Binocular vision and motion-in-depth.

When an object moves in three dimensions, the two eyes' views of the world deliver slightly different information to the visual system, providing binocular cues to depth and motion-in-depth. This short review describes the two main sources of binocular information, namely, changing disparity over time and interocular velocity differences; this could be used for the perception of motion-in-depth. We discuss the evidence obtained in recent years on the extent to which each of them is used in human vision. We also highlight outstanding questions and issues in the field that have yet to be addressed.