The combined influence of binocular disparity and shading on pictorial shape

The combined influence of binocular disparity and shading on pictorial shap e was studied. Stimuli were several pairs of stereo photographs of real obj ects. The stereo base was 0, 7, or 14 cm, and the location of the light sou rce was varied over three positions (one from about the viewpoint of the ca mera, one about perpendicular to the line of sight, and one in between the two). Therefore, in total, nine different combinations were studied. Subjec ts had to perform surface attitude settings at about 300 positions in the i mage plane. From the settings, depth maps were calculated on which a princi pal components analysis was performed. It was found that three components w ere enough to account for at least 97.8% of the variance in the data. The f irst component accounted for shape constancy. The effects of the two cues c ould be isolated as a linear combination of the other two components. The e ffects of the disparity and the shading cue variation were found to combine in almost linear fashion.