EFFECTS OF TEXTURE, ILLUMINATION, AND SURFACE REFLECTANCE ON STEREOSCOPIC SHAPE PERCEPTION

Observers viewed computer-generated stereograms of randomly structured smooth surfaces and were required to judge the perceived local orient ation at numerous probe points by adjusting a monocular gauge figure. The surfaces were depicted with specular or Lambertian reflectance fun ctions, either with or without identifiable texture elements, and with varying directions of illumination. The results revealed a strong lin ear correlation between the judged patterns of relief and the actual d epicted objects, though there were systematic differences in the magni tude of depth scaling in the different conditions. In general, the acc uracy and reliability of observers' judgments for the smoothly shaded shiny surfaces was slightly lower than for the textured surfaces and s lightly higher than for the smoothly shaded Lambertian surfaces. The d irection of illumination had no detectable effect on the observers' ju dgments.