Double Take: Geometry, Perspective, and Optical Illusions

Abstract: Perspective geometry, so it's said, was the art that made paintings seem realistic and true to life.  Yet the same artistic techniques—and by extension, the same geometry—can create images that astound and confound us.  We provide a carnival of such examples, from special effects in the movies, to sculptures that seem to move as we move, to hidden objects, and to objects whose mirror images transform them into other beings.