Contributions of Pictorial and Binocular Cues to the Perception of Distance in Virtual Reality

We assessed the contribution of binocular disparity and the pictorial cues of linear perspective, texture, and scene clutter to the perception of distance in consumer virtual reality. As additional cues are made available, distance perception is predicted to improve, as measured by a reduction in systematic bias, and an increase in precision. We assessed (1) whether space is non-linearly distorted; (2) the degree of size constancy across changes in distance; and (3) the weighting of pictorial versus binocular cues in VR. In the first task, participants positioned two spheres so as to divide the egocentric distance to a reference stimulus (presented between 3 and 11 m) into three equal thirds. In the second and third tasks, participants set the size of a sphere, presented at the same distances and at eye-height, to match that of a hand-held football. Each task was performed in four environments varying in the available cues. We measured accuracy by identifying systematic biases in responses, and precision as the standard deviation of these responses. While there was no evidence of non-linear compression of space, participants did tend to underestimate distance linearly, but this bias was reduced with the addition of each cue. The addition of binocular cues, when rich pictorial cues were already available, reduced both the bias and variability of estimates. These results show that linear perspective and binocular cues, in particular, improve the accuracy and precision of distance estimates in virtual reality across a range of distances typical of many indoor environments.