The use of subtle illumination cues for human judgement of spatial layout

The interaction of light with surfaces creates complex lighting effects that provide potentially useful information about the spatial relationships between objects. Previous research has shown cast shadows to be effective in determining the 3D layout of a scene. Interreflections are another source of information for spatial relationships; these, however, have been largely ignored in studies of human perception. The purpose of this study was to determine the effectiveness of interreflection for providing cues to contact, and to investigate how interreflection and shadow information combine in the perception of object contact.