalanced parenthesis in a complex program listing, in the days when computers, instead of identifying a particular syntax error, would print lame error messages like "Something went wrong." Worse, we wrote programs by punching 80-column cards -- no syntax highlighting, no color monitors.

My co-worker printed two paper listings, one with the error, one without, and asked me to count parentheses as he was doing, over a dozen pages. But because I knew this "superpower" trick, I laid out pairs of pages and crossed my eyes. A few seconds later I found and circled the error.

"Ta-daa!" I said. He never forgave me.

144• 2 years ago

Yes that top reddit comment is right. Years ago those magic eye pictures came out and at first I struggled to see the 3d pictures. Eventually it became trivial. Then somewhere I noticed it worked really well for those spot the difference puzzles. They often come on kids menus at some restaurants. I could spot all ten differences in seconds and my kids would be amazed. I finally tried to teach them but they found it hard to do. But ya in reality what this girl did was super easy and not challenging in the slightest. When you do it and cross your eyes inwards you cross your eyes until the pictures line up in the middle. The majority of the picture will be clear but any spots that are different will seem blurry. The trick is just not focus on anything in particular and just cross images until they clear up. Then make note of where it seems blurry. Cool trick but definitely ruined spot the difference puzzles for me.

zoklet-enjoyer• 2 years ago

It's a sailboat

matt3210• 2 years ago

Corporate needs you to find the differences between theses two images

mukunda_johnson• 2 years ago

Those kinds of puzzles are part of the CCAT test (annoying test for "cognitive aptitude") and I used this trick.

ashleyn• 2 years ago

my grandmother used to tell me if i went cross-eyed too much, they'd get stuck like that. it took me until a google search at age 15 to see that was an old wives' tale...

rashidae2• 2 years ago

Wow, I didn’t know I could do that!!

I’m not sure how this new learned trick, can apply to other stuff… but I’m happy I tried it and it did amazed me haha thanks for the share dude!

rashidae2• 2 years ago

1 hour from my tests, my eyes still hurt though!!!

ribs• 2 years ago

What has happened to me? How am I able to create a combined image and have it be -stable-? This totally works. I’ve been mutated.

User23• 2 years ago

I instantly knew as soon as I saw the image. It's the Magic Eye trick. The same one you use to view stereoscopic images. The differences will just flicker.

nomilk• 2 years ago

Amazing! Tiny bit of feedback, it might help to add to the article that there's 1 difference to spot in impossible mode (the other two difficulties say there's 3 and 8 diffs respectively, which is useful to know when attempting).

ompogUe• 2 years ago

Semester 1 when getting a BFA in painting the prof told us to do this to help tighten composition

econ2• 2 years ago

Open the image in the Gimp. Duplicate layer adjust opacity then drag it sideways until they line up. Toggle layer visibility.....

Wait, why isn't there a service for this? Or is there?

pontifier• 2 years ago

Set layer mode to "difference" and everything that overlaps exactly fades to black.

On a stereo image sliding the top image is very interesting as areas at different distances fade at different positions.

Here is an example video I made many years ago with the colors inverted as well for visibility: https://youtu.be/k2-ZZz5rwQE?si=UaKcidDRbNZOftbd

dredmorbius3• 2 years ago

The "impossible mode" example of a starfield is literally how astronomers have found new bodies (planets, asteroids, comets, supernovae, etc.) since the invention of photography.

Typically this utilised a negative photographic plate (so that bright objects appeared as dark against a light background making their presence easier to detect for our visual system), and the plates were rapidly flipped. The object which moved or suddenly appeared and disappeared was the new element.

This works for nearby moving objects (planets, asteroids, comets) which would track against the stellar background, or distant variable ones (supernovae, variable stars, pulsars) which would appear and disappear (or brighten and fade) over time.

Now of course this is automated and direct sensor readings can be interpreted, but the childs' game was at one time Best Scientific Practice.

Described here, "How are asteroids discovered?" <https://catalina.lpl.arizona.edu/faq/how-are-asteroids-disco...>.

