The IEEE VR Steering Committee congratulates and offers gratitude to the enormous efforts of the IEEE VR Conference Organizing Committees—with special recognition for the multiple years of hard work of the General Chairs, Carolina Cruz-Neira, Greg Welch, and Xubo Yang. To realize the conference requires a sizeable, motivated team of volunteers to work with the IEEE conference management team. Maintaining the conference’s status as the premier international virtual reality conference is a testament to the commitment of all the organizers and participants that make up the IEEE Virtual Reality community.

In this abstract, we discuss the demand for replication and extension efforts related to two seminal studies focused on virtual reality (VR) locomotion interfaces, initially centered around a VR implementation of the Visual Cliff, often referred to as Virtual Pit. The original experiments by Slater et al. (1995) and Usoh et al. (1999) compared different locomotion methods, including Real Walking, Walking-in-Place, and Flying/Steering, with a focus on presence and ease of use. We discuss the importance of these studies for the field, motivate replication efforts focused on these studies, discuss potential confounding factors, and present considerations for a concerted effort to reproduce the findings with state-of-the-art VR systems and measures, extensions to locomotion methods like Teleportation, and means to support future replications and extensions.

The IEEE VR Steering Committee congratulates and offers gratitude to the enormous efforts of the IEEE VR Conference Organizing Committees — with special recognition for the multiple years of hard work of the General Chairs, Xubo Yang, Kun Zhou, Tobias Langlotz, and Stephan Lukosch. To realize the conference requires a sizeable, motivated team of volunteers to work with the IEEE conference management team. Maintaining the conference's status as the premier international virtual reality conference is a testament to the commitment of all the organizers and participants that make up the IEEE Virtual Reality community.

This work addresses cybersickness, a major barrier to successful long-exposure immersive virtual reality (VR) experiences since user discomfort frequently leads to prematurely ending such experiences. Starting from sensory conflict theory, we posit that if a vibrating floor delivers vestibular stimuli that minimally match the vibration characteristics of a scenario, the size of the conflict between the visual and vestibular senses will be reduced and, thus, the incidence and/or severity of cybersickness will also be reduced. We integrated a custom-built, computer-controlled vibrating floor in our VR system. To evaluate the system, we implemented a realistic off-road vehicle driving simulator in which participants rode multiple laps as passengers on an off-road course. We programmed the floor to generate vertical vibrations similar to those experienced in real off-road vehicle travel. The scenario and driving conditions were designed to be cybersickness-inducing for users in both the Vibration and No-vibration conditions. We collected subjective and objective data for variables previously shown to be related to levels of cybersickness or presence. These included presence and simulator sickness questionnaires (SSQ), self-rated discomfort levels, and the physiological signals of heart rate, galvanic skin response (GSR), and pupil size. Comparing data between participants in the Vibration group (N=11) to the No-Vibration group (N=11), we found that Delta-SSQ Oculomotor response and the GSR physiological signal, both known to be positively correlated with cybersickness, were significantly lower (with large effect sizes) for the Vibration group. Other variables differed between groups in the same direction, but with trivial or small effect sizes. The results indicate that the floor vibration significantly reduced some measures of cybersickness.

Presence has been studied in the context of virtual environments for nearly thirty years, but the field has yet to reach consensus on even basic issues of definition and measurement, and there are many open research questions. We gather many of these open research questions and systematically group them according to what we believe are five key constructs that inform user experience in virtual environments: immersion, coherence, Place Illusion, Plausibility Illusion, and presence. We also report on the design and results of a study that investigated the effects of immersion and coherence on user experience in a stressful virtual visual cliff environment. In this article, each participant experienced a given VE in one of four conditions chosen from a 2x2 design: high or low levels of immersion and high or low levels of coherence. We collected both questionnaire-based and physiological metrics. Several existing presence questionnaires could not reliably distinguish the effects of immersion from those of coherence. They did, however, indicate that high levels of both together result in higher presence, compared any of the other three conditions. This suggests that "breaks in PI" and "breaks in Psi" belong to a broader category of "breaks in experience," any of which result in a degraded user experience. Participants' heart rates responded markedly differently in the two coherence conditions; no such difference was observed across the immersion conditions. This indicates that a VE that exhibits unusual or confusing behavior can cause stress in a user that affects physiological responses, and that one must take care to eliminate such confusing behaviors if one is using physiological measurement as a proxy for subjective experience in a VE.

