VIRTUALNOMICS
Newsletter of the Virtual Environments Technical Group of the Human Factors and Ergonomics Society
Volume 2, Number 1, May, 1996
The Virtual Environments Technical Group is concerned with human factors issues associated with human-virtual environment interaction. These issues include maximizing human performance efficiency in virtual environments, minimimizing health and safety problems, and circumventing potential social issues through proactive assessment. To be placed on our mailing list send your email address to:
mourant@coe.neu.edu
Contact the Human Factors and Ergonomics Society (above) for information on joining the VETG. 1. 40th Annual Meeting
2. Surface Texture at Near Distances
3. The Effects of Symbolic Enhancements and Geometric Field of View on the Perceptions of Space in a Desktop Virtual Environment
4. Assessing the Impact of Control and Sensory Compatibility on Sickness in Virtual Environments
5. Development of Methods to Quantify the Visual Stimulus for Cybersickness
6. An Initial Evaluation of a Direct Vestibular Display in a Virtual Environment
7. Effect of Visual Display Parameters on Driving Performance in a Virtual Environments Driving Simulator
8. Impact of Varying Levels of Autostereovision Upon Telemanipulation
9. Exploring the Influence of a Virtual Body on Spatial Awareness
Posters
10. Usability Evaluation of Low-End Virtual Reality Systems
11. Virtual Reality Theraphy: An Innovative Modality for the Treatment of Psychological Disorders
12. Simulator Sickness in Stereoscopic Helmet-Mounted Displays
13. Tracking Control in Forming Spatial Representations From Virtual Reality Environments
14. A Note From the Chair
40th Annual Meeting
The Human Factors and Ergonomics Society will hold its 40th Annual Meeting between September 2-6, 1996 in Philadelphi, Pennsylvania. Below are the abstracts of papers sponsored by the Virtual Environments Technical Group.
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VETG SESSION 1:
Tuesday, September3, 1996 10 A.M.
SURFACE TEXTURE AT NEAR DISTANCES
by Paul Kline and Bob Witmer email: klinep@stricom.army.mil
This study investigated the effects of three system related cues on estimates of near distances. Subjects (N=28) viewed a simple VE and used a magnitude estimation procedure to generate distance estimates to a wall at the end of a corridor 1 to 12 feet away. Independent variables included type of wall texture pattern (2 levels), resolution of wall pattern (2 levels), display FOV (2 levels), and distance (12 levels). Dependent variables included distance estimation, response latency, and relative error. Subjects consistently underestimated distances judged using a wide FOV and overestimated distances judged with a narrow FOV. Distance estimates were significantly affected by both FOV and texture pattern. Significant interactions of distance with FOV, resolution, and pattern revealed that these variables had greater effects at the closer distances. The most accurate estimates occurred with a wide FOV and a rich, fine resolution pattern.
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THE EFFECTS OF SYMBOLIC ENHANCEMENTS AND GEOMETRIC
FIELD OF VIEW ON THE PERCEPTIONS OF SPACE IN A DESKTOP
VIRTUAL ENVIRONMENT
by Dennis Neale email: dnealE@vt.edu
This study investigated perceptual and cognitive issues relating to manipulations of geometric field of view
(GFOV) in three-dimensional (3D) perspective displays and the effects of incorporating virtual environment (VE) enhancements in the interface based on visual momentum (VM) techniques. Sixty participants, who were
pretested for spatial ability, were required to navigate through a virtual office building while estimating space dimensions and performing spatial orientation tasks. A 3 x 2 x 2 mixed-subjects design compared three levels of GFOV, two levels of VM, and two levels of Difficulty. This study effectively demonstrates that the spatial characteristics of architectural representations in perspective displays are not always accurately perceived. As spatial ability increased, the ability to accurately estimate space dimensions also increased. Furthermore, the results indicate that manipulations in GFOV can produce perceptual and cognitive errors for the basic space dimensions in perspective displays; however, VM can be used to compensate for many of the biases shown to occur.
