Artificial Intelligence (AI) and indoor sensing increasingly support decision-making in spatial environments. However, traditional visualization methods impose a substantial mental workload when viewers translate this digital information into real-world spaces, leading to inappropriate reliance on AI. Embedded visualizations in Augmented Reality (AR), by integrating information into physical environments, may reduce this workload and foster more appropriate reliance on AI. To assess this, we conducted an empirical study (N = 32) comparing an AR embedded visualization (X-ray) and 2D Minimap in AI-assisted, time-critical spatial target selection tasks. Surprisingly, evidence shows that the embedded visualization led to greater inappropriate reliance on AI, primarily as over-reliance, due to factors like perceptual challenges, visual proximity illusions, and highly realistic visual representations. Nonetheless, the embedded visualization showed benefits in spatial mapping. We conclude by discussing empirical insights, design implications, and directions for future research on human-AI collaborative decision in AR.

We present a visualization design study of creating a collaborative virtual reality (VR) system for radiation treatment planning, with an emphasis on proton therapy. The goal is to support teams of dosimetrists, physicians, and medical physicists as they review and compare multiple possible patient-specific treatment plans, which requires analyzing complex 3D spatial relationships between a radiation dosage volume and anatomical structures. The approach is a novel combination and refinement of interactive visualization techniques including: networked multi-user immersive visualization, interactive volume rendering and slicing with 3D widgets and gestures, superimposed surface rendering with GPU-accelerated curvature-directed lines, smart cursors, teleporting, and avatars. These features are integrated within a workflow that supports three complementary modes of visual data comparison (juxtaposition, interchangeable, and explicit encoding). Results and feedback from multi-year iterative development with users and a summative field deployment in the form of a mock plan-review meeting reveal several advantages relative to current clinical practice and suggest directions for future work.

Spatiotemporal sensitivity to high frequency information declines with increased peripheral eccentricity. Foveated rendering exploits this by decreasing the spatial resolution of rendered images in peripheral vision, reducing the rendering cost by omitting high frequency details. As foveation levels increase, the rendering quality is reduced, and traditional foveated rendering systems tend not to preserve samples that were previously rendered at high spatial resolution in previous frames. Additionally, prior research has shown that saccade landing positions are distributed around a target location rather than landing at a single point, and that even during fixations, eyes perform small microsaccades around a fixation point. This creates an opportunity for sampling from temporally neighbouring frames with differing foveal locations to reduce the required rendered size of the foveal region while achieving a higher perceived image quality. We further observe that the temporal presentation of pixels frame-to-frame can be viewed as a data stream, presenting a random sampling problem. Following this intuition, we propose a Weighted Reservoir Sampling technique to efficiently maintain a reservoir of the perceptually relevant high quality pixel samples from previous frames and incorporate them into the computation of the current frame. This allows the renderer to render a smaller region of foveal pixels per frame by temporally reusing pixel samples that are still relevant to reconstruct a higher perceived image quality, while allowing for higher levels of foveation. Our method operates on the output of foveated rendering, and runs in under 1 ms at 4K resolution, making it highly efficient and integrable with real-time VR and AR foveated rendering systems.

This paper quantitatively investigates the feasibility of, and merit in, soliciting continuous subjective cybersickness ratings as participants passively engage in an immersive VR experience. The main research questions addressed are: (1) Feasibility: To what extent will participants successfully engage, unprompted, in continuous cybersickness reporting while engaging with a secondary task? and (2) Merit: To what extent do continuously reported subjective cybersickness ratings offer valuable insights beyond what can be obtained from less frequent querying?

Virtual reality (VR) forest bathing for stress relief and mental health has recently become a popular research topic. As people spend more of their lives indoors and have less access to the restorative benefit of nature, having a VR nature supplement has the potential to improve quality of life. However, the optimal design of VR nature environments is an active area of investigation with many research questions to be explored. One major issue with VR is the difficulty of rendering high-fidelity assets in real time without causing cybersickness, or VR motion sickness, within the headset. Due to this limitation, we investigate if the realism of VR nature is critical for the restorative effects by comparing a low-realism nature environment to a high-realism nature environment. We only found a significant difference in the perceived restorativeness of the two environments, but after observing trends in our data toward the stress reduction potential of the high-realism environment, we suggest exploring more varieties of high and low-realism environments in future work to investigate the full potential of VR and how people respond.

Distractions in mixed reality (MR) environments can significantly influence user experience, affecting key factors such as presence, reaction time, cognitive load, and Break in Presence (BIP). Presence measures immersion, reaction time captures user responsiveness, cognitive load reflects mental effort, and BIP represents moments when attention shifts from the virtual to the real world, breaking immersion. While prior work has established that distractions impact these factors individually, the relationship between these constructs remains underexplored, particularly in MR environments where users engage with both real and virtual stimuli. To address this gap, we have presented a theoretical model to understand how congruent and incongruent distractions affect all these constructs. We conducted a within-subject study (N = 54) where participants performed image-sorting tasks under different distraction conditions. Our findings show that incongruent distractions significantly increase cognitive load, slow reaction times, and elevate BIP frequency, with presence mediating these effects.