Many virtual locomotion interfaces allowing users to move in virtual reality have been built and evaluated, such as redirected walking (RDW), walking-in-place (WIP), and joystick input. RDW has been shown to be among the most natural and immersive as it supports real walking, and many newer methods further adapt RDW to allow for customization and greater immersion. Most of these methods have been demonstrated to work with vision, in this paper we evaluate the ability for a general distractor-based RDW framework to be used with only auditory display. We conducted two studies evaluating the differences between RDW with auditory distractors and other distractor modalities using distraction ratio, virtual and physical path information, immersion, simulator sickness, and other measurements. Our results indicate that auditory RDW has the potential to be used with complex navigational tasks, such as crossing streets and avoiding obstacles. It can be used without designing the system specifically for audio-only users. Additionally, sense of presence and simulator sickness remain reasonable across all user groups.

This paper presents the implementation and evaluation of a 50,000-pose-sample-per-second, 6-degree-of-freedom optical head tracking instrument with motion-to-pose latency of 28μs and dynamic precision of 1-2 arcminutes. The instrument uses high-intensity infrared emitters and two duo-lateral photodiode-based optical sensors to triangulate pose. This instrument serves two purposes: it is the first step towards the requisite head tracking component in sub- 100μs motion-to-photon latency optical see-through augmented reality (OST AR) head-mounted display (HMD) systems; and it enables new avenues of research into human visual perception - including measuring the thresholds for perceptible real-virtual displacement during head rotation and other human research requiring high-sample-rate motion tracking. The instrument's tracking volume is limited to about 120×120×250 but allows for the full range of natural head rotation and is sufficient for research involving seated users. We discuss how the instrument's tracking volume is scalable in multiple ways and some of the trade-offs involved therein. Finally, we introduce a novel laser-pointer-based measurement technique for assessing the instrument's tracking latency and repeatability. We show that the instrument's motion-to-pose latency is 28μs and that it is repeatable within 1-2 arcminutes at mean rotational velocities (yaw) in excess of 500°/sec.

We report on the design and results of two experiments investigating Slater's Place Illusion (PI) and Plausibility Illusion (Psi) in a virtual visual cliff environment. PI (the illusion of being in a place) and Psi (the illusion that the depicted events are actually happening) were proposed by Slater as orthogonal components of virtual experience which contribute to realistic response in a VE. To that end, we identified characteristics of a virtual reality experience that we expected to influence one or the other of PI and Psi. We designed two experiments in which each participant experienced a given VE in one of four conditions chosen from a 2×2 design: high or low levels of PI-eliciting characteristics (that is, immersion) and high or low levels of Psi-eliciting characteristics. Following Skarbez, we use the term "coherence" for those characteristics which contribute to Psi, parallel to the use of "immersion" for characteristics that contribute to PI. We collected both questionnaire-based and physiological metrics. Several existing presence questionnaires could not reliably distinguish the effects of PI from those of Psi. They did, however, indicate that high levels of PI-eliciting characteristics and Psi-eliciting characteristics together result in higher presence, compared any of the other three conditions. This suggests that "breaks in PI" and "breaks in Psi" belong to a broader category of "breaks in experience," any of which result in a degraded user experience. Participants' heart rates, however, responded markedly differently in the two Psi conditions; no such difference was observed across the PI conditions. This indicates that a VE that exhibits unusual or confusing behavior can cause stress in a user that affects physiological responses, and that one must take care to eliminate such confusing behaviors if one is using physiological measurement as a proxy for subjective experience in a VE.

