Distance Perception in Virtual Environment through Head-mounted Displays

Head-mounted displays (HMDs) are popular and affordable wearable display devices which facilitate immersive and interactive viewing experience. Numerous studies have reported that people typically underestimate distances in HMDs. This dissertation describes a series of research experiments that examined the influence of FOV and peripheral vision on distance perception in HMDs and attempts to provide useful information to HMD manufacturers and software developers to improve perceptual performance of HMD-based virtual environments. This document is divided into two main parts. The first part describes two experiments that examined distance judgments in Oculus Rift HMDs. Unlike numerous studies found significant distance compression, our Experiment I & II using the Oculus DK1 and DK2 found that people could judge distances near-accurately between 2 to 5 meters. In the second part of this document, we describe four experiments that examined the influence of FOV and human periphery on distance perception in HMDs and explored some potential approaches of augmenting peripheral vision in HMDs. In Experiment III, we reconfirmed the peripheral stimulation effect found by Jones et al. using bright peripheral frames. We also discovered that there is no linear correlation between the stimulation and peripheral brightness. In Experiment IV, we examined the interaction between the peripheral brightness and distance judgments using peripheral frames with different relative luminances. We found that there exists a brightness threshold; i.e., a minimum brightness level that\u27s required to trigger the peripheral stimulation effect which improves distance judgments in HMD-based virtual environments. In Experiment V, we examined the influence of applying a pixelation effect in the periphery which simulates the visual experience of having a peripheral low-resolution display around viewports. The result showed that adding the pixelated peripheral frame significantly improves distance judgments in HMDs. Lastly, our Experiment VI examined the influence of image size and shape in HMDs on distance perception. We found that making the frame thinner to increase the FOV of imagery improves the distance judgments. The result supports the hypothesis that FOV influences distance judgments in HMDs. It also suggests that the image shape may have no influence on distance judgments in HMDs

Improving everyday computing tasks with head-mounted displays

The proliferation of consumer-affordable head-mounted displays (HMDs) has brought a rash of entertainment applications for this burgeoning technology, but relatively little research has been devoted to exploring its potential home and office productivity applications. Can the unique characteristics of HMDs be leveraged to improve users’ ability to perform everyday computing tasks? My work strives to explore this question. One significant obstacle to using HMDs for everyday tasks is the fact that the real world is occluded while wearing them. Physical keyboards remain the most performant devices for text input, yet using a physical keyboard is difficult when the user can’t see it. I developed a system for aiding users typing on physical keyboards while wearing HMDs and performed a user study demonstrating the efficacy of my system. Building on this foundation, I developed a window manager optimized for use with HMDs and conducted a user survey to gather feedback. This survey provided evidence that HMD-optimized window managers can provide advantages that are difficult or impossible to achieve with standard desktop monitors. Participants also provided suggestions for improvements and extensions to future versions of this window manager. I explored the issue of distance compression, wherein users tend to underestimate distances in virtual environments relative to the real world, which could be problematic for window managers or other productivity applications seeking to leverage the depth dimension through stereoscopy. I also investigated a mitigation technique for distance compression called minification. I conducted multiple user studies, providing evidence that minification makes users’ distance judgments in HMDs more accurate without causing detrimental perceptual side effects. This work also provided some valuable insight into the human perceptual system. Taken together, this work represents valuable steps toward leveraging HMDs for everyday home and office productivity applications. I developed functioning software for this purpose, demonstrated its efficacy through multiple user studies, and also gathered feedback for future directions by having participants use this software in simulated productivity tasks

A perceptual calibration method to ameliorate the phenomenon of non-size-constancy in hetereogeneous VR displays

The interception of the action-perception loop in virtual reality [VR] causes that understanding the effects of different display factors in spatial perception becomes a challenge. For example, studies have reported that there is not size-constancy, the perceived size of an object does not remain constant as its distance increases. This phenomenon is closely related to the reports of underestimation of distances in VR, which causes remain unclear. Despite the efforts improving the spatial cues regarding display technology and computer graphics, some interest has started to focus on the human side. In this study, we propose a perceptual calibration method which can ameliorate the effects of non-size-constancy in heterogeneous VR displays. The method was validated in a perceptual matching experiment comparing the performance between an HTC Vive HMD and a four-walls CAVE system. Results show that perceptual calibration based on interpupillary distance increments can solve partially the phenomenon of non-size-constancy in VR

Investigating the Usability of a Vibrotactile Torso Display for Improving Simulated Teleoperation Obstacle Avoidance

While unmanned ground vehicle (UGV) teleoperation is advantageous in terms of adaptability and safety, it introduces challenges resulting from the operator\u27s poor perception of the remote environment. Previous literature on the ability of haptic feedback to augment visual displays indicates that UGV obstacle avoidance information may be more meaningfully communicated via vibrotactile torso systems. Presenting this information so that operators can accurately detect the proximity from walls and obstructions could result in a significant reduction in errors, ultimately improving task performance and increasing the usability of teleoperation. The goal of the current study was to determine the degree to which a vibrotactile torso belt could improve UGV teleoperation performance over video feed alone in a simulated environment. Sixty operators controlled a UGV using a simulated video feed, while half also utilized a vibrotactile belt. Results indicated that the vibrotactile display did not improve navigational performance or decrease subjective workload over video feed alone. Possible reasons for this and limitations are discussed