There are archives of these astronomical plates, and there are projects which utilise older observations so recorded to make new discoveries even now (or in the recent past). I'd first learned of this visiting the Lick Observatory on Mt. Hamilton near San Jose some years back. Key was that old plates were used to compare current observations using the same 'scope, an otherwise now-archaic instrument but not without its advantages. As I recall, the astronomer doing the study was the same one who'd made the original plates many decades earlier, and was doing this as his own retirement project. There's a description of similar work (including Lick observations) here:

"Astronomy's Photographic Glass Plates: Demonstrating Value Through Use Cases"

<https://journals.library.ualberta.ca/istl/index.php/istl/art...>

On plate archives:

"Preserving an Astronomical Legacy"

<https://skyandtelescope.org/astronomy-news/preserving-an-ast...>

"APPLAUSE: Archives of Photographic PLates for Astronomical USE"

<https://www.plate-archive.org/applause/info/>

(dylan604 noted this use case earlier: <https://news.ycombinator.com/item?id=42657956>)

bicepjai• 2 years ago

This blog post was nostalgic. Growing up in TamilNadu India, a Tamil weekly magazine called Anandha Vikatan use to have one page of stereogram where an object will be hidden in it. I found it so exciting to do the eye crossing trick to find the image pop up, made me feel great as a kid when my family could not find the image :) fun times

goose-• 2 years ago

What an unexpected and fun read to find on HN.

Bonus tip: while focused on the overlapping image in the middle, jiggle your screen, and the diff will move around while the rest remains static. This helped me solve the impossible challenge instantly.

I'd love to learn more about the underlying mechanism here. Anyone can point me in the right direction?

scottshambaugh• 2 years ago

This I think is an underrated tool for scientific visualization. I made a matplotlib add-on that will let you make stereogram plots of data, and use this cross eyed or parallel eyed techniques to see it in 3D. https://github.com/scottshambaugh/mpl_stereo

notShabu• 2 years ago

This is really cool! it allows you to see 2D charts in 3D without actually rendering anything in 3D

mkoubaa• 2 years ago

Incredible!

n2j3• 2 years ago

The first (easy mode) image worked like magic - I crossed eyes, let them rest and the differences shimmered in a very static 3rd/middle image. Couldn't for the life of me rest my eyes on 2nd and 3rd though. [edit - tried to zoom out, worked on 2nd image too]

kuon• 2 years ago

I have no idea how that is supposed to work. If I cross my eyes I see 3 images and the middle one is a superposition of the two but I don't see any part standing out.

throwaway314155• 2 years ago

It's subtle. You need to make sure the center image is very well in focus first. Then, the "shimmer" appears but it's not really a shimmer so much as a (fairly mild) perceived depth/edge "artifact". It seems to glow but i think this is more to do with it looking a bit like glowy edge based artifacts from 3d movies w/ 3d glasses.

Over2Chars• 2 years ago

tldr: blogger learns how to cross his eyes for fun and "profit".

z02d• 2 years ago

I recently learned about this from one of my favourite German podcasts: https://freakshow.fm/fs286-zurueck-zur-vision (Starting at 2:50h)

raffraffraff4• 2 years ago

Remember the old magic eye posters? Like the static you'd see on an old untuened TV, in monochrome (but some odd colour like puce, cyan or bile)

"It's a schooner"

bambax• 2 years ago

It's funny, it really works.

Was also able to spot the difference on the coffee beans image: https://i.imgur.com/0TcWvWJ.png

ninetyninenine4• 2 years ago

I came into this rolling my eyes thinking he acquired some ability to learn and be humble or some programming or management topic... the typical bs you see on hacker news.

Boy was I wrong. This is an actual super power.

JW_00000• 2 years ago

If you can easily cross / unfocus your eyes, it also allows you to see 3D images easily. Try:

https://www.reddit.com/r/ParallelView/

https://www.reddit.com/r/CrossView/

snvzz• 2 years ago

Funny. I crossed my eyes and found the difference before reading the article.

