From DT Online
Optical Illusions occur often when 2D drawings create confusing views of reality. These are more specifically known as ‘literal’ optical illusions
Perspective drawing is an optical illusion in that a 2D drawing is made to look like a 3D object. Converging parallel lines, like railway tracks give the illusion of depth and distance (see ‘Ponzo illusion’) and parallel vertical lines in a perspective drawing can sometimes appear curved (see ‘Hering illusion’)
In Isometric drawing, beginners often get confused about which surfaces are at the front and which to the rear. This is a well-known ambiguity (see ‘Necker cube’) and the artist M.C. Escher exploited this in many of his paintings.