THE PERCEPTION OF SURFACE ORIENTATION FROM MULTIPLE SOURCES OF OPTICAL INFORMATION

An orientation matching task was used to evaluate observers' sensitivi ty to local surface orientation at designated probe points on randomly shaped 3-D objects that were optically defined by texture, lambertain shading, or specular highlights. These surfaces could be stationary o r in motion, and they could be viewed either monocularly or stereoscop ically, in all possible combinations. It was found that the deformatio ns of shading and/or highlights (either over time or between the two e yes' views) produced levels of performance similar to those obtained f or the optical deformations of textured surfaces. These findings sugge st that the human visual system utilizes a much richer array of optica l information to support its perception of shape than is typically app reciated.