The Ebbinghaus illusion, also known as Titchner Circles, is a well- known perceptual illusion affecting the perceived size of a disc enclosed by an annulus of either larger or smaller discs. Though many have found highly consistent results with regard to the effect of the illusion on size perception, there have been mixed results when studying its effect on action-based tasks. In this paper, we present a study utilizing a head-worn virtual environment to examine the effect of the Ebbinghaus illusion on depth judgments as measured using a blind-reaching task. We found that participants’ size judgments were symmetrically affected by the classic "large annulus" and "small annulus" configurations, but their distance judgments were asymmetrically affected. Large annulus configurations had no significant effect on distance judgments while small annulus configurations resulted in significant underestimation of target distances. Despite this asymmetry, both configurations resulted in response times of similar magnitude that were significantly longer than those of the non-illusory control condition.

There has long been interest in illusions of self-motion and their perception in virtual environments. Prior work has indicated that an observer's field of view size is an important factor in the perception of self-motion both real and illusory. Restricted fields of view in some virtual reality displays has limited the extent to which this can be studied. In this paper, we discuss a pilot study examining how well observers can discriminate forward motion velocities as viewed through two common, but differing, field of view configurations. We find that observers are quite sensitive to changes in forward motion. The perceived magnitude of this motion is also found to be affected by field of view size with a smaller field of view resulting in slower perceived velocity.

The physiological optics and neurology of vision are topics with much breadth and perhaps even more depth. Though many people have a cursory understanding of the visual system, there are some less-commonly known aspects that are vitally important to virtual environments research and practice. In this paper, we present an elementary discussion of the optical and neural elements involved in the early stages of vision and their relationship to virtual environments.

In this paper, we discuss a generalizable method to measure end-to-end latency. This is the length of time that elapses between when a real-world movement occurs and when the pixels within a head-mounted display are updated to reflect this movement. The method described here utilizes components commonly available at electronics and hobby shops. We demonstrate this measurement method using an HTC Vive and discuss the influence of its low-persistence display on latency measurement.

In this paper, we present three generalizable metrics by which tracking systems for virtual environments can be evaluated. These metrics include positional accuracy, rotational accuracy, and tracking resolution. Additionally, we present methods for acquiring these measurements using components commonly available at hardware and hobby shops. The methods are tested using a consumer-grade virtual reality system but are widely generalizable to most tracking systems, both professional-and consumer-grade.

Spatial perception in virtual environments has been a topic of intense research. Arguably, the majority of this work has focused on distance perception. However, orientation perception is also an important factor. In this paper, we systematically investigate allocentric orientation judgments in both real and virtual contexts over the course of four experiments. A pattern of sinusoidal judgment errors known to exist in 2D perspective displays is found to persist in immersive virtual environments. This pattern also manifests itself in a real world setting using two differing judgment methods. The findings suggest the presence of a radial anisotropy that persists across viewing contexts. Additionally, there is some evidence to suggest that observers have multiple strategies for processing orientations but further investigation is needed to fully describe this phenomenon. We also offer design suggestions for 3D user interfaces where users may perform orientation judgments.

The Depth Light solves the problem of not being able to view the real world, without having to remove the Head Mounted Display, accurately and easily. The Depth Light is activated by a button or trigger press on an HTC Vive controller and consists of a Vive controller, an ultrasonic depth finder, a microcontroller (to send measured distances over serial), a web camera, and a mount for the microcontroller and camera. The device works by finding the distance between the device and the nearest real-world object, taking a sum of these distances, and sending this over serial to a computer as an average. In Unity3D, an object is rendered at the distance sent from the micro controller. This object is then textured with the video feed from the web camera. This object's distance changes in the virtual environment in real time as the Depth Lights micro controller sends new information. As the distance changes the scale of the object also changes, this is to keep the object the same size in the field of vision. The data from the Depth Light is handled by a Unity3D plugin. This plug-in handles all the rendering commands and all of the scaling.

In this article, we detail a series of experiments that examines the effect of vertical field-of-view extension and the addition of non-specific peripheral visual stimulation on gait characteristics and distance judgments in a head-worn virtual environment. Specifically, we examined four field-of-view configurations: a common 60° diagonal field of view (48° × 40°), a 60° diagonal field of view with the addition of a luminous white frame in the far periphery, a field of view with an extended upper edge, and a field of view with an extended lower edge. We found that extension of the field of view, either with spatially congruent or spatially non-informative visuals, resulted in improved distance judgments and changes in observed posture. However, these effects were not equal across all field-of-view configurations, suggesting that some configurations may be more appropriate than others when balancing performance, cost, and ergonomics.

We report the results of an empirical evaluation to examine the carryover effects of calibrations to one of three perturbations of visual and proprioceptive feedback: i) Minus condition (-20% gain) in which a visual stylus appeared at 80% of the distance of a physical stylus, ii) Neutral condition (0% gain) in which a visual stylus was co-located with a physical stylus, and iii) Plus condition (+20% gain) in which the visual stylus appeared at 120% of the distance of the physical stylus. Feedback was shown to calibrate distance judgments quickly within an IVE, with estimates being farthest after calibrating to visual information appearing nearer (Minus condition), and nearest after calibrating to visual information appearing further (Plus condition).

