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Comment by grishka | Hacker News Reader

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.

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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

> 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.

That's exactly it. You have to bring the "copy" of the left side to overlap with the "original" right side. Then move forward/backward until the overlapped 2 come into focus. The shimmering should stick out, was so shocking when it finally clicked for me.

I used put my finger halfway to the object, look at my finger until the crossed images in the background converge, then remove my finger and let my eyes stay in the same spot.

Now I can do it without the finger.

> until the crossed images in the background converge

that's the issue! like an OP i never was able to "converge" the images. for me it is phisically impossible: they are too far apart and never come closer. maybe because i have an astigmatism.

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.

Suffering from the same exact plight

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.

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.

I seem to have the same thing. I can't get double images or any tricks at all.

I tried putting folded paper between my eyes to divide the images in such a way that I would only see left side with my left eye, and right side with my right, and I can alternate between image from left and image from right, but I can never see the image at once, or right side when I'm using my left eye.

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.

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

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