For generalized augmented reality to be feasible, the augmenting elements must be visible in varied environments and under rapidly changing, high dynamic range lighting, from bright sunlight to deep shadows. We present a high dynamic range, optical see-through, augmented reality display that dynamically adjusts the brightness of the virtual imagery to match the current brightness of the real scene. Critical components include the spatial brightness sensor array and the positional brightness image intensity matcher. The color, scene-adaptive HDR display system is based on a high-rate (15 kHz) DMD projector using a high-speed RGB LED illuminator, each color with independent 16 bit intensity control for each binary DMD frame. The critical input to the intensity matching algorithm is the output of an array of high sensitivity light sensors. This paper discusses the implementation of the system and reports performance via still and video demonstrations under a variety of lighting conditions.

We report on the design and results of an experiment investigating Slater's Place Illusion (PI) and Plausibility Illusion (Psi) in a virtual visual cliff environment. Existing presence questionnaires could not reliably distinguish the effects of PI from those of Psi. They did, however, indicate that high levels of PI-eliciting characteristics and Psi-eliciting characteristics together result in higher presence, compared to any of the other three conditions. Also, participants' heart rates responded markedly differently in the two Psi conditions; no such difference was observed across the PI conditions.

We discuss the design and results of an experiment investigating Plausibility Illusion in virtual human (VH) interactions, in particular, the coherence of conversation with a VH. This experiment was performed in combination with another experiment evaluating two display technologies. As that aspect of the study is not relevant to this poster, it will be mentioned only in the Materials section. Participants who interacted with a low-coherence VH looked around the room markedly more than participants interacting with a high-coherence VH, demonstrating that the level of coherence of VHs can have a detectable effect on user behavior and that head and gaze behavior can be used to evaluate the quality of a VH interaction.

We report on the design and results of an experiment investigating factors influencing Slater's Plausibility Illusion (Psi) in virtual environments (VEs). Slater proposed Psi and Place Illusion (PI) as orthogonal components of virtual experience which contribute to realistic response in a VE. PI corresponds to the traditional conception of presence as "being there," so there exists a substantial body of previous research relating to PI, but very little relating to Psi. We developed this experiment to investigate the components of plausibility illusion using subjective matching techniques similar to those used in color science. Twenty-one participants each experienced a scenario with the highest level of coherence (the extent to which a scenario matches user expectations and is internally consistent), then in eight different trials chose transitions from lower-coherence to higher-coherence scenarios with the goal of matching the level of Psi they felt in the highest-coherence scenario. At each transition, participants could change one of the following coherence characteristics: the behavior of the other virtual humans in the environment, the behavior of their own body, the physical behavior of objects, or the appearance of the environment. Participants tended to choose improvements to the virtual body before any other improvements. This indicates that having an accurate and well-behaved representation of oneself in the virtual environment is the most important contributing factor to Psi. This study is the first to our knowledge to focus specifically on coherence factors in virtual environments.

Head motion during real walking is complex: The basic translational path is obscured by head bobbing. Many VE applications would be improved if a bobbing-free path were available. This paper introduces a model that describes head position while walking in terms of a bobbing free path and the head bobs. We introduce two methods to approximate the model from head-track data.

In order to better understand how scene motion is perceived in immersive virtual environments, we measured scene-motion thresholds under different conditions across three experiments. Thresholds were measured during quasi-sinusoidal head yaw, single left-to-right or right-to-left head yaw, different phases of head yaw, slow to fast head yaw, scene motion relative to head yaw, and two scene illumination levels. We found that across various conditions 1) thresholds are greater when the scene moves with head yaw (corresponding to gain < 1:0) than when the scene moves against head yaw (corresponding to gain > 1:0), and 2) thresholds increase as head motion increases.