Research in visuo-motor coupling has shown that the matching of visual and proprioceptive information is important for calibrating movement. Many state-of-the art virtual reality (VR) systems, commonly known as immersive virtual environments (IVE), are created for training users in tasks that require accurate manual dexterity. Unfortunately, these systems can suffer from technical limitations that may force de-coupling of visual and proprioceptive information due to interference, latency, and tracking error. We present an empirical evaluation of how visually distorted movements affects users' reach to near field targets using a closed-loop physical reach task in an IVE. We specifically examined the recalibration of movements when the visually reached distance is scaled differently than the physically reached distance. Subjects were randomly assigned to one of three visual feedback conditions during which they reached to target while holding a tracked stylus: i) Condition 1 (-20% gain condition) in which the visual stylus appeared at 80% of the distance of the physical stylus, ii) Condition 2 (0% or no gain condition) in which the visual stylus was co-located with the physical stylus, and iii) Condition 3 (+20% gain condition) in which the visual stylus appeared at 120% of the distance of the physical stylus. In all conditions, there is evidence of visuo-motor calibration in that users' accuracy in physically reaching to the target locations improved over trials. During closed-loop physical reach responses, participants generally tended to physically reach farther in condition 1 and closer in condition 3 to the perceived location of the targets, as compared to condition 2 in which participants' physical reach was more accurate to the perceived location of the target.

In this document we present a method for calibrating head-mounted displays and other display surfaces using an automated, low-cost camera system. A unique aspect of this method is that the calibration of geometric distortions, field of view, and chromatic aberration are achieved without the need for a priori knowledge of the display system's intrinsic parameters. This method operates by capturing and storing the pixel space locations of a series of real world control points. These control points are then used as ground truth references by which virtual space transformations can be automatically generated for a display system.

In this document we discuss a study that investigates the effect of eye position on the apparent location of imagery presented in an off-the-shelf head worn display. We test a range of reasonable eye positions that may result from person-to-person variations in display placement and interpupillary distances. It was observed that the pattern of geometric distortions introduced by the display's optical system changes substantially as the eye moves from one position to the next. These visual displacements can be on the order of several degrees and increase in magnitude towards the peripheral edges of the field of view. Though many systems calibrate for interpupillary distance and optical distortions separately, this may be insufficient as eye position influences distortion characteristics.

The following series of experiments explore the effect of static peripheral stimulation on the perception of distance and spatial scale in a typical head-mounted virtual environment. It was found that applying constant white light in an observer's far periphery enabled the observer to more accurately judge distances using blind walking. An effect of similar magnitude was also found when observers estimated the size of a virtual space using a visual scale task. The presence of the effect across multiple psychophysical tasks provided confidence that a perceptual change was, in fact, being invoked by the addition of the peripheral stimulation. These results were also compared to observer performance in a very large field of view virtual environment and in the real world. The subsequent findings raise the possibility that distance judgments in virtual environments might be considerably more similar to those in the real world than previous work has suggested.

As wider field-of-view displays become more common, the question arises as to whether or not data collected on these displays are comparable to those collected with smaller field-of-view displays. This document describes a pilot study that aimed to address these concerns by comparing medium-field distance judgments in a 60° FOV display, a 150° FOV display, and a simulated 60° FOV within the 150° FOV display. The results indicate that participants performed similarly in both the actual and simulated 60° FOV displays. On average, participants in the 150° FOV display improved distance judgments by 13% over the 60° FOV displays.

A previous study indicated that peripheral visual information strongly affects the judgment of egocentric distances for users of immersive virtual environments. The experiment described in this document aimed to investigate if these effects could be explained in terms of changes in gait caused by visual information in the extreme periphery. Three conditions with varying degrees of peripheral occlusion were tested and participants' walking characteristics measured. The results indicate that the improvements in distance judgments, as peripheral information increases, can only partially be explained in terms of gait modification, but likely involve both changes in the characteristics of gait and other spatial or movement parameters.

In this abstract we describe an experiment that measured depth judgments in optical see-through augmented reality (AR) at near-field reaching distances of ~ 24 to ~ 56 cm. The 2×2 experiment crossed two depth judgment tasks, perceptual matching and blind reaching, with two different environments, a real-world environment and an augmented reality environment. We designed a task that used a direct reaching gesture at constant percentages of each participant's maximum reach; our task was inspired by previous work by Tresilian and Mon-Williams [6] that found very accurate blind reaching results in a real-world environment.

A frequently observed problem in virtual environments is the underestimation of egocentric depth. This problem has been described numerous times and with widely varying degrees of severity. Though there has been considerable progress made in modifying observer behavior to compensate for these misperceptions, the question of why these errors exist is still an open issue. The study detailed in this document presents the preliminary findings of a large, between-subjects experiment (N=98) that attempts to identify and quantify the source of a pattern of adaptation and improved accuracy in the absence of explicit feedback found in Jones et al. [1].

In this poster abstract we describe an experiment that measured depth judgments in optical see-through augmented reality at near-field distances of 34 to 50 centimeters. The experiment compared two depth judgment tasks: perceptual matching, a closed-loop task, and blind reaching, a visually open-loop task. The experiment tested each of these tasks in both a real-world environment and an augmented reality environment, and used a between-subjects design that included 40 participants. The experiment found that matching judgments were very accurate in the real world, with errors on the order of millimeters and very little variance. In contrast, matching judgments in augmented reality showed a linear trend of increasing overestimation with increasing distance, with a mean overestimation of ~1 cm. With reaching judgments participants underestimated ~4.5 cm in both augmented reality and the real world. We also discovered and solved a calibration problem that arises at near-field distances.