Regis Kopper

Studying the Effects of Stereo, Head Tracking, and Field of Regard on a Small-Scale Spatial Judgment Task

Spatial judgments are important for many real-world tasks in engineering and scientific visualization. While existing research provides evidence that higher levels of display and interaction fidelity in virtual reality systems offer advantages for spatial understanding, few investigations have focused on small-scale spatial judgments or employed experimental tasks similar to those used in real-world applications. After an earlier study that considered a broad analysis of various spatial understanding tasks, we present the results of a follow-up study focusing on small-scale spatial judgments. In this research, we independently controlled field of regard, stereoscopy, and head-tracked rendering to study their effects on the performance of a task involving precise spatial inspections of complex 3D structures. Measuring time and errors, we asked participants to distinguish between structural gaps and intersections between components of 3D models designed to be similar to real underground cave systems. The overall results suggest that the addition of the higher fidelity system features support performance improvements in making small-scale spatial judgments. Through analyses of the effects of individual system components, the experiment shows that participants made significantly fewer errors with either an increased field of regard or with the addition of head-tracked rendering. The results also indicate that participants performed significantly faster when the system provided the combination of stereo and head-tracked rendering.

Rapid and accurate 3D selection by progressive refinement

Issues such as hand and tracker jitter negatively affect user performance with the ray-casting selection technique in 3D environments. This makes it difficult for users to perform tasks that require them to select objects that have a small visible area, since small targets require high levels of precision. We introduce an approach to address this issue that uses progressive refinement of the set of selectable objects to reduce the required precision of the task. We present a design space of progressive refinement techniques and an exemplar technique called Sphere-casting refined by QUAD-menu (SQUAD). We explore the tradeoffs between progressive refinement and immediate selection techniques in an evaluation comparing SQUAD to ray-casting. Both an analytical evaluation based on a distal pointing model and an empirical evaluation demonstrate that progressive refinement selection can be better than immediate selection. SQUAD was much more accurate than ray-casting, and SQUAD was faster than ray-casting with small targets and less cluttered environments.

Design and Evaluation of Navigation Techniques for Multiscale Virtual Environments

The design of virtual environments for applications that have several levels of scale has not been deeply addressed. In particular, navigation in such environments is a significant problem. This paper describes the design and evaluation of two navigation techniques for multiscale virtual environments (MSVEs). Issues such as spatial orientation and understanding were addressed in the design process of the navigation techniques. The evaluation of the techniques was done with two experimental and two control groups. The results show that the techniques we designed were significantly better than the control conditions with respect to the time for task completion and accuracy.

Effects of Field of View and Visual Complexity on Virtual Reality Training Effectiveness for a Visual Scanning Task

Virtual reality training systems are commonly used in a variety of domains, and it is important to understand how the realism of a training simulation influences training effectiveness. We conducted a controlled experiment to test the effects of display and scenario properties on training effectiveness for a visual scanning task in a simulated urban environment. The experiment varied the levels of field of view and visual complexity during a training phase and then evaluated scanning performance with the simulators highest levels of fidelity and scene complexity. To assess scanning performance, we measured target detection and adherence to a prescribed strategy. The results show that both field of view and visual complexity significantly affected target detection during training; higher field of view led to better performance and higher visual complexity worsened performance. Additionally, adherence to the prescribed visual scanning strategy during assessment was best when the level of visual complexity during training matched that of the assessment conditions, providing evidence that similar visual complexity was important for learning the technique. The results also demonstrate that task performance during training was not always a sufficient measure of mastery of an instructed technique. That is, if learning a prescribed strategy or skill is the goal of a training exercise, performance in a simulation may not be an appropriate indicator of effectiveness outside of training-evaluation in a more realistic setting may be necessary.

Exploring agent physicality and social presence for medical team training

Mixed reality and 3D user interface technologies have increased the immersion, presence, and physicality of user interactions. These technologies can also increase the physicality of embodied conversational agents (ECAs) by making the ECAs occupy and interact with the physical space. We propose that increasing the physicality of an ECA can increase the ECAs social presence, that is, the feeling that the ECA is a real person. In this paper, we examine existing research and formalize the idea of ECA physicality. We also explored the relationship between physicality and social presence by conducting two user studies (n 18 and n 29). Both user studies took place in a medical team training context and involved virtual human ECAs as fellow team members. The first studys results suggested that increasing physicality increased social presence and elicited more realistic behavior. The second studys results suggested that individual dimensions of physicality affect social presence to different extents.

Design and evaluation of 3D selection techniques based on progressive refinement

Issues such as hand and tracker jitter negatively affect user performance with 3D selection techniques based on the ray-casting metaphor. This makes it difficult for users to select objects that have a small visible area, since small targets require high levels of precision. We introduce an approach to address this issue that uses progressive refinement of the set of selectable objects to reduce the required precision of the task. We present three exemplar techniques (sphere-casting refined by QUAD menu (SQUAD), discrete zoom, and continuous zoom) and derive a preliminary design space for progressive refinement from their characteristics. We explore the trade-offs between progressive refinement and immediate selection techniques in two studies: first comparing SQUAD to ray-casting; and second comparing the zooming techniques to ray-casting. In both studies, an analytical evaluation based on a distal pointing model and an empirical evaluation demonstrates that progressive refinement selection can provide significant benefits compared to immediate techniques. In the first study, SQUAD was much more accurate than ray-casting, and SQUAD was faster than ray-casting with small targets and less cluttered environments. The issue with SQUAD, however, is that it requires all selectable objects to be visually distinct. The zooming techniques address this issue by exploring other areas of the progressive refinement design space. They allow users to use the spatial relationships among objects as criteria for selection and to increase precision without requiring precision in pointing. The results of the second study show that while the zooming techniques were significantly slower than ray-casting, accuracy was much higher. Additionally, depending on the size of the target, users chose not to use zoom and, therefore, performed as fast as with ray-casting.