Redirected Free Exploration with Distractors (RFEDs) is a large-scale real-walking locomotion interface developed to enable people to walk freely in Virtual Environments (VEs) that are larger than the tracked space in their facility. This paper describes the RFED system in detail and reports on a user study that evaluated RFED by comparing it to Walking-in-Place (WIP) and Joystick (JS) interfaces. The RFED system is composed of two major components, redirection and distractors. This paper discusses design challenges, implementation details, and lessons learned during the development of two working RFED systems. The evaluation study examined the effect of the locomotion interface on users' cognitive performance on navigation and wayfinding measures. The results suggest that participants using RFED were significantly better at navigating and wayfinding through virtual mazes than participants using walking-in-place and joystick interfaces. Participants traveled shorter distances, made fewer wrong turns, pointed to hidden targets more accurately and more quickly, and were able to place and label targets on maps more accurately, and more accurately estimate the virtual environment size.

In recent years many advances have enabled users to naturally navigate large-scale graphical worlds. The entertainment industry is increasingly providing visual and body-based cues to users to increase the natural feel of their navigational experience. So far, however, none of the existing solutions fully support the most natural locomotion through virtual worlds. Techniques and technologies which have the advantage of insights into human perceptual sensitivity thus have to be considered. In this context, by far the most natural way to move through the real world is via a full body experience where we receive sensory stimulation to all of our senses, i.e. when walking, running, biking or driving. With some exciting technological advances, people are now beginning to get this same full body sensory experience when navigating computer-generated, three-dimensional environments. Enabling an active and dynamic ability to navigate large-scale virtual scenes is of great interest for many 3D applications demanding locomotion, such as video games, edutainment, simulation, rehabilitation, military, tourism or architecture. Today it is still mostly impossible to freely move through computer generated environments in exactly the same way as the real world. Unnatural and artificial approaches are instead applied, providing only the visual sensation of self-motion. Computer graphics environments were initially restricted to visual displays combined with interaction devices - for example the joystick or mouse - providing often unnatural inputs to generate self-motion. Today, more and more interaction devices like Nintendo Wii, Microsoft Kinect or Sony EyeToy enable intuitive and natural interaction. In this context many research groups are investigating natural, multimodal methods of generating self-motion in virtual worlds based on such consumer hardware.

We report on a user study evaluating Redirected Free Exploration with Distractors (RFED), a large-scale, real-walking, locomotion interface, by comparing it to Walking-in-Place (WIP) and Joystick (JS), two common locomotion interfaces. The between-subjects study compared navigation ability in RFED, WIP, and JS interfaces in VEs that are more than two times the dimensions of the tracked space. The interfaces were evaluated based on navigation and wayfinding metrics and results suggest that participants using RFED were significantly better at navigating and wayfinding through virtual mazes than participants using walking-in-place and joystick interfaces. Participants traveled shorter distances, made fewer wrong turns, pointed to hidden targets more accurately and more quickly, and were able to place and label targets on maps more accurately. Moreover, RFED participants were able to more accurately estimate VE size.

We present a new method for evaluating user experience in interactions with virtual humans (VHs). We code the conversational errors made by the VH. These errors, in addition to the duration of the interaction and the numbers of statements made by the participant and the VH, provide objective, quantitative data about the virtual social interaction. We applied this method to a set of previously collected interactions between medical students and VH patients and present preliminary results. The error metrics do not correlate with traditional measures of the quality of a virtual experience, e.g. presence and copresence questionnaires. The error metrics were significantly correlated with scores on the Maastricht Assessment of Simulated Patients (MaSP), a scenario-appropriate measure of simulation quality, suggesting further investigation is warranted.

Summary form only given. Walking is perhaps the most fundamental example of user interaction with a virtual environment (VE). Making walking, a sensory-motor action, seem natural to the VE user is a problem with many facets: locomotion interfaces should properly stimulate the senses, they should enable movement in any direction, e.g., walking backwards), and they should not impair the user's ability to build a mental model of the scene. Evaluating common locomotion techniques using path analysis and task performance has revealed their relative strengths and weaknesses. I will discuss three threads of recent research in locomotion: increasing the realism of eye position movement (and resulting optical flow), techniques that enable VE users in head-worn-display to really walk around scenes that are larger than the active area of their head tracker, and investigations of the effects of various locomotion interfaces on the cognitive aspects of locomotion.