Somehow expect most people to know this, but I guess that's not the case.

nkrisc3• 2 years ago

Very cool. After a minute I was able to focus on the false “third” image of the overlap of each side, but I couldn’t notice any difference. It did appear to be closer to me than the screen though.

aiono• 2 years ago

When I was little I was doing this on carpet patterns because they suddenly become 3D. It was very fun. But I never realized it could be used for this purpose.

There is also one other similar funny ability I have: Vibrating my eyes. I can willingly vibrate my eyes. I don't think it's any useful ability as I just see shaky when I do it but it's fun to do in front of people. It scares some of them. There is actually a community about it in Reddit: https://www.reddit.com/r/Eyeshakers/

sebastiennight• 2 years ago

Thanks to this article I have successfully taken a two-hour break from HN and my computer screen, on behalf of the massive headache I acquired at the same time as the aforementioned superpower.

keepamovin• 2 years ago

Wow so cool! It really just bounces out. I used to love those Magic Eye books. There's something meditative and calming about that sort of focus. This post was really cool!

2024user• 2 years ago

I can do the 3d images in kids books but cannot make it work for spotting the difference

jheriko• 2 years ago

i didn't use the trick, or read what it was until after i tried for myself. it took me about 7 seconds at a conservative overestimate...

then again, i did outperform my entire national cohort at school in almost every subject by a wide margin... an outlier.

the trick however is very clever, but it wont work in more complicated scenarios where attention to detail matters.

EDIT: after doing the first one near the top i tried the rest. with a bit of warm up its very fast. no tricks needed. maybe a relic of playing these games when younger and having a "once in a generation" level of learning power coupled with training it when very young when learning speed is multiplied by a huge scale factor. i had to zoom the last one, but the other two were incredibly fast, close to immediate. sub second.

EDIT2: the warm up was doing the first image once after reading the first few sentences.

EDIT3: this is not a superpower.

pvo50555• 2 years ago

I can't believe this has 1587 points (already). Has no one here grown up with those Magic Eye books?

cassepipe• 2 years ago

I've discovered I can't cross my eyes. Any techniques ?

funnyfoobar• 2 years ago

Dumb question: How do I cross my eyes? can someone explain this method in detail?

ponorin• 2 years ago

related: if you have a side-by-side 3d image/video you can do the crosseye to see it in 3D without any special display/glasses.

it's just that your eyes are gonna be tired after a movie session.

menzoic2• 2 years ago

This is literally a superpower

menzoic2• 2 years ago

TIL you can learn super powers on the internet

pigeons• 2 years ago

It just feels like I'm going to harm something if I leave them crossed more than a split second and I stop.

shw1n• 2 years ago

One of the coolest "immediate novelty" things I've read in a while

Sent it to my whole family

The way your mind locks in and focuses on the middle one seems a testament to the brain processing behind vision we take for granted

garfieldnate• 2 years ago

Doesn't work if you have lazy-eye, unfortunately! I generally just see whatever my stronger eye sees. It might be a good exercise to improve my weaker eye's sight, though.

yarolig• 2 years ago

By the way... There is a nice old good article about making real time stereograms.

https://developer.nvidia.com/gpugems/gpugems/part-vi-beyond-...

hegzploit• 2 years ago

Cool site that I often use with this trick to impress some friends: https://www.spotthedifference.com/practice.asp?m=2&l=4

ern0• 2 years ago

On Amiga, there was a 3D demo with this trick. You can "jump in" your eyes to the proper position if you hold your finger at the place where the 3d image should appear, ca. 10 cm close to your eyes, and focus on it. You'll be cross-eyed without knowing it.

Also, I was using the trick as a "cheat" when I played Tiny Lands on Nintendo Switch, it's a "spot the difference" game, but with 3d landscapes (you can rotate and zoom): https://www.dekudeals.com/items/tiny-lands

tenthirtyam• 1 year ago

This reminds me of the 4D maze. Let's see if it's still around... yep: https://www.urticator.net/maze/

I tried using it, like the author, to visualize and investigate 4D data. But my stone-age brain, regrettably, seems limited to intuiting only 3 dimensions.

I've acquired a new superpower

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