Abstract

The motion of an object’s image relative to its casted shadow is a potential depth cue that has received comparatively little attention. Our previous work has shown this cue to be very effective in eliciting percepts of 3-D motion. In this study, we investigate the interaction of the shadow cue with a more well-studied depth cue, namely, the change of size of an object’s image. An open room was rendered in perspective projection, in which a ball was given an oscillating motion. From the elevation of the center of the ball in the picture plane, the depth of the ball is ambiguous. When a moving shadow is added to the scene, however, the distance between the ball and its shadow is sufficient to produce a percept of motion in depth. Changing the size of the ball as it moves can similarly determine the motion percept. We combined in a consistent or contradictory way the information provided by these two cues. The resulting percept is a weighted average of the interpretations if the cues were presented alone, suggesting a cooperative process.

© 1992 Optical Society of America