  Immersive computer graphics systems strive to generate perceptually realistic
user experiences. Current-generation virtual reality (VR) displays are
successful in accurately rendering many perceptually important effects,
including perspective, disparity, motion parallax, and other depth cues. In
this article, we introduce ocular parallax rendering, a technology that
accurately renders small amounts of gaze-contingent parallax capable of
improving depth perception and realism in VR. Ocular parallax describes the
small amounts of depth-dependent image shifts on the retina that are created as
the eye rotates. The effect occurs because the centers of rotation and
projection of the eye are not the same. We study the perceptual implications of
ocular parallax rendering by designing and conducting a series of user
experiments. Specifically, we estimate perceptual detection and discrimination
thresholds for this effect and demonstrate that it is clearly visible in most
VR applications. Additionally, we show that ocular parallax rendering provides
an effective ordinal depth cue and it improves the impression of realistic
depth in VR.