Users in virtual environments often find navigation more difficult than in the real world. Our new locomotion interface, Improved Redirection with Distractors (IRD), enables users to walk in larger-than-tracked space VEs without predefined waypoints. We compared IRD to the current best interface, really walking, by conducting a user study measuring navigational ability. Our results show that IRD users can really walk through VEs that are larger than the tracked space and can point to targets and complete maps of VEs no worse than when really walking.

Many Virtual Environments require walking interfaces to explore virtual worlds much larger than available real-world tracked space. We present a model for generating virtual locomotion speeds from Walking-In-Place (WIP) inputs based on walking biomechanics. By employing gait principles, our model - called Gait-Understanding-Driven Walking-In-Place (GUD WIP) - creates output speeds which better match those evident in Real Walking, and which better respond to variations in step frequency, including realistic starting and stopping. The speeds output by our implementation demonstrate considerably less within-step fluctuation than a good current WIP system - Low-Latency, Continuous-Motion (LLCM) WIP - while still remaining responsive to changes in user input. We compared resulting speeds from Real Walking, GUD WIP, and LLCM-WIP via user study: The average output speeds for Real Walking and GUD WIP respond consistently with changing step frequency - LLCM-WIP is far less consistent. GUD WIP produces output speeds that are more locally consistent (smooth) and step-frequency-to-walk-speed consistent than LLCM-WIP.

To better understand motion perception in immersive virtual environments, we conducted a user study to quantify perception of scene motion as subjects yawed their heads. We measured psychometric functions of scene-velocity thresholds for different head motions and then extracted 75% thresholds, creating scene-velocity thresholds as functions of three measures of head motion: 1) Angular Range, 2) Peak Angular Velocity, 3) and Peak Angular Acceleration. We also measured scene-velocity thresholds for four phases of head motion: 1) the Start of the head turn, 2) the Center of the head turn, 3) the End of the head turn, 4) and All of the head turn. Scene-velocity thresholds increased as head motion increased for all tested conditions.

As users of head-tracked head-mounted display systems move their heads, latency causes unnatural scene motion. We 1) analyzed scene motion due to latency and head motion, 2) developed a mathematical model relating latency, head motion, scene motion, and perception thresholds, 3) developed procedures to determine perceptual thresholds of scene-velocity and latency without the need for a head-mounted display or a low-latency system, and 4), for six subjects under a specific set of conditions, we measured scene-velocity and latency thresholds, and compared the relationship between these thresholds. Resulting PSEs and JNDs of latency thresholds are in the same range of Ellis and Adelstein. The results are a step toward enabling scientists and engineers to determine latency requirements before building immersive virtual environments using head-mounted display systems.

Virtual Environments (VEs) that use a real-walking locomotion interface have typically been restricted in size to the area of the tracked lab space. Techniques proposed to lift this size constraint, enabling real walking in VEs that are larger than the tracked lab space, all require reorientation techniques (ROTs) in the worst-case situation-when a user is close to walking out of the tracked space. We propose a new ROT using visual and audial distractors-objects in the VE that the user focuses on while the VE rotates-and compare our method to current ROTs through three user studies. ROTs using distractors were preferred and ranked more natural by users. Our findings also suggest that improving visual realism and adding sound increased a user's feeling of presence. Users were also less aware of the rotating VE when ROTs with distractors were used. Our findings also suggest that improving visual realism and adding sound increased a user's feeling of presence.

Virtual environments (VEs) that use a real-walking locomotion interface have typically been restricted in size to the area of the tracked lab space. Techniques proposed to lift this size constraint, enabling real walking in VEs that are larger than the tracked lab space, all require reorientation techniques (ROTs) in the worst-case situation–when a user is close to walking out of the tracked space. We propose a new ROT using distractors–objects in the VE for the user to focus on while the VE rotates –and compare our method to current ROTs through two user studies. Our findings show ROTs using distractors were preferred and ranked more natural by users. Users were also less aware of the rotating VE, when ROTs with distractors were used.

