Reexamining the Relationship Between Stereopsis and Motion Parallax.

Depth perception depends on two powerful cues, stereopsis and motion parallax, that share similar geometric foundations but operate under distinct constraints. When observer motion is self-generated and the scene is stationary, the two can produce comparable depth percepts. However, disparity generally supports finer discrimination and more accurate depth magnitude percepts. Real-world depth perception from both cues is complicated by eye movements and matching ambiguity, but motion parallax faces additional challenges due to head movements and the presence of object and scene motion. Empirical studies and cue combination models show that the interaction of the two cues is nonlinear, with stereopsis often dominating depth percepts when both cues are available. These issues are increasingly relevant to immersive displays, where head tracking restores natural parallax but optical and geometric mismatches distort the resulting perceived depth. Understanding how the visual system integrates disparity and parallax remains essential for both theory and application.