Frontal extents in virtual environments are not immune to underperception

Distance is commonly underperceived by up to 50% in virtual environments (VEs), in contrast to relatively accurate real world judgments. Experiments reported by Geuss, Stefanucci, Creem-Regehr, and Thompson (2012) indicate that the exocentric distance separating two objects in a VE is underperceived when the objects are oriented in the sagittal plane (depth extents), but veridically perceived when oriented in a frontoparallel plane (frontal extents). The authors conclude that, “distance underestimation in the [VE] generalizes to intervals in the depth plane, but not to intervals in the frontal plane.” The current experiment evaluated an alternative hypothesis that the accurate judgments of frontal extents reported by Geuss et al. were due to a fortunate balance of underperception caused by the VE and overperception of frontal relative to depth extents. Participants judged frontal and depth extents in the classroom VE used by Geuss et al. and in a sparser VE containing only a grass-covered ground plane. Judgments in the classroom VE replicated findings by Geuss et al., but judgments in the grass VE show underperception of both depth and frontal extents, indicating that frontal extents are not immune to underperception in VEs

Distortions in Wearable Optics: Comfort, Perception, and Adaptation

Many people have had the experience of viewing the world through optics, such as when wearing corrective spectacles or using augmented and virtual reality devices (AR/VR). The purpose of the optical lenses present in spectacles and devices is to bring images into focus, but they also produce unwanted distortions such as magnification and minification that change the retinal image size or shape of an object. Surprisingly, small changes in retinal image size or shape can have substantial perceptual and physical consequences. While spectacles have been around for centuries, there remains a large gap in the literature on how optical distortions affect the viewer. This dissertation contains experimental investigations related to how optical distortions affect perception and comfort, and how these effects change over time. Chapter 1 establishes a fundamental understanding of the onset of perceptual and physical symptoms produced by optical minification. Chapter 2 investigates how people adapt over time to a specific type of monocular distortion that alters depth and shape perception. Chapter 3 investigates how the visual system interprets the geometry of objects when faced with perceptual disruptions caused by optical distortions. Together this research provides a much-needed foundational understanding of optical distortions from multiple domains

The impact of background and context on car distance estimation

It is well established that people underestimate the distance to objects depicted in virtual environments and two-dimensional (2D) displays. The reasons for the underestimation are still not fully understood. It is becoming more common to use virtual environment displays for driver training and testing and so understanding the distortion of perceived space that occurs in these displays is vital. We need to know what aspects of the display cause the observer to misperceive the distance to objects in the simulated environments. The research reported in this thesis investigated how people estimate distance between themselves and a car in front of them, within a number of differing environmental contexts. Four experiments were run using virtual environment displays of various kinds and a fifth experiment was run in a real-world setting. It was found that distance underestimation when viewing 2D displays is very common, even when familiar objects such as cars are used as the targets. The experiments also verified that people have a greater underestimation of distance in a virtual environment compared to a real-world setting. A surprising and somewhat counterintuitive result was that people underestimate distance more when the scene depicts forward motion of the observer compared to a static view. The research also identified a number of visual features in the display (e.g., texture information) and aspects of the display (e.g., field of view) that affected the perception of distance or that had no effect. The findings should help the designers of driver-training simulators and testing equipment to better understand the types of errors that can potentially occur when humans view two-dimensional virtual environment displays

Blind Direct Walking Distance Judgment Research: A Best Practices Guide

Over the last 30 years, Virtual Reality (VR) research has shown that distance perception in VR is compressed as compared to the real world. The full reason for this is yet unknown. Though many experiments have been run to study the underlying reasons for this compression, often with similar procedures, the experimental details either show significant variation between experiments or go unreported. This makes it difficult to accurately repeat or compare experiments, as well as negatively impacts new researchers trying to learn and follow current best practices. In this paper, we present a review of past research and things that are typically left unreported. Using this and the practices of my advisor as evidence, we suggest a standard to assist researchers in performing quality research pertaining to blind direct walking distance judgments in VR

Compensating for Distance Compression in Audiovisual Virtual Environments Using Incongruence

A key requirement for a sense of presence in Virtual Environments(VEs) is for a user to perceive space as naturally as possible.One critical aspect is distance perception. When judgingdistances, compression is a phenomenon where humanstend to underestimate the distance between themselves andtarget objects (termed egocentric or absolute compression),and between other objects (exocentric or relative compression).Results of studies in virtual worlds rendered throughhead mounted displays are striking, demonstrating significantdistance compression error. Distance compression is a multisensoryphenomenon, where both audio and visual stimuliare often compressed with respect to their distances from theobserver. In this paper, we propose and test a method forreducing crossmodal distance compression in VEs. We reportan empirical evaluation of our method via a study of 3Dspatial perception within a virtual reality (VR) head mounteddisplay. Applying our method resulted in more accurate distanceperception in a VE at longer range, and suggests a modificationthat could adaptively compensate for distance compressionat both shorter and longer ranges. Our results havea significant and intriguing implication for designers of VEs:an incongruent audiovisual display, i.e. where the audio andvisual information is intentionally misaligned, may lead tobetter spatial perception of a virtual scene