Background /956 We perceive the world as three-dimensional. The inputs to our visual system,however,are only a pair of two-dimensional projections on the two retinal surfaces. EBUR EBURY Image in left eye Image in right eye depth We perceive the world as three-dimensional.  The inputs to our visual system, however, are only a pair of two-dimensional projections on the two retinal surfaces. Image in left eye Image in right eye depth Background