HMD-based Virtual Environments Research Articles

A Comparison of Distance Estimation in HMD-Based Virtual Environments with Different HMD-Based Conditions

Underestimation of egocentric distances in immersive virtual environments using various head-mounted displays (HMDs) has been a puzzling topic of research interest for several years. As more commodity-level systems become available to developers, it is important to test the variation of underestimation in each system since reasons for underestimation remain elusive. In this article, we examine several different systems in two experiments and comparatively evaluate how much users underestimate distances in each one. To observe distance estimation behavior, a standard indirect blind walking task was used. An Oculus Rift DK1, weighted Oculus Rift DK1, Oculus Rift DK1 with an artificially restricted field of view, Nvis SX60, Nvis SX111, Oculus Rift DK2, Oculus Rift consumer version (CV1), and HTC Vive were tested. The weighted and restricted field of view HMDs were evaluated to determine the effect of these factors on distance underestimation; the other systems were evaluated because they are popular systems that are widely available. We found that weight and field of view restrictions heightened underestimation in the Rift DK1. Results from these conditions were comparable to the Nvis SX60 and SX111. The Oculus Rift DK1 and CV1 possessed the least amount of distance underestimation, but in general, commodity-level HMDs provided more accurate estimates of distance than the prior generation of HMDs.

Immersive Gesture Interfaces for Navigation of 3D Maps in HMD-Based Mobile Virtual Environments

3D maps such as Google Earth and Apple Maps (3D mode), in which users can see and navigate in 3D models of real worlds, are widely available in current mobile and desktop environments. Users usually use a monitor for display and a keyboard/mouse for interaction. Head-mounted displays (HMDs) are currently attracting great attention from industry and consumers because they can provide an immersive virtual reality (VR) experience at an affordable cost. However, conventional keyboard and mouse interfaces decrease the level of immersion because the manipulation method does not resemble actual actions in reality, which often makes the traditional interface method inappropriate for the navigation of 3D maps in virtual environments. From this motivation, we design immersive gesture interfaces for the navigation of 3D maps which are suitable for HMD-based virtual environments. We also describe a simple algorithm to capture and recognize the gestures in real-time using a Kinect depth camera. We evaluated the usability of the proposed gesture interfaces and compared them with conventional keyboard and mouse-based interfaces. Results of the user study indicate that our gesture interfaces are preferable for obtaining a high level of immersion and fun in HMD-based virtual environments.

Affordance Judgments in HMD-Based Virtual Environments

People judge what they can and cannot do all the time when acting in the physical world. Can I step over that fence or do I need to duck under it? Can I step off of that ledge or do I need to climb off of it? These qualities of the environment that people perceive that allow them to act are called affordances. This article compares people’s judgments of affordances on two tasks in both the real world and in virtual environments presented with head-mounted displays. The two tasks were stepping over or ducking under a pole, and stepping straight off of a ledge. Comparisons between the real world and virtual environments are important because they allow us to evaluate the fidelity of virtual environments. Another reason is that virtual environment technologies enable precise control of the myriad perceptual cues at work in the physical world and deepen our understanding of how people use vision to decide how to act. In the experiments presented here, the presence or absence of a self-avatar—an animated graphical representation of a person embedded in the virtual environment—was a central factor. Another important factor was the presence or absence of action, that is, whether people performed the task or reported that they could or could not perform the task. The results show that animated self-avatars provide critical information for people deciding what they can and cannot do in virtual environments, and that action is significant in people’s affordance judgments.

The Effect of Viewing a Self-Avatar on Distance Judgments in an HMD-Based Virtual Environment

Few HMD-based virtual environment systems display a rendering of the user's own body. Subjectively, this often leads to a sense of disembodiment in the virtual world. We explore the effect of being able to see one's own body in such systems on an objective measure of the accuracy of one form of space perception. Using an action-based response measure, we found that participants who explored near space while seeing a fully-articulated and tracked visual representation of themselves subsequently made more accurate judgments of absolute egocentric distance to locations ranging from 4 m to 6 m away from where they were standing than did participants who saw no avatar. A nonanimated avatar also improved distance judgments, but by a lesser amount. Participants who viewed either animated or static avatars positioned 3 m in front of their own position made subsequent distance judgments with similar accuracy to the participants who viewed the equivalent animated or static avatar positioned at their own location. We discuss the implications of these results on theories of embodied perception in virtual environments.

Head-Mounted Displays for Clinical Virtual Reality Applications: Pitfalls in Understanding User Behavior while Using Technology

The use of virtual environments with head-mounted displays (HMDs) offers unique assets to the evaluation and therapy of clinical populations. However, research examining the effects of this technology on clinical populations is sparse. Understanding how wearers interact with the HMD is vital. Discomfort leads to altered use of the HMD that could confound performance measures; the very measures which might be used as tools for clinical decision making. The current study is a post-hoc analysis of the relationship between HMD use and HMD comfort. The analysis was conducted to examine contributing factors for a high incidence of simulator sickness observed in an HMD-based driving simulator. Pearson correlation analysis was used to evaluate objective and subjective measures of HMD performance and self-reported user comfort ratings. The results indicated weak correlations between these variables, indicating the complexity of quantifying user discomfort and HMD performance. Comparison of two case studies detailing user behavior in the virtual environment demonstrates that selected variables may not capture how individuals use the HMD. The validity and usefulness of the HMD-based virtual environments must be understood to fully reap the benefits of virtual reality (VR) in rehabilitation medicine.