An anamorphosis is a deformed image that appears in its true shape when viewed in a particular way. A catoptric anamorphosis is viewed through a distorting mirror. An oblique anamorphosis must be seen from a particular, oblique angle.
Julian Beever is an English artist who specializes in oblique anamorphosis street drawings, which he does on pavements around Europe. When viewed from the right angle the drawings kind of "pop-up" out of the pavement at the viewer, and take on a life of their own.
Read more about this in the ever fascinating Proceedings of the Athanasius Kircher Society
Learn more about anamorphosis in general at anamorphosis.com