Higher levels of immersion improve procedure memorization performance

Researchers have proposed that immersion could have advantages for tasks involving abstract mental activities, such as conceptual learning; however, there are few empirical results that support this idea. We hypothesized that higher levels of immersion would benefit such tasks if the mental activity can be mapped to objects or locations in a 3D environment. To investigate this hypothesis, we performed an experiment in which participants memorized procedures in a virtual environment and then attempted to recall those procedures. We aimed to understand the effects of three components of immersion on performance. Results demonstrate that a matched software field of view (SFOV), a higher physical FOV, and a higher field of regard (FOR) all contributed to more effective memorization. The best performance was achieved with a matched SFOV and either a high FOV or a high FOR, or both. In addition, our experiment demonstrated that memorization in a virtual environment could be transferred to the real world. The results suggest that, for procedure memorization tasks, increasing the level of immersion even to moderate levels, such as those found in head-mounted displays (HMDs) and display walls, can improve performance significantly compared to lower levels of immersion.

Leveraging Virtual Humans to Effectively Prepare Learners for Stressful Interpersonal Experiences

Stressful interpersonal experiences can be difficult to prepare for. Virtual humans may be leveraged to allow learners to safely gain exposure to stressful interpersonal experiences. In this paper we present a between-subjects study exploring how the presence of a virtual human affected learners while practicing a stressful interpersonal experience. Twenty-six fourth-year medical students practiced performing a prostate exam on a prostate exam simulator. Participants in the experimental condition examined a simulator augmented with a virtual human. Other participants examined a standard unaugmented simulator. Participants reactions were assessed using self-reported, behavioral, and physiological metrics. Participants who examined the virtual human experienced significantly more stress, measured via skin conductance. Participants stress was correlated with previous experience performing real prostate exams; participants who had performed more real prostate exams were more likely to experience stress while examining the virtual human. Participants who examined the virtual human showed signs of greater engagement; non-stressed participants performed better prostate exams while stressed participants treated the virtual human more realistically. Results indicated that stress evoked by virtual humans is linked to similar previous real-world stressful experiences, implying that learners real-world experience must be taken into account when using virtual humans to prepare them for stressful interpersonal experiences.

Comparison of interactive environments for the archaeological exploration of 3D landscape data

The increasingly widespread availability of high-accuracy terrain models is revolutionizing our understanding of historic landscapes across the globe, yet much of this inherently 3D data is viewed and analyzed using 2D Geographical Information System (GIS). The ability to explore the environments in a more immersive way that takes advantage of the full data content is advantageous for professionals and researchers, but is also highly desirable for education and public outreach. This paper describes the method and outcomes of a comparison of three virtual environments; a six-sided CAVE-type immersive virtual reality system (referred to henceforth as CAVE); a 3D web application and a standard 2D desktop paradigm in the form of a GIS. Two groups of participants were used to reflect specialist and non-specialist interests. This study showed that while the 2D GIS, the most common interface for exploring archaeological data, is well-suited to expert interpretation (based on previous familiarity with the system), it is significantly harder for non-specialists to undertake a feature identification and location task in this environment when compared with the 3D environments. Specialist users also mostly preferred the ability to view terrain data in 3D. The experience of fully-immersive CAVE-type system was valuable for a sense of place and contextualizing features in a way that was not possible in the other environments. However it was not shown that this led to improved archaeological observations during the exploration and there is some evidence that the lack of orientation made recounting features in the reflection time more difficult. Although small-scale the experiment gave valuable insight into the use of the different environments by specialist and non-specialist groups, allowing the 3D web application to be identified as the optimal environment for pedagogical purposes.

Exploring the effects of image persistence in low frame rate virtual environments

In virtual reality applications, there is an aim to provide real time graphics which run at high refresh rates. However, there are many situations in which this is not possible due to simulation or rendering issues. When running at low frame rates, several aspects of the user experience are affected. For example, each frame is displayed for an extended period of time, causing a high persistence image artifact. The effect of this artifact is that movement may lose continuity, and the image jumps from one frame to another. In this paper, we discuss our initial exploration of the effects of high persistence frames caused by low refresh rates and compare it to high frame rates and to a technique we developed to mitigate the effects of low frame rates. In this technique, the low frame rate simulation images are displayed with low persistence by blanking out the display during the extra time such image would be displayed. In order to isolate the visual effects, we constructed a simulator for low and high persistence displays that does not affect input latency. A controlled user study comparing the three conditions for the tasks of 3D selection and navigation was conducted. Results indicate that the low persistence display technique may not negatively impact user experience or performance as compared to the high persistence case. Directions for future work on the use of low persistence displays for low frame rate situations are discussed.