Virtual reality (VR) could support the need for easily accessible therapeutic techniques, such as viewing art and immersing oneself in nature. Our study searches for the optimal virtual environment (VE) by exploring whether beauty in moving and still VEs contributes to stress reduction and perceived restorativeness. We hypothesized that the moving forest environment would result in the most stress reduction, while the abstract art would result in the least, with additional comparisons to a still forest environment and a control condition. The control condition took place outside the virtual headset to simulate what stress reduction would look like without a nature intervention. After working with 78 participants, we found an increase in statistical significance for stress reduction and perceived restorativeness in the moving forest condition compared to the control, as measured by the Zuckerman Inventory of Personal Reactions (ZIPERS) positive affect and the Perceived Restorativeness Scale (PRS). Additionally, the PRS and heart rate measures showed greater restorativeness in the moving forest condition than in the abstract art condition. Heart rate measures also showed statistical significance between the forest image condition and the control and moving forest conditions.

Measuring presence is critical to improving user involvement and performance in Mixed Reality (MR). Presence, a crucial aspect of MR, is traditionally gauged using subjective questionnaires, leading to a lack of time-varying responses and susceptibility to user bias. Inspired by the existing literature on the relationship between presence and human performance, the proposed methodology systematically measures a user's reaction time to a visual stimulus as they interact within a manipulated MR environment. We explore the user reaction time as a quantity that can be easily measured using the systemic tools available in modern MR devices. We conducted an exploratory study (N = 40) with two experiments designed to alter the users' sense of presence by manipulating place illusion and plausibility illusion. We found a significant correlation between presence scores and reaction times with a correlation coefficient -0.65, suggesting that users with a higher sense of presence responded more swiftly to stimuli. We develop a model that estimates a user's presence level using the reaction time values with high accuracy of up to 80%. While our study suggests that reaction time can be used as a measure of presence, further investigation is needed to improve the accuracy of the model.

A prerequisite to improving the presence of a user in mixed reality (MR) is the ability to measure and quantify presence. Traditionally, subjective questionnaires have been used to assess the level of presence. However, recent studies have shown that presence is correlated with objective and systemic human performance measures such as reaction time. These studies analyze the correlation between presence and reaction time when technical factors such as object realism and plausibility of the object's behavior change. However, additional psychological and physiological human factors can also impact presence. It is unclear if presence can be mapped to and correlated with reaction time when human factors such as conditioning are involved. To answer this question, we conducted an exploratory study ($N=60$) where the relationship between presence and reaction time was assessed under three different conditioning scenarios: control, positive, and negative. We demonstrated that human factors impact presence. We found that presence scores and reaction times are significantly correlated (correlation coefficient of -0.64), suggesting that the impact of human factors on reaction time correlates with its effect on presence. In demonstrating that, our study takes another important step toward using objective and systemic measures like reaction time as a presence measure.

Shinrin-yoku, also known as forest bathing, is a nature immersion practice that has been shown to have restorative effects on mental health. Recently, applications of shinrin-yoku in virtual reality (VR) have been investigated as means of providing similar mental health benefits to people that do not have direct access to nature. These applications have shown similar health benefits, although not to the extent of real nature. The factors that make VR nature immersion effective are little researched to date. This paper investigates the Biophilia Hypothesis in the context of a VR-based nature immersion experience. Twenty-six participants were immersed in a computer-generated virtual natural environment that was either high in biomass (forest) or devoid of biomass (canyon), after experiencing an arithmetic stressor task. We compared multiple restorative outcomes between the high and low biomass groups, as well as preference ratings for real and virtual high and low biomass scenes among all participants. Our results call for further investigation into data trends we observed.

Understanding the extent to which, and conditions under which, scene detail affects spatial perception accuracy can inform the responsible use of sketch-like rendering styles in applications such as immersive architectural design walkthroughs using 3D concept drawings. This paper reports the results of an experiment that provides important new insight into this question using a custom-built, portable video-see-through (VST) conversion of an optical-see-through head-mounted display (HMD). Participants made egocentric distance judgments by blind walking to the perceived location of a real physical target in a real-world outdoor environment under three different conditions of HMD-mediated scene detail reduction: full detail (raw camera view), partial detail (Sobel-filtered camera view), and no detail (complete background subtraction), and in a control condition of unmediated real world viewing through the same HMD. Despite the significant differences in participants' ratings of visual and experiential realism between the three different video-see-through rendering conditions, we found no significant difference in the distances walked between these conditions. Consistent with prior findings, participants underestimated distances to a significantly greater extent in each of the three VST conditions than in the real world condition. The lack of any clear penalty to task performance accuracy not only from the removal of scene detail, but also from the removal of all contextual cues to the target location, suggests that participants may be relying nearly exclusively on context - independent information such as angular declination when performing the blind-walking task. This observation highlights the limitations in using blind walking to the perceived location of a target on the ground to make inferences about people's understanding of the 3D space of the virtual environment surrounding the target. For applications like immersive architectural design, where we seek to verify the equivalence of the 3D spatial understanding derived from virtual immersion and real world experience, additional measures of spatial understanding should be considered.

