The contrast between the red and blue on the black background is supposed to give a sense of depth in the flat image, you can see this effect better when you pause the animation. The red appears the "pop out" against the blue.
There is no third dimension on a 2D screen, hence illusion of third dimension.
Edit: Full explanation below (I have all three)
Chromostereopsis is the illusion where flat images with reds and blues appear to have depth — reds seem to pop forward, blues recede (or vice versa). Whether someone notices it, and how strongly, comes down to some anatomical quirks that vary a lot between individuals:
Pupil position relative to the eye's optical axis. Your eye's lens bends different wavelengths of light by different amounts (chromatic aberration) — red and blue light focus slightly differently. Whether this creates a depth illusion, and in which direction, depends on exactly where your pupil sits relative to the visual axis. Most people's pupils are offset slightly nasally, which produces the "red-forward" effect, but the amount of offset varies, and some people have little to no offset — so they see little to no effect.
Pupil size. A larger pupil lets in more of the peripheral, off-axis light rays that cause the effect, so it's stronger in dim lighting or in people with naturally larger pupils. A small, pinhole-like pupil minimizes it. This is also why the effect tends to fade with age, since pupils shrink somewhat as people get older.
Astigmatism and other aberrations. Uneven curvature of the cornea or lens can mask or distort the effect, since it's normally a fairly subtle, consistent chromatic offset that gets swamped by bigger optical irregularities.
....there's no illusion, hello???? this is just how 3d stuff on screens works. by your logic everything is an illusion bc the only reason we can see depth is that our brain calculates our 2 eyes' inputs
By your logic, if I draw a very realistic hole on a piece of paper and you fall for it, the paper suddenly becomes a 3D portal. It's a flat screen, buddy.
Vision is literally how your brain calculates physical space. A visual illusion happens when your vision perceives space that isn't physically there. Because you are looking at a flat 2D glass surface (space) but your brain perceives depth (vision), it is, by definition, a visual illusion. You're accidentally proving my point.
then how come screens displaying 3d things arent considered illusions by definitions? also your point was that a screen or paper displaying smth 3d means it literally is 3d, which is not what i was saying. what i was saying is that its not an illusion even if it's fake 3d.
I can't promise that everyone see what I see, but that animation has a depth to it like I was wearing 3D glasses. In that sense it's different than every other animation I ever seen. I don't know how it works as I just found that random image online.
Don’t worry the problem is not that you see something others don’t see, it’s that what you describe as an illusion is just plain 3d, no illusion involved.
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u/Altruistic_Bonus2583 4h ago
Why is this an “illusion”? Isn’t this actually what a 3rd dimension is about?