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ASSESSING THE IMPACT OF CONTROL AND SENSORY COMPATIBILITY
ON SICKNESS IN VIRTUAL ENVIRONMENTS
Virtual reality (VR) users are frequently limited by motion sickness like symptoms. One factor that might influence sickness in VR is the level of control one has in the virtual environment. Reason+s Sensory Conflict Theory suggested that motion sickness occurs when incompatibilities exist between sensory inputs. It is possible that control and sensory compatibility are positively related. If this is the case, increasing control in a virtual environment should result in decreasing symptomology. To test this, the present study used the Simulator Sickness Questionnaire to measure symptomology of 163 participants after exposure to a virtual environment. Three levels of control and compatibility were assessed. It was hypothesized that the participants with control and compatible sensory information would experience fewer symptoms than participants in either the
control/incompatible or no control/incompatible conditions. Although significant main effects were found for both gender and condition, the findings were opposite of those hypothesized. Possible explanations for these findings are discussed.
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DEVELOPMENT OF METHODS TO QUANTIFY THE VISUAL STIMULUS
FOR CYBERSICKNESS
by Robert S. Kennedy, Kevin S. Berbaum, William P. Dunlap, and Larry Hettinger
Simulator sickness is a significant human factors issue in simulator and virtual environment systems. The extent that users are affected by sickness-inducing stimuli in virtual environments may hinder the behavioral goals sought (training, systems evaluation, etc.). To alleviate the problem, it is first necessary to accurately and reliably quantify the amount and type of visual motion stimulation that leads to motion sickness-like discomfort. This paper
describes a human performance-based approach to the development of a system capable of measuring the visual stimulus for motion sickness. Military flight simulator trainees reported their severity levels of sickness. A video captured a significant portion of their visual scene and a PC-mounted, frame-grabber algorithm was used to score their flight video records. Results show a significant positive correlation between roll motion and overall sickness. Development of these and another method to quantify the visual stimulus for cybersickness are discussed.
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VETG SESSION 2: VISUAL AND VESTIBULAR DISPLAYS IN VIRTUAL
ENVIRONMENTS
Tuesday, September 3, 1996, 1:00pm
AN INITIAL EVALUATION OF A DIRECT VESTIBULAR DISPLAY IN A
VIRTUAL ENVIRONMENT
by Jeffrey D. Cress, Lawrence J. Hettinger, James A. Cunningham, Gary E. Riccio, Grant R. McMillan and Michael W. Haas
The US Air Force Armstrong Laboratory+s Human Interface Technology Branch is currently investigating the development and potential application of direct vestibular displays. The Electrical Vestibular Stimulus (EVS) technology described in this paper uses electrodes located behind the ears to deliver a low-level electrical current
in the area of the eighth cranial nerve of the central nervous system to produce a compelling sensation of roll motion about the body's fore-aft axis. In this study, subjects experienced the EVS display while simultaneously observing a large field-of-view visual roll display, and were asked to rate various aspects of quality and
magnitude of self-motion. The two displays were driven in a sinusoidal fashion at various phase relationships relative to one another. Results revealed that the fidelity of the motion experience depended upon the phase relationship between the two displays. Results also indicated that when an appropriate phase relationship was used, the vestibular display significantly improved the fidelity of the motion experience when compared to a visual-only display.
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EFFECT OF VISUAL DISPLAY PARAMETERS ON DRIVING
PERFORMANCE IN A VIRTUAL ENVIRONMENTS DRIVING SIMULATOR
by Oren H. Levine and Ronald R. Mourant email: ohl@world.std.com mourant@coe.neu.edu
In virtual environment applications, there is a tradeoff between the quality of the graphic image and the speed at which the application runs. In driving simulation, the content and quality of the visual image are particularly important, which suggests that there are limits to the degree they can be reduced. A virtual environments driving simulator was used to investigate the effects of visual display parameters on driver performance and perception. A road tracking study compared two display devices, two rendering algorithms, and three levels of road side delineation poles. Subjects drove the simulator through a series or road courses and answered questionnaires designed to evaluate their perception of the realism of the simulator and the sense of immersion in the virtual environment. The results of the study confirm previous work on the beneficial effects of road side delineation poles on driving performance. They also suggest the importance of lag in the perception of driving performance and immersion, and the importance of shaded images in actual driving task performance.