Current avatar representations used in immersive VR applications lack features that may be important for supporting natural behaviors and effective communication among individuals. This study investigates the impact of the visual and nonverbal cues afforded by three different types of avatar representations in the context of several cooperative tasks. The avatar types we compared are No_Avatar (HMD and controllers only), Scanned_Avatar (wearing an HMD), and Heal_Avatar (video-see-through). The subjective and objective measures we used to assess the quality of interpersonal communication include surveys of social presence, interpersonal trust, communication satisfaction, and attention to behavioral cues, plus two behavioral measures: duration of mutual gaze and number of unique words spoken. We found that participants reported higher levels of trustworthiness in the Real_Avatar condition compared to the Scanned_Avatar and No_Avatar conditions. They also reported a greater level of attentional focus on facial expressions compared to the No_Avatar condition and spent more extended time, for some tasks, attempting to engage in mutual gaze behavior compared to the Scanned_Avatar and No_Avatar conditions. In both the Heal_Avatar and Scanned_Avatar conditions, participants reported higher levels of co-presence compared with the No_Avatar condition. In the Scanned_Avatar condition, compared with the Heal_Avatar and No_Avatar conditions, participants reported higher levels of attention to body posture. Overall, our exit survey revealed that a majority of participants (66.67%) reported a preference for the Real_Avatar, compared with 25.00% for the Scanned_Avatar and 8.33% for the No_Avatar, These findings provide novel insight into how a user's experience in a social VR scenario is affected by the type of avatar representation provided.

Eye height manipulations have previously been found to affect judgments of object size and egocentric distance in both real and immersive virtual environments. In this short paper we report the results of an experiment that explores people’s sensitivity to various offsets of their eye height in VR using a forced-choice task in a wide variety of different architectural models. Our goal is to better understand the range of eye height manipulations that can be surreptitiously employed under different environmental conditions.

Virtual reality applications have begun to offer great potential for communication in recent years. Creating an immersive virtual social environment that simulates a real social environment requires providing users with communication cues such as visual, verbal, and nonverbal cues to increase their sense of inhabiting the virtual world. In this work, we will investigate the influence of avatar representation and behavior on communication in an immersive, multiuser, same-place virtual environment by comparing three conditions of avatar representation: video see-through, scanned realistic avatar, and no-avatar representations. Subjective and objective measurements will be used to describe participants' observations and track their movement behavior to ascertain the effect of avatar representations on communication, based on personal presence, social presence, and trustworthiness.

Immersive virtual reality (VR) technology has the potential to play an important role in the conceptual design process in architecture, if we can ensure that sketch-like structures are able to afford an accurate egocentric appreciation of the scale of the interior space of a preliminary building model. Historically, it has been found that people tend to perceive egocentric distances in head-mounted display (HMD) based virtual environments as being shorter than equivalent distances in the real world. Previous research has shown that in such cases, reducing the quality of the computer graphics does not make the situation significantly worse. However, other research has found that breaking the illusion of reality in a compellingly photorealistic VR experience can have a significant negative impact on distance perception accuracy.

This paper reports preliminary investigations into the extent to which future directional intention might be reliably inferred from head pose and eye gaze during locomotion. Such findings could help inform the more effective implementation of realistic detailed animation for dynamic virtual agents in interactive first-person crowd simulations in VR, as well as the design of more efficient predictive controllers for redirected walking. In three different studies, with a total of 19 participants, we placed people at the base of a T-shaped virtual hallway environment and collected head position, head orientation, and gaze direction data as they set out to perform a hidden target search task across two rooms situated at right angles to the end of the hallway. Subjects wore an nVisorST50 HMD equipped with an Arrington Research ViewPoint eye tracker; positional data were tracked using a 12-camera Vicon MX40 motion capture system. The hidden target search task was used to blind participants to the actual focus of our study, which was to gain insight into how effectively head position, head orientation and gaze direction data might predict people's eventual choice of which room to search first. Our results suggest that eye gaze data does have the potential to provide additional predictive value over the use of 6DOF head tracked data alone, despite the relatively limited field-of-view of the display we used.