When a virtual environment system prevents a user's avatar hand from penetrating virtual objects, the seen and felt positions of the hand separate. We propose a new method for reducing this position discrepancy as quickly as possible without introducing perceptible discrepancy between the seen and felt motion of the user's hand. We performed a user study to compare this new method to two previous methods of dealing with position discrepancy. Our method showed statistically significant improvements in user-reported naturalness and user preference and showed no loss in user performance

We present a system that enables, for the first time, effective transatlantic cooperative haptic manipulation of objects whose motion is computed using a physically-based model. We propose a technique for maintaining synchrony between simulations in a peer-to-peer system, while providing responsive direct manipulation for all users. The effectiveness of this approach is determined through extensive user trials involving concurrent haptic manipulation of a shared object. A CAD assembly task, using physically-based motion simulation and haptic feedback, was carried out between the USA and the UK with network latencies in the order of 120ms. We compare the effects of latency on synchrony between peers over the Internet with a low latency (0.5ms) local area network. Both quantitatively and qualitatively, when using our technique, the performance achieved over the Internet is comparable to that on a LAN. As such, this technique constitutes a significant step forward for distributed haptic collaboration

Virtual reality (VR) and augmented reality (AR) systems are reaching sufficient maturity that some systems are being used on a regular basis by users and others are close to implementation. There are limitations, however, that have prevented many systems from being truly useful for users. An important limitation is the lack of understanding of human factors issues, such as human perceptual and cognitive limitations, that affect the potential utility of VR or AR systems.

Figure 1. A participant who believes he is aiming at the virtual game board directly in front of him. Without force feedback, a head-mounted display user's avatar may penetrate virtual objects. Some virtual environment designers prevent visual interpenetration, making the assumption that prevention improves user experience. However, preventing visual avatar interpenetration causes discrepancy between visual and proprioceptive cues. We investigated users ’ detection thresholds for visual interpenetration (the depth at which they see that two objects have interpenetrated) and sensory discrepancy (the displacement at which they notice mismatched visual and proprioceptive cues). We found that users are much less sensitive to visual-proprioceptive conflict than they are to visual interpenetration. We present our plan for using this result to create a better technique for dealing with virtual object penetration.

To compare and evaluate locomotion interfaces for users who are (virtually) moving on foot in VEs, we performed a study to characterize task behavior and task performance with different visual and locomotion interfaces. In both a computer-generated environment and a corresponding real environment, study participants walked to targets on walls and stopped as close to them as they could without making contact. In each of five experimental conditions participants used a combination of one of three locomotion interfaces (really walking, walking-in-place, and joystick flying), and one of three visual conditions (head-mounted display, unrestricted natural vision, or field-of-view-restricted natural vision). We identified metrics and collected data that captured task performance and the underlying kinematics of the task. Our results show: 1) Over 95% of the variance in simple motion paths is captured in three critical values: peak velocity; when, in the course of a motion, the peak velocity occurs; and peak deceleration. 2) Correlations of those critical value data for the conditions taken pairwise suggest a coarse ordering of locomotion interfaces by 3) Task performance varies with interface condition, but correlations of that value for conditions taken pairwise do not cluster by naturalness. 4) The perceptual variable, r (also known as the time-to-contact) calculated at the point of peak deceleration has higher correlation with task performance than r calculated at peak velocity.

We present algorithms that enable virtual objects to interact with and respond to virtual representations, avatars, of real objects. These techniques allow dynamic real objects, such as the user, tools, and parts, to be visually and physically incorporated into the virtual environment (VE). The system uses image-based object reconstruction and a volume query mechanism to detect collisions and to determine plausible collision responses between virtual objects and the avatars. This allows our system to provide the user natural interactions with the VE.We have begun a collaboration with NASA Langley Research Center to apply the hybrid environment system to a satellite payload assembly verification task. In an informal case study, NASA LaRC payload designers and engineers conducted common assembly tasks on payload models. The results suggest that hybrid environments could provide significant advantages for assembly verification and layout evaluation tasks.

