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But these aren't so much visual illusions as they are camera illusions. Their whole premise is the fact that they are a 2D projection of 3D objects. There are multiple 3D objects that project to the exact same 2D object, so I don't understand why there has to be a mistake involved.

That would be like saying two times ten is twenty, and four times five is twenty, so division has been designed incorrectly.

I guess the premise is that, given that multiple 3D objects could correspond to what we are seeing, we consistently choose the wrong one. Perhaps to borrow your analogy, it would be sort of like if, upon seeing a multiplication problem equal to twenty, we automatically assumed 2x10, and we perceived an illusion whenever the problem was actually 4x5.

We consistently choose the overwhelmingly more likely one. That's the reasonable thing to do, and it shows in the fact that these illusions take considerable effort to construct.

Our vision works by a projection on to a 2D surface in our eyes. This type of illusion does rely on having a particular vantage point, though...

We rely pretty heavily on 'synthetic aperture' reconstruction. Close one eye, look at a scene with objects at various distances. It looks flat - near and far are hard to distinguish. Move your head right and left (still one eye closed) - the objects jump out at you, nearer ones clearly 'in front' of further ones.

So the 2D retina is just the start - our neural processing jelly is reconstructing a 3D image from it continuously. This affects how we perceive the world drastically. Lots of room to fool the algorithms. Not because the hardware (eye/retina) is faulty; because using fairly simple and efficient hardware, our incredible neural processing elicits tremendous results!

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