We are pleased to present the technical papers for the 2016 IEEE Virtual Reality Conference (IEEE VR 2016), held March 19–23, 2016, in Greenville, South Carolina, USA.

No abstract available.

Welcome to the 21st IEEE Virtual Reality Conference, the premier international conference and exhibition on virtual reality!We are honored to host IEEE VR 2014 in Minneapolis, Minnesota, a vibrant center of culture, business, learning, and research in the upper midwest of the United States.The highlight of our outstanding technical program is the eighteen full-length research papers that are being published as a special issue of the IEEE Transactions on Visualization and Computer Graphics.We are indebted to the TVCG editor-in-chief, Ming Lin, for her vision and leadership in continuing to make this collaboration possible.Complementing these journal papers, our conference proceedings include ten short papers and fortyfour abstracts presenting an exciting collection of groundbreaking technical contributions.We thank this year's program chairs, Sabine Coquillart, Kiyoshi Kiyokawa, J. Edward Swan II, and Doug A. Bowman, for their dedicated leadership in soliciting papers, managing the multi-phase review process, and arranging the paper presentations at the conference.In addition to the long and short paper presentations, the week's technical events include the presentation of three panels, five workshops, three tutorials, thirty-one posters, thirteen research demonstrations, ten exhibits, and eight videos, bookended by keynote and capstone talks from VR visionaries Henry Fuchs and Hunter Hoffman.Accompanying these activities is the second annual Virtual Reality Doctoral Consortium, which with the generous support of the US National Science Foundation is providing a valuable mentoring opportunity to twelve promising PhD students working in the areas of virtual and augmented reality and 3D user interaction.We are further honored to again have the IEEE Symposium on 3D User Interfaces (3DUI) held jointly with the VR conference.The 9th installment of 3DUI features an outstanding program of papers, technotes, posters, and

In this poster, we summarize the results of a user study that investigates the relative extent to which people are able to maintain spatial awareness when exploring a virtual environment using a motorized wheelchair. We asked 24 participants to travel through a 24' wide, circularly symmetric virtual room, searching the contents of 16 randomly positioned and oriented boxes to locate 8 hidden targets, using each of the following four locomotion methods: real walking; virtual translation with real rotation while standing and using a body-worn joystick; real driving in a motorized wheelchair; and virtual translation with real rotation while sitting in a swivel chair with a joystick mounted on one of its arms. We computed four measures of search efficiency: distance travelled, search time, number of targets revisited, and proportion of trials with no revisits. We found that participants performed significantly better, overall, with real walking than with either of the methods that involved virtual translation, while performance with the wheelchair was intermediate. These results confirm that a mobile, motorized wheelchair interface offers some advantages over stationary joystick travel.

Walking is the most natural form of locomotion for humans, and real walking interfaces have demonstrated their benefits for several navigation tasks. With recently proposed redirection techniques it becomes possible to overcome space limitations as imposed by tracking sensors or laboratory setups, and, theoretically, it is now possible to walk through arbitrarily large virtual environments. However, walking as sole locomotion technique has drawbacks, in particular, for long distances, such that even in the real world we tend to support walking with passive or active transportation for longer-distance travel. In this article we show that concepts from the field of redirected walking can be applied to movements with transportation devices. We conducted psychophysical experiments to determine perceptual detection thresholds for redirected driving, and set these in relation to results from redirected walking. We show that redirected walking-and-driving approaches can easily be realized in immersive virtual reality laboratories, e. g., with electric wheelchairs, and show that such systems can combine advantages of real walking in confined spaces with benefits of using vehicle-based self-motion for longer-distance travel.

The articles in this special section contain selected papers from the IEEE Virtual Reality Conference (VR).

Users of IVEs typically underestimate distances during blind walking tasks, even though they are accurate at this task in the real world. The cause of this underestimation is still not known. Our previous work found an exception to this effect: When the virtual environment was a realistic, co-located replica of the concurrently occupied real environment, users did not significantly underestimate distances. However, when the replica was rendered in an NPR style, we found that users underestimated distances. In this study we explore whether the inaccuracy in distance estimation could be due to lack of size and distance cues in our NPR IVE, or if it could be due to a lack of presence. We ran blind walking trials in a new replica IVE that combined features of the previous two IVEs. Participants significantly underestimated distances in this environment.