We designed, developed, deployed, and evaluated the Collaborative nanoManipulator (CnM), a system supporting remote collaboration between users of the nanoManipulator interface to atomic force microscopes. To be accepted by users, the shared nanoManipulator application had to have the same high level of interactivity as the single user system and the application had to support a user's ability to interleave working privately and working collaboratively. The paper describes the entire collaboration system, but focuses on the shared nanoManipulator application. Based on our experience developing the CnM, we present: a method of analyzing applications to characterize the requirements for sharing data between collaborating sites, examples of data structures that support collaboration, and guidelines for selecting appropriate synchronization and concurrency control schemes.

Immersive virtual environments (VEs) provide participants with computer-generated environments filled with virtual objects to assist in learning, training, and practicing dangerous and/or expensive tasks. But for certain tasks, does having every object being virtual inhibit the interactivity? Further, does the virtual object's visual fidelity affect performance? Overall VE effectiveness may be reduced if users spend most of their time and cognitive capacity learning how to interact and adapting to interacting with a purely virtual environment. We investigated how handling real objects and how self-avatar visual fidelity affects performance on a spatial cognitive task in an immersive VE. We compared participants' performance on a block arrangement task in both a real-space environment and several virtual and hybrid environments. The results showed that manipulating real objects in a VE brings task performance closer to that of real space, compared to manipulating virtual objects.

Previous research has shown that even low end-to-end latency can have adverse effects on performance in virtual environments (VE). This paper reports on an experiment investigating the effect of latency on other metrics of VE effectiveness: physiological response, simulator sickness, and self-reported sense of presence. The VE used in the study includes two rooms: the first is normal and non-threatening; the second is designed to evoke a fear/stress response. Participants were assigned to either a low latency (/spl sim/50 ms) or high latency (/spl sim/90 ms) group. Participants in the low latency condition had a higher self-reported sense of presence and a statistically higher change in heart rate between the two rooms than did those in the high latency condition. There were no significant relationships between latency and simulator sickness.

The evaluation of scientific collaboratories has lagged behind their development. Do the capabilities afforded by collaboratories outweigh their disadvantages? To evaluate a scientific collaboratory system, we conducted a repeated-measures controlled experiment that compared the outcomes and process of scientific work completed by 20 pairs of participants (upper level undergraduate science students) working face-to-face and remotely. We collected scientific outcomes (graded lab reports) to investigate the quality of scientific work, post-questionnaire data to measure the adoptability of the system, and post-interviews to understand the participants' views of doing science under both conditions. We hypothesized that study participants would be less effective, report more difficulty, and be less favorably inclined to adopt the system when collaborating remotely. Contrary to expectations, the quantitative data showed no statistically significant differences with respect to effectiveness and adoption.The qualitative data helped explain this null result: participants reported advantages and disadvantages working under both conditions and developed work-arounds to cope with the perceived disadvantages of collaborating remotely. While the data analysis produced null results, considered as a whole, the analysis leads us to conclude there is positive potential for the development and adoption of scientific collaboratory systems.

No abstract available.

A common measure of the quality or effectiveness of a virtual environment (VE) is the mount of presence it evokes in users. Presence is often defined as the sense of being there in a VE. There has been much debate about the best way to measure presence, and presence researchers need, and have sought, a measure that is reliable, valid, sensitive, and objective. We hypothesized that to the degree that a VE seems real, it would evoke physiological responses similar to those evoked by the corresponding real environment, and that greater presence would evoke a greater response. To examine this, we conducted three experiments, the results of which support the use of physiological reaction as a reliable, valid, sensitive, and objective presence measure. The experiments compared participants' physiological reactions to a non-threatening virtual room and their reactions to a stressful virtual height situation. We found that change in heart rate satisfied our requirements for a measure of presence, change in skin conductance did to a lesser extent, and that change in skin temperature did not. Moreover, the results showed that inclusion of a passive haptic element in the VE significantly increased presence and that for presence evoked: 30FPS > 20FPS > 15FPS.

