Tolerance of temporal delay in virtual environments

To enhance presence, facilitate sensory motor performance, and avoid disorientation or nausea, virtual-reality applications require the perception of a stable environment. End-end tracking latency (display lag) degrades this illusion of stability and has been identified as a major fault of existing virtual-environment systems. Oscillopsia refers to the perception that the visual world appears to swim about or oscillate in space and is a manifestation of this loss of perceptual stability of the environment. The effects of end-end latency and head velocity on perceptual stability in a virtual environment were investigated psychophysically. Subjects became significantly more likely to report oscillopsia during head movements when end-end latency or head velocity were increased. It is concluded that perceptual instability of the world arises with increased head motion and increased display lag. Oscillopsia is expected to be more apparent in tasks requiring real locomotion or rapid head movement.

1. Introduction

In typical applications most imagery in a virtual environment should appear stable in three-dimensional space. A head-coupled or head-slaved virtual reality system attempts to achieve this goal by tracking the position and orientation of the user's head in space. From these measurements and knowledge of the relative position of the head-fixed tracking device to the eye, the vantage point of the eye (or eyes in a stereo display) can be estimated and the appropriate perspective view generated. Inaccuracies and imprecision in tracked head position and orientation result in errors and imprecision in the estimated vantage points.