Non-photorealistically rendered (NPR) immersive virtual environments (IVEs) can facilitate conceptual design in architecture by enabling preliminary design sketches to be previewed and experienced at full scale, from a first-person perspective. However, it is critical to ensure the accurate spatial perception of the represented information, and many studies have shown that people typically underestimate distances in most IVEs, regardless of rendering style. In previous work we have found that while people tend to judge distances more accurately in an IVE that is a high-fidelity replica of their concurrently occupied real environment than in an IVE that it is a photorealistic representation of a real place that they've never been to, significant distance estimation errors re-emerge when the replica environment is represented in a NPR style. We have also previously found that distance estimation accuracy can be improved, in photo-realistically rendered novel virtual environments, when people are given a fully tracked, high fidelity first person avatar self-embodiment. In this paper we report the results of an experiment that seeks to determine whether providing users with a high-fidelity avatar self-embodiment in a NPR virtual replica environment will enable them to perceive the 3D spatial layout of that environment more accurately. We find that users who are given a first person avatar in an NPR replica environment judge distances more accurately than do users who experience the NPR replica room without an embodiment, but not as accurately as users whose distance judgments are made in a photorealistically rendered virtual replica room. Our results provide a partial solution to the problem of facilitating accurate distance perception in NPR virtual environments, while supporting and expanding the scope of previous findings that giving people a realistic avatar self-embodiment in an IVE can help them to interpret what they see through an HMD in a way that is more similar to how they would interpret a corresponding visual stimulus in the real world.

Previous work has shown that giving a user a first-person virtual avatar can increase the accuracy of their egocentric distance judgments in an immersive virtual environment (IVE). This result provides one of the rare examples of a manipulation that can enable improved spatial task performance in a virtual environment without potentially compromising the ability for accurate information transfer to the real world. However, many open questions about the scope and limitations of the effectiveness of IVE avatar self-embodiment remain. In this paper, we report the results of a series of four experiments, involving a total of 40 participants, that explore the importance, to the desired outcome of enabling enhanced spatial perception accuracy, of providing a high level of geometric and motion fidelity in the avatar representation. In these studies, we assess participants' abilities to estimate egocentric distances in a novel virtual environment under four different conditions of avatar self-embodiment: a) no avatar; b) a fully tracked, custom-fitted, high fidelity avatar, represented using a textured triangle mesh; c) the same avatar as in b) but implemented with single point rather than full body tracking; and d) a fully tracked but simplified avatar, represented by a collection of small spheres at the raw tracking marker locations. The goal of these investigations is to attain insight into what specific characteristics of a virtual avatar representation are most important to facilitating accurate spatial perception, and what cost-saving measures in the avatar implementation might be possible. Our results indicate that each of the simplified avatar implementations we tested is significantly less effective than the full avatar in facilitating accurate distance estimation; in fact, the participants who were given the simplified avatar representations performed only marginally (but not significantly) more accurately than the participants who were given no avatar at all. These findings suggest that the beneficial impact of providing users with a high fidelity avatar self-representation may stem less directly from the low-level size and motion cues that the avatar embodiment makes available to them than from the cognitive sense of presence that the self-embodiment supports.

Previous research has shown that egocentric distance estimation suffers from compression in virtual environments when viewed through head mounted displays. Though many possible variables and factors have been investigated, the source of the compression is yet to be fully realized. Recent experiments have hinted in the direction of an unsatisfied feeling of presence being the cause. This paper investigates this presence hypothesis by exploring the benefit of providing self-embodiment to the user through the form of a virtual avatar, presenting an experiment comparing errors in egocentric distance perception through direct-blind walking between subjects with a virtual avatar and without. The result of this experiment finds a significant improvement with egocentric distance estimations for users equipped with a virtual avatar over those without.

Enabling veridical spatial perception in immersive virtual environments (IVEs) is an important yet elusive goal, as even the factors implicated in the often-reported phenomenon of apparent distance compression in HMD-based IVEs have yet to be satisfactorily elucidated. In recent experiments (Interrante et al., 2006), we have found that participants appear less prone to significantly underestimate egocentric distances in HMD-based IVEs, relative to in the real world, in the special case that they unambiguously know, through first-hand observation, that the presented virtual environment is a high fidelity 3D model of their concurrently occupied real environment. We had hypothesized that this increased veridicality might be due to participants having a stronger sensation of 'presence' in the IVE under these conditions of co-location, which state of mind leads them to act on their visual input in the IVE similarly as they would in the real world (the presence hypothesis). However, alternative hypotheses are also possible. Primary among these is the visual calibration hypothesis: participants could be relying on metric information gleaned from their exposure to the real environment to calibrate their judgments of sizes and distances in the matched virtual environment. It is important to disambiguate between the presence and visual calibration hypotheses because they suggest different directions for efforts to facilitate veridical distance perception in general (non-co-located) IVEs. In this paper, we present the results of an experiment that seeks novel insight into this question. Using a mixed within- and between-subjects design, we compare participants' relative ability to accurately estimate egocentric distances in three different virtual environment models: one that is an identical match to the occupied real environment; one in which each of the walls in our virtual room model has been surreptitiously moved ~10% inward towards the center of the room; and one in which each of the walls has been surreptitiously moved ~10% outwards from the center of the room. If the visual calibration hypothesis holds, then we should expect to see a degradation in the accuracy of peoples' distance judgments in the surreptitiously modified models, manifested as an underestimation of distances when the IVE is actually larger than the real room and as an overestimation of distances when the IVE is smaller. However, what we found is that distances were significantly underestimated in the virtual environment relative to in the real world in each of the surreptitiously modified room environments, while remaining reasonably accurate (consistent with our previous findings) in the case of the faithfully size-matched room environment. In a post-test survey, participants in each of the three room size conditions reported equivalent subjective levels of presence and did not indicate any overt awareness of the room size manipulation

