We are 3D creatures, living in a 3D world but our eyes can show us only two dimensions. The depth that we all think we can see is merely a trick that our brains have learned; a byproduct of evolution putting our eyes on the front of our faces. To prove this, close one eye and try to play tennis.

Do humans see 3D?

Human perception is remarkably flexible: We experience vivid three-dimensional (3D) structure under diverse conditions, from the seemingly random magic-eye stereograms to the aesthetically beautiful, but obviously flat, canvases of the Old Masters.

What do things look like in 2D?

A two-dimensional (2D) object is an object that only has two dimensions, such as a length and a width, and no thickness or height. ... The flat sides of three-dimensional objects are two-dimensional shapes. For example, the sides of most buildings are rectangles.