Surfaces in the Mind’s Eye

Abstract

“Pictorial reliefs” are surfaces of objects in pictorial space, the mental entity that happens to human observers when looking at (or rather: into) pictures. We discuss the structure of pictorial relief and pictorial space. It is determined by the nature of various “depth cues” which are intrinsically ambiguous. General arguments suggest that the structure of pictorial relief is invariant under a certain group of affinities that preserve planarity in general and the picture plane in particular. The subgroup of depth scalings has already been identified as of crucial importance in vision by sculptors. We have also found evidence of the occurrence of shears involving both the picture plane dimensions and depth. Observers apparently use these to “adjust their mental perspective”.