In many applications, it is important to understand the individual values of, and relationships between, multiple related scalar variables defined across a common domain. Several approaches have been proposed for representing data in these situations. In this paper we focus on strategies for the visualization of multivariate data that rely on color mixing. In particular, through a series of controlled observer experiments, we seek to establish a fundamental understanding of the information-carrying capacities of two alternative methods for encoding multivariate information using color: color blending and color weaving. We begin with a baseline experiment in which we assess participants' abilities to accurately read numerical data encoded in six different basic color scales defined in the L*a*b* color space. We then assess participants' abilities to read combinations of 2, 3, 4 and 6 different data values represented in a common region of the domain, encoded using either color blending or color weaving. In color blending a single mixed color is formed via linear combination of the individual values in L*a*b* space, and in color weaving the original individual colors are displayed side-by-side in a high frequency texture that fills the region. A third experiment was conducted to clarify some of the trends regarding the color contrast and its effect on the magnitude of the error that was observed in the second experiment. The results indicate that when the component colors are represented side-by-side in a high frequency texture, most participants' abilities to infer the values of individual components are significantly improved, relative to when the colors are blended. Participants' performance was significantly better with color weaving particularly when more than 2 colors were used, and even when the individual colors subtended only 3 minutes of visual angle in the texture. However, the information-carrying capacity of the color weaving approach has its limits. We found that participants' abilities to accurately interpret each of the individual components in a high frequency color texture typically falls off as the number of components increases from 4 to 6. We found no significant advantages, in either color blending or color weaving, to using color scales based on component hues thatare more widely separated in the L*a*b* color space. Furthermore, we found some indications that extra difficulties may arise when opponent hues are employed.

Numerous previous studies have suggested that distances appear to be compressed in immersive virtual environments presented via head mounted display systems, relative to in the real world. However, the principal factors that are responsible for this phenomenon have remained largely unidentified. In this paper we shed some new light on this intriguing problem by reporting the results of two recent experiments in which we assess egocentric distance perception in a high fidelity, low latency, immersive virtual environment that represents an exact virtual replica of the participant’s concurrently occupied real environment. Under these novel conditions, we make the startling discovery that distance perception appears not to be significantly compressed in the immersive virtual environment, relative to in the real world.

No abstract available.

In this paper we offer new, texture-based methods for the visualization of multivariate data. These methods aim to more effectively convey the results of calculations simulating the formation of nanoparticles in turbulent fl ows. In these simulations, an entire distribution of nanoparticles is computed at every point across a two-dimensional slice of the data space, for every time step. Previous visualization methods have relied on multiple separate images to convey summary statistics about the datasets, including mean diameter and standard deviation of particle sizes. We introduce new methods based on texture which aim to enable the integrated understanding of the entire distribution of values at each point across the domain in terms of both summary statistics at each point and particle counts for various sizes of particles. Pointillism is used to represent the data at each point across the data range as a high-resolution texture. Circular glyphs can also be used to form a more discrete, spot-based texture, in which different characteristics of the distribution are encoded in various features of the spots.

In this paper we offer methods for visualization of the formation of nanoparticles in turbulent flows. We present the use of pointillism as a technique to convey the distribution of nanoparticle sizes as texture in an area. We also demonstrate a method of producing and packing spot glyphs representative of the distribution of nanoparticle sizes at every point in the flow to produce an intuitive and extensible framework for the visualization.

The visualization of any vector field is dependent on the relative velocity of the observer. In experimentally generated vector fields, the average value of the streamwise component of the global vector field is typically calculated and subtracted from each vector. We demonstrate that the resulting image, critical points, and vector field features are greatly influenced by the magnitude of the value subtracted from the streamwise velocity.

There are a number of applications in computer graphics that require as a first step the accurate estimation of principal direction vectors at arbitrary vertices on a triangulated surface. Although several methods for calculating principal directions over such models have been previously proposed, we have found in practice that all exhibit unexplained large errors in some cases. In this article, we describe our theoretical and experimental investigations into possible sources of errors in the approximation of principal direction vectors from triangular meshes, and suggest a new method for estimating principal directions that can yield better results under some circumstances.