No abstract available.

We present a system for rendering very complex 3D models at interactive rates.We select a subset of the model as preferred viewpoints and partition the space into virtual cells.Each cell contains near geometry, rendered using levels of detail and visibility culling, and far geometry, rendered as a textured depth mesh.Our system automatically balances the screen-space errors resulting from geometric simplification with those from textureddepth-mesh distortion.We describe our prefetching and data management schemes, both crucial for models significantly larger than available system memory.We have successfully used our system to accelerate walkthroughs of a 13 million triangle model of a large coal-fired power plant and of a 1.7 million triangle architectural model.We demonstrate the walkthrough of a 1.3 GB power plant model with a 140 MB cache footprint.

A study by Slater, et al., [1995] indicated that naive subjects in an immersive virtual environment experience a higher subjective sense of presence when they locomote by walking-in-place (virtual walking) than when they push-button-fly (along the floor plane).We replicated their study, adding real walking as a third condition.Our study confirmed their findings.We also found that real walking is significantly better than both virtual walking and flying in ease (simplicity, straightforwardness, naturalness) as a mode of locomotion.The greatest difference in subjective presence was between flyers and both kinds of walkers.In addition, subjective presence was higher for real walkers than virtual walkers, but the difference was statistically significant only in some models.Follow-on studies show virtual walking can be substantially improved by detecting footfalls with a head accelerometer.As in the Slater study, subjective presence significantly correlated with subjects' degree of association with their virtual bodies (avatars).This, our strongest statistical result, suggests that substantial potential presence gains can be had from tracking all limbs and customizing avatar appearance.An unexpected by-product was that real walking through our enhanced version of Slater's visual-cliff virtual environment (Figure 1) yielded a strikingly compelling virtual experience-the strongest we and most of our visitors have yet experienced.The most needed system improvement is the substitution of wireless technology for all links to the user.

We present a real-time stereoscopic video-see-through augmented reality (AR) system applied to the medical procedure known as ultrasound-guided needle biopsy of the breast.The AR system was used by a physician during procedures on breast models and during non-invasive examinations of human subjects.The system merges rendered live ultrasound data and geometric elements with stereo images of the patient acquired through head-mounted video cameras and presents these merged images to the physician in a head-mounted display.The physician sees a volume visualization of the ultrasound data directly under the ultrasound probe, properly registered within the patient and with the biopsy needle.Using this system, a physician successfully guided a needle into an artificial tumor within a training phantom of a human breast.We discuss the construction of the AR system and the issues and decisions which led to the system architecture and the design of the video see-through head-mounted display.We designed methods to properly resolve occlusion of the real and synthetic image elements.We developed techniques for realtime volume visualization of time-and position-varying ultrasound data.We devised a hybrid tracking system which achieves improved registration of synthetic and real imagery and we improved on previous techniques for calibration of a magnetic tracker.

We present a method for producing real-time volume visualizations of continuously captured, arbitrarily-oriented 2D arrays (slices) of data. Our system constructs a 3D representation on-the-fly from incoming 2D ultrasound slices by modeling and rendering the slices as planar polygons with translucent surface textures. We use binary space partition (BSP) tree data structures to provide non-intersecting, visibility-ordered primitives for accurate opacity accumulation images. New in our system is a method of using parallel, time-shifted BSP trees to efficiently manage the continuously captured ultrasound data and to decrease the variability in image generation time between output frames. This technique is employed in a functioning real-time augmented reality system that a physician has used to examine human patients prior to breast biopsy procedures. We expect the technique can be used for real-time visualization of any 2D data being collected from a tracked sensor moving along an arbitrary path.