Our perception of depth is substantially enhanced by the fact that we have binocular vision. This provides us with more precise and accurate estimates of depth and an improved qualitative appreciation of the three-dimensional (3D) shapes and positions of objects. We assessed the link between these quantitative and qualitative aspects of 3D vision. Specifically, we wished to determine whether the realism of apparent depth from binocular cues is associated with the magnitude or precision of perceived depth and the degree of binocular fusion. We presented participants with stereograms containing randomly positioned circles and measured how the magnitude, realism, and precision of depth perception varied with the size of the disparities presented. We found that as the size of the disparity increased, the magnitude of perceived depth increased, while the precision with which observers could make depth discrimination judgments decreased. Beyond an initial increase, depth realism decreased with increasing disparity magnitude. This decrease occurred well below the disparity limit required to ensure comfortable viewing.

With the increase in popularity of consumer virtual reality headsets, for research and other applications, it is important to understand the accuracy of 3D perception in VR. We investigated the perceptual accuracy of near-field virtual distances using a size and shape constancy task, in two commercially available devices. Participants wore either the HTC Vive or the Oculus Rift and adjusted the size of a virtual stimulus to match the geometric qualities (size and depth) of a physical stimulus they were able to refer to haptically. The judgments participants made allowed for an indirect measure of their perception of the egocentric, virtual distance to the stimuli. The data show under-constancy and are consistent with research from carefully calibrated psychophysical techniques. There was no difference in the degree of constancy found in the two headsets. We conclude that consumer virtual reality headsets provide a sufficiently high degree of accuracy in distance perception, to allow them to be used confidently in future experimental vision science, and other research applications in psychology.

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 nonlinearly 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 nonlinear 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.

CCS Concepts•Human-centered computing → Laboratory experiments; •Hardware → Sensors and actuators;The Leap Motion controller allows for a mouse-free alternative to general computing. With 200 frames/second infrared cameras, a 150• field of view and an 8 ft 2 umbrella of interactive space, the Leap Motion has many potential practical applications. The device is advertised as aiming to be placed in new cars, laptops and hospitals, for example, to provide contact-free device control, while reducing the need for attentive button pressing and averting eye focus.We assessed the accuracy of the Leap Motion when the correct hand position is known. Other studies have also assessed the accuracy of the device, tracking either a reference pen manipulated by a robot arm [1], or the positions of participant's fingers while pointing at a computer screen [2]. We assessed the accuracy with which grip aperture (the separation between the thumb and forefinger) can be measured. This gesture is useful for indicating the size of objects, or the separation between points. Thirteen wooden rods were created in centimetre increments between 1 and 13cm. These were held by participants between their thumb and forefinger tips above the Leap Motion, before removing them, but keeping the hand position stable (Figure 1a). Ten trials were completed before checking the size with the rod and repeating for another 10, giving 20 repeats for each size. The endpoints of the participant's fingers were recorded from the Leap Motion using MATLAB and Matleap [3], and the Euclidean distance between the endpoints was calculated.A linear regression was performed on the median separation as measured by Leap Motion, against the actual grip aperture. This accounted for between 94.8 and 98.4% of the variance, across participants. Each participant's regression equation was used to calculate a grip aperture estimate from the Leap Motion data on each trial. The mean, median and RMS error, for each grip aperture, were then calculated for each participant (Figure 1b). The mean RMS was greatest

This study investigated the contribution of stereoscopic depth cues to the reliability of ordinal depth judgments in complex natural scenes. Participants viewed photographs of cluttered natural scenes, either monocularly or stereoscopically. On each trial, they judged which of two indicated points in the scene was closer in depth. We assessed the reliability of these judgments over repeated trials, and how well they correlated with the actual disparities of the points between the left and right eyes' views. The reliability of judgments increased as their depth separation increased, was higher when the points were on separate objects, and deteriorated for point pairs that were more widely separated in the image plane. Stereoscopic viewing improved sensitivity to depth for points on the same surface, but not for points on separate objects. Stereoscopic viewing thus provides depth information that is complementary to that available from monocular occlusion cues.