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IMPACT OF VARYING LEVELS OF AUTOSTEREOVISION UPON
TELEMANIPULATION
by Steven F. Wiker, Daniel R. Baker, Steven R. Ardnt, and Weijia Zou email: swiker@dehpost.sphcm.washington.edu
Use of an autostereovision display system produced material improvements in positioning movement capacity of a position-controlled master-slave telemanipulator. Operators reported greater controllability of the
telemanipulator with introduction of binocular stereoacuity. Hyperstereo (i.e., remote camera separation equal to twice the operator+s Interpupilary distance) produced further improvement in remote positioning capacity. But did so at the expense of reduced operator acceptance and perceived controllability. Performance benefits observed with the introduction of the autostereo display were found regardless of variations in remote site illumination (65 to 196 lux).
EXPLORING THE INFLUENCE OF A VIRTUAL BODY ON SPATIAL
AWARENESS
by Mark H. Draper, Maxwell Wells, Valerie Gawron, Thomas Furness
A virtual reality study explored the potential for a virtual body (VB) to enhance a participant's spatial awareness of a virtual environment (VE) by providing an invariant, subtle point of reference for object positioning. The study used the ecological metric of perceived reachability as the manifestation of spatial awareness. Nine subjects entered a VE and performed a maximum virtual-reach estimation task in which VB configuration (full-body, hand-only, no-body) and target height (low, medium, high) were manipulated. Estimations of reach were more accurate for low target heights. This finding seemed most attributable to the influence of the more richly patterned visual background for that condition. A complex interaction between VB configuration and target height indicates that the specific VB used may impact observed performance. Subjective comments also indicate a perceived utility of a full-body virtual body. Results are discussed in regard to potential design implications and future research opportunities.
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VETG POSTERS
USABILITY EVALUATION OF LOW-END VIRTUAL REALITY SYSTEMS
by Eric A. Vaden, Jennifer A. Ehrlich, and Eugenia M. Kolasinski email: ehrlichj@stricom.army.mil
Rapid advances in computer technology have combined with decreased costs to make low-end Virtual Reality (VR) systems available for home use. The usability of one such low-end system was assessed. Participants used the system for approximately 20 minutes before providing feedback through a usability survey. Reports of discomfort and heat were associated with the area where the front pad of the HMD rests on the users forehead. Participants also reported discordances, for lag and accuracy, between head movement and visual display dynamics. Significant correlations were found between the ratings of several HMD characteristics and an overall measure of simulator sickness. Ratings of the inability to anticipate what would happen next in response to user actions and ratings of visual acuity for near objects correlated significantly with the total sickness measure. Although these issues are not new, they must be revisited as these systems begin to move from an industrial user base into the home.
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VIRTUAL REALITY THERAPY: AN INNOVATIVE MODALITY FOR THE
TREATMENT OF PSYCHOLOGICAL DISORDERS
Behavioral therapy has included exposing the subject to anxiety producing stimuli. These stimuli are generated through a variety of modalities including imaginal (subject generates stimulus via imagination) and In Vivo (subject experiences the real world). In addition to current imaginal and In Vivo modalities, virtual environments can also generate stimuli that will be utilized in desensitization therapy. Virtual Environment Desensitization (VED) also has the advantage of providing greater control over graded exposure stimulus parameters and the ability to isolate which virtual stimulus parameters are essential in generating a phobic response, as well as greater efficiency and economy in delivering the equivalent of In Vivo exposure within the therapist's office. The subject, who suffered from fear of flying, was a 42-year-old married man. His anxiety and avoidance behavior were interfering with his normal activities. The SUDS, an instrument which measures the degree to which the subject is effected by VED, was administrated every two to five minutes. The apparatus for this study consisted of a stereoscopic head-mounted display, a head tracking device, a virtual reality Pentium-based system and several other interaction devices. A virtual city scene was created from an area with a radius of 40-kilometers and a center which simulated the City of Atlanta available for the subject to observe while flying over the virtual city. The flying was accomplished by a simulated Apache helicopter. A simulated audio (helicopter's engine sound) accompanied the Apache. For a more realistic effect, a vibration apparatus was placed under the physical cockpit. A model of virtual therapist was created and placed on the co-pilot's seat. The virtual therapist scenario allowed the physical world therapist to communicate with the subject in the virtual world. The treatment procedure involved five sessions, which lasted 20 to 30 minutes. The SUDS ratings measured the degree to which the subject was affected by VED. In VED therapy the subject's anxiety usually increased as he was exposed to more challenging situations (e.g., flying over a river or lake),and decreased as the time in that situation was increased. The
symptoms experienced by the subject during VED therapy included sweaty palms, loss of balance, weakness in the knees, etc. These symptoms also appeared in the study which dealt with the subject's treatment for height phobia. Similar to our first reported controlled study to use virtual reality for the treatment of agoraphobia, the results of this case study indicted that VED was effective in reducing self-reported anxiety. At this time the subject can comfortably take a flight. Since the termination of the treatment, has taken several flights to
professional conferences and reported that he had more comfortable feelings and reduced symptoms than those experienced prior to the VED treatment.