In this paper, we describe the results of two comprehensive controlled observer experiments intended to yield insight into the following question: If we could design the ideal texture pattern to apply to an arbitrary smoothly curving surface in order to enable its 3D shape to be most accurately and effectively perceived, what would the characteristics of that texture pattern be? We begin by reviewing the results of our initial study in this series, which were presented at the 2003 IEEE Symposium on Information Visualization, and offer an expanded analysis of those findings. We continue by presenting the results of a follow-on study in which we sought to more specifically investigate the separate and combined influences on shape perception of particular texture components, with the goal of obtaining a clearer view of their potential information carrying capacities. In each study, we investigated the observers' ability to identify the intrinsic shape category of a surface patch (elliptical, hyperbolic, cylindrical, or flat) and its extrinsic surface orientation (convex, concave, both, or neither). In our first study, we compared performance under eight different texture type conditions, plus two projection conditions (perspective or orthographic) and two viewing conditions (head-on or oblique). In this study, we found that: 1) Shape perception was better facilitated, in general, by the bidirectional "principal direction grid" pattern than by any of the seven other patterns tested; 2) shape type classification accuracy remained high under the orthographic projection condition for some texture types when the viewpoint was oblique; 3) perspective projection was required for accurate surface orientation classification; and 4) shape classification accuracy was higher when the surface patches were oriented at a (generic) oblique angle to the line of sight than when they were oriented (in a nongeneric pose) to face the viewpoint straight on. In our second study, we compared performance under eight new texture type conditions, redesigned to facilitate gathering insight into the cumulative effects of specific individual directional components in a wider variety of multidirectional texture patterns. In this follow-on study, we found that shape classification accuracy was equivalently good under a variety of test patterns that included components following either the first or first and second principal directions, in addition to other directions, suggesting that a principal direction grid texture is not the only possible "best option" for enhancing shape representation.

In this paper we offer several new insights and techniques for effectively using color and texture to simultaneously convey information about multiple 2D scalar and vector distributions, in a way that facilitates allowing each distribution to be understood both individually and in the context of one or more of the other distributions. Specifically, we introduce the concepts of: color weaving for simultaneously representing information about multiple co-located color encoded distributions; and texture stitching for achieving more spatially accurate multi-frequency line integral convolution representations of combined scalar and vector distributions. The target application for our research is the definition, detection and visualization of regions of interest in a turbulent boundary layer flow at moderate Reynolds number. In this work, we examine and analyze streamwise-spanwise planes of three-component velocity vectors with the goal of identifying and characterizing spatially organized packets of hairpin vortices.

Considerable evidence suggests that a viewer's perception of the 3D shape of a polygonally-defined object can be significantly affected (either masked or enhanced) by the presence of a surface texture pattern. However, investigations into the specific mechanisms of texture's effect on shape perception are still ongoing and the question of how to design and apply a texture pattern to a surface in order to best facilitate shape perception remains open. Recently, we have suggested that, for anisotropic texture patterns, the accuracy of shape judgments may be significantly affected by the orientation of the surface texture pattern anisotropy with respect to the principal directions of curvature over the surface. However, it has been difficult, until this time, to conduct controlled studies specifically investigating the effect of texture orientation on shape perception because there has been no simple and reliable method for texturing an arbitrary doubly curved surface with a specified input pattern such that the dominant orientation of the pattern everywhere follows a predefined directional vector field over the surface, while seams and projective distortion of the pattern are avoided. In this paper, we present a straightforward and highly efficient method for achieving such a texture and describe how it can potentially be used to enhance shape representation. Specifically, we describe a novel, efficient, automatic algorithm for seamlessly synthesizing, from a sample 2D pattern, a high resolution fitted surface texture in which the dominant orientation of the pattern locally follows a specified vector field over the surface at a per-pixel level and in which seams, projective distortion, and repetition artifacts in the texture pattern are nearly completely avoided. We demonstrate the robustness of our method with a variety of texture swatches applied to standard graphics data sets and we explain how our method can be used to facilitate research in the perception of shape from texture.

This paper describes how the set of principal directions and principal curvatures can be understood to define a natural "flow" over the surface of an object and, as such, can be used to guide the placement of the lines of a stroke texture that seeks to represent 3D shape in a perceptually intuitive way.The driving application for this work is the visualization of layered isovalue surfaces in volume data, where the particular identity of an individual surface is not generally known a priori and observers will typically wish to view a variety of different level surfaces from the same distribution, superimposed over underlying opaque structures.This paper describes how, by advecting an evenly distributed set of tiny opaque particles, and the empty space between them, via 3D line integral convolution through the vector field defined by the principal directions and principal curvatures of the level surfaces passing through each gridpoint of a 3D volume, it is possible to generate a single scan-converted solid stroke texture that can be used to illustrate the essential shape information of any level surface in the data.By redefining the length of the filter kernel according to the magnitude of the maximum principal curvature of the level surface at each point around which the convolution is applied, one can generate longer strokes over more the highly curved areas, where the directional information is both most stable and most relevant, and at the same time downplay the visual impact of the directional information indicated by the stroke texture in the flatter regions.In a voxel-based approach such as this one, stroke narrowness will be constrained by the resolution of the volume within which the texture is represented.However, by adaptively indexing into multiple pre-computed texture volumes, obtained by advecting particles of increasing sizes, one may selectively widen the strokes at any point by a variable amount, determined at the time of rendering, to reflect shading information or any other function defined over the volume data.

