Shifting Cube: A Visual Illusion

There are two cubes: a small one and a big one. Or is it just a small cube set up in a corner formed by three planes? Or, perhaps, it's a big cube one of whose corners was cut off?

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Shifting cube illusion - is this a cube in a corner or a cube without a corner?

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As with the Necker cube, the brain tries to make up for the absence of perspective clues. There are at least a couple of ways to do that. It is easy to make it see either one or the other.

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