ACKNOWLEDGMENT This project is sponsored by Boeing Computer Services, Virtual Systems Division and supported by the U.S. Army Research Laboratory (Contract Number DAAL03-92-6-0377).
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SIMULATOR SICKNESS IN STEREOSCOPIC VS. MONOSCOPIC
HELMET-MOUNTED DISPLAYS
by Jennifer A. Ehrlich and Michael J. Singer email: ehrlichj@stricom.army.mil
A common and constant problem with Virtual Environments (VE) is simulator sickness. Its symptoms are similar to those experienced in motion sickness. In this research we investigated the differential effects of monoscopic and stereoscopic displays as well as head-tracking on the incidence and severity of simulator sickness. To gauge simulator sickness, we used two different measures: the self-report Simulator Sickness Questionnaire (SSQ), and a postural stability measure of ataxic decrements. The data revealed that the stereoscopic condition was more nauseogenic. In addition, post-experimental Disorientation and Oculomotor subscales and the Total Severity measure of the SSQ all correlated significantly with completion time on a task that required more near-far focal
transitions within a short period of time than any of the other tasks.
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TRACKING CONTROL IN FORMING SPATIAL REPRESENTATIONS FROM
VIRTUAL REALITY ENVIRONMENTS
by Benjamin Knott and Marc Sebrechts email: sebrechts@cua.edu
This study investigated the effects of tracking control in virtual reality (VR) environments. Participants learned the spatial layout of a building, viewed through a helmet mounted display by navigating along a specified path in one of three conditions. In +active+ VR the image of the building responded to participants+ rotational movement (e.g., looking right and left). In +cognitive tracking+ participants moved in synchrony with a pre-recorded walkthrough. In +passive+ VR participants were not allowed rotational movement while viewing the walkthrough. To measure accessibility of mental objects, participants were tested on proximity of pairs of objects in the building, using either picture or word stimuli. Reaction time for proximity judgments for all three conditions decreased with inter-object distance along the learned route, suggesting that route distance is a functional characteristic of the resulting spatial mental model. Spatial information was slightly more accessible in passive VR than in active VR or cognitive tracking as indicated by faster reaction times. Finally proximity
judgments were substantially faster for picture stimuli than for words. This is consistent with the dual-code theory of Pavio (1975) suggesting that pictorial stimuli allowed easier access to an image-based mental model.
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A NOTE FROM THE CHAIR
The present officers of the Virtual Environments Technical Group are: Ronald R. Mourant (mourant@coe.neu.edu) Chair
Kay M. Stanney (stanney@iems.engr.ucf.edu) Annual Meeting Program Chair Shumin Zhai (Zhai@cs.utoronto.ca) Webmaster
We need more active members. At the 40th Annual Meeting in Philadelhia we will have the yearly meeting of the VETG. Please bring your ideas and suggestions for improving our technical group. Thank you.
