Depth cues

Depth cues are psychological factors that aid a brain in perceiving depth in visual imagery.

There are many depth cues, including motion parallax, ocular parallax, vergence of the eyes (the angle that the eyes make relative to each other), and accommodation of the eye (the focus of each eye).

Most VR headsets only reproduce depth cues that happen due to binocular disparity. They operate at a fixed focal depth which means that accommodation of the eye is fixed and does not change. This results in a vergence-accommodation conflict.

Other depth cues include relative size, meaning that an object looks smaller the further away it is, and relative motion, meaning that objects that are further away tend to move more slowly.

When designing an AR or VR headset, the depth cues of ocular parallax and accommodation need to be taken into account if the developer of the headset wants the users to be able to run applications that require high visual fidelity closer than one meter away from the user.