This paper discusses strategies for effectively portraying 3D flow using volume line integral convolution. Issues include defining an appropriate input texture, clarifying the distinct identities and relative depths of the advected texture elements, and selectively highlighting regions of interest in both the input and output volumes. Apart from offering insights into the greater potential of 3D LIC as a method for effectively representing flow in a volume, a principal contribution of this work is the suggestion of a technique for generating and rendering 3D visibility-impeding "halos" that can help to intuitively indicate the presence of depth discontinuities between contiguous elements in a projection and thereby clarify the 3D spatial organization of elements in the flow. The proposed techniques are applied to the visualization of a hot, supersonic, laminar jet exiting into a colder, subsonic coflow.

The paper discusses techniques for extracting feature lines from three-dimensional unstructured grids. The twin objectives are to facilitate the interactive manipulation of these typically very large and dense meshes, and to clarify the visualization of the solution data that accompanies them. The authors describe the perceptual importance of specific viewpoint-dependent and view-independent features, discuss the relative advantages and disadvantages of several alternative algorithms for identifying these features (taking into consideration both local and global criteria), and demonstrate the results of these methods on a variety of different data sets.

Transparency can be a useful device for depicting multiple overlapping surfaces in a single image. The challenge is to render the transparent surfaces in such a way that their 3D shape can be readily understood and their depth distance from underlying structures clearly perceived. This paper describes our investigations into the use of sparsely-distributed discrete, opaque texture as an artistic device for more explicitly indicating the relative depth of a transparent surface and for communicating the essential features of its 3D shape in an intuitively meaningful and minimally occluding way. The driving application for this work is the visualization of layered surfaces in radiation therapy treatment planning data, and the technique is illustrated on transparent isointensity surfaces of radiation dose. We describe the perceptual motivation and artistic inspiration for defining a stroke texture that is locally oriented in the direction of greatest normal curvature (and in which individual strokes are of a length proportional to the magnitude of the curvature in the direction they indicate), and we discuss two alternative methods for applying this texture to isointensity surfaces defined in a volume. We propose an experimental paradigm for objectively measuring observers' ability to judge the shape and depth of a layered transparent surface, in the course of a task which is relevant to the needs of radiotherapy treatment planning, and use this paradigm to evaluate the practical effectiveness of our approach through a controlled observer experiment based on images generated from actual clinical data.

Transparency can be a useful device for simultaneously depicting multiple superimposed layers of information in a single image. However, in computer-generated pictures-as in photographs and in directly viewed actual objects-it can often be difficult to adequately perceive the three-dimensional shape of a layered transparent surface or its relative depth distance from underlying structures. Inspired by artists' use of line to show shape, we have explored methods for automatically defining a distributed set of opaque surface markings that intend to portray the three-dimensional shape and relative depth of a smoothly curving layered transparent surface in an intuitively meaningful (and minimally occluding) way. This paper describes the perceptual motivation, artistic inspiration and practical implementation of an algorithm for "texturing" a transparent surface with uniformly distributed opaque short strokes, locally oriented in the direction of greatest normal curvature, and of length proportional to the magnitude of the surface curvature in the stroke direction. The driving application for this work is the visualization of layered surfaces in radiation therapy treatment planning data, and the technique is illustrated on transparent isointensity surfaces of radiation dose.

There are many applications that can benefit from the simultaneous display of multiple layers of data. The objective in these cases is to render the layered surfaces in a such way that the outer structures can be seen and seen through at the same time. The paper focuses on the particular application of radiation therapy treatment planning, in which physicians need to understand the three dimensional distribution of radiation dose in the context of patient anatomy. We describe a promising technique for communicating the shape and position of the transparent skin surface while at the same time minimally occluding underlying isointensity dose surfaces and anatomical objects: adding a sparse, opaque texture comprised of a small set of carefully chosen lines. We explain the perceptual motivation for explicitly drawing ridge and valley curves on a transparent surface, describe straightforward mathematical techniques for detecting and rendering these lines, and propose a small number of reasonably effective methods for selectively emphasizing the most perceptually relevant lines in the display.