Personal computers and handheld devices provide keyboard shortcuts and swipe gestures to enable users to efficiently switch between applications, whereas today’s virtual reality (VR) systems do not. In this work, we present an exploratory study on user interface aspects to support efficient switching between worlds in VR. We created eight interfaces that afford previewing and selecting from the available virtual worlds, including methods using portals and worlds-in-miniature (WiMs). To evaluate these methods, we conducted a controlled within-subjects empirical experiment (N=22) where participants frequently transitioned between six different environments to complete an object collection task. Our quantitative and qualitative results show that WiMs supported rapid acquisition of high-level spatial information while searching and were deemed most efficient by participants while portals provided fast pre-orientation. Finally, we present insights into the applicability, usability, and effectiveness of the VR world switching methods we explored, and provide recommendations for their application and future context/world switching techniques and interfaces.

Advances in artificial intelligence and embodied interaction in augmented reality (AR) are creating new opportunities for intelligent instructional systems that dynamically adapt to individual learners. However, sustaining real-time responsiveness while preserving natural, socially meaningful interaction remains a persistent challenge. This work introduces ARIA (Augmented Reality Instructional Agent), a real-time software architecture for embodied AI instruction in augmented reality. ARIA leverages large language models (LLMs) with adaptive prompt engineering to tailor dialogue style, instructional strategy, and persona expression to each user. Its modular pipeline is optimized for robust, low-latency performance, with benchmarks reported for responsiveness and system stability. To complement the technical evaluation, user experience was assessed through standardized questionnaires, offering insights into perceived personalization, trust, and interaction quality. Quantitative and qualitative results demonstrate that ARIA achieves sub-second responsiveness, high pragmatic and hedonic usability, and a strong sense of co-presence and instructional trust. This work contributes a unified framework and reference architecture for developing adaptive embodied agents that combine technical efficiency with human-centered design, highlighting how real-time responsiveness can serve as the foundation for relational engagement in embodied AI instruction.

While embodied conversational agents driven by Large Language Models (LLMs) are emerging as valuable tools for instruction in Augmented Reality (AR), a key challenge lies in crafting their personalities to optimize both instructional efficacy and user engagement. To address this, we present findings from a within-subjects experiment that compared task performance and user experience with a LEGO assembly task. Participants received guidance from a real human instructor and three virtual counterparts, whose Big Five personality profiles were designed to be: (1) a direct replica of the real human, (2) an "ideal" profile ba sed on pedagogical research, or (3) customized by the participant. Our results reveal a critical trade-off: instruction from the real expert resulted in superior task efficiency and clarity; however, among the virtual conditions, instructors with idealized or user-customized personalities fostered significantly higher levels of user engagement and social presence compared to the virtual replica. Crucially, allowing users to customize their instructor's persona led to the strongest preference for future interaction. These findings underscore that personality is a fundamental component in the design of AI-driven instructors, providing empirical evidence for navigating the balance between task-oriented guidance and personalized, socially resonant user experiences.

Teleportation has become a popular locomotion method for virtual reality due to lesser demands on physical space and decreased levels of motion sickness compared to other methods. However, prior work has shown that these advantages come at the cost of impaired spatial perception and awareness, the extent to which is still largely unknown. In this work, we present a within-subjects study (N = 29) that explores the effects of teleportation on spatial perception by investigating how much humans can be unknowingly displaced relative to their intended destination during teleportation. After teleporting to the specified location, participants indicated the direction and magnitude (small, medium, large) of the perceived shift or rotation. Displacement from the target happened either as a translation in the forward- or strafe-axis, or a rotation about the up-axis at the intended target. Each displacement condition included eleven offsets that were repeated six times. Our results indicate points of subjective equality, which show a significant perceptual shift along the forward-direction, as well as detection thresholds, which indicate a comparatively wide range in which humans are unable to detect induced shifts. Furthermore, our results show that even if humans are able to detect these shifts, larger ones can be introduced before their magnitudes are rated as medium or large, which provides ample opportunities for interface designers who want to leverage these results in virtual reality.

The swift advancement of drone technology presents new challenges in data analysis and integration as deployments increase. This paper addresses the complexities of managing multiple drone video feeds and controlling autonomous drone swarms to enhance situational awareness through the use of real-time updated digital twins for drone swarm command and control. We aim to enhance the effectiveness of drone swarm operations by introducing a novel method, Camera-based Adaptive Line Formation and Dynamic Leader-following Optimization (CALF-DLFO). We investigate the impact of this novel control method on area coverage and drone distribution, considering factors such as formation direction, speed, separation distance, and adjustments. Simulation experiments demonstrate a significant improvement in area coverage compared to prior methods which focused on isolated segments. Our camera-based adaptive line formation, combined with efficient drone control mechanisms, not only enhances coverage but also provides a promising approach to scalable and automated drone swarm management.

In most cases, retaining memories of things we have experienced in the past is desirable, but in some cases, we want to clear our minds so that we may focus completely on subsequent activities. When someone switches from one task to another, they commonly incur some “cognitive residue” where some of their cognitive resources such as working memory and attention remain devoted to their previous task even after they try to switch their focus to their new task. This residue could have a negative impact on their performance in the next task, and in such circumstances, it is important to reduce that residue. In this paper, we explore the concept of cognitive residue in the context of switching between virtual reality (VR) environments. We conducted a human-subject experiment (N=24) with a spatial recall task to investigate how different visual transitions might reduce participants’ spatial cognitive residue. In this instance, more errors on the recall task corresponds to less spatial cognitive residue. We found that transitions that lasted one minute successfully reduced spatial cognitive residue: they significantly reduced participants’ abilities to recall the positions of objects in their previous VE compared to an instantaneous cut transition. Additionally, for transitions that showed a nature scene, greater head movement significantly correlated with more spatial memory errors (i.e., less spatial cognitive residue). We discuss how these findings can be applied to support users transitioning between virtual tasks and environments in VR task switching scenarios.

Augmented reality (AR) head-mounted displays (HMDs) provide users with a view in which digital content is blended spatially with the outside world. However, one critical issue faced with such display technologies is misperception, i.e., perceptions of computer-generated content that differs from our human perception of other real-world objects or entities. Misperception can lead to mistrust in these systems and negative impacts in a variety of application fields. Although there is a considerable amount of research investigating either size, distance, or speed misperception in AR, far less is known about the relationships between these aspects. In this paper, we present an outdoor AR experiment (N = 20) using a HoloLens 2 HMD. Participants estimated size, distance, and speed of Familiar and Unfamiliar outdoor animals at three distances (30, 60, 90 meters). To investigate whether providing information about one aspect may influence another, we divided our experiment into three phases. In Phase I, participants estimated the three aspects without any provided information. In Phase II, participants were given accurate size information, then asked to estimate distance and speed. In Phase III, participants were given accurate distance and size information, then asked to estimate speed. Our results show that estimates of speed in particular of the Unfamiliar animals benefited from provided size information, while speed estimates of all animals benefited from provided distance information. We found no support for the assumption that distance estimates benefited from provided size information.

Redirected walking is a locomotion technique that allows users to naturally walk through large immersive virtual environments (IVEs) by guiding them on paths that might vary from the paths they walk in the real world. While this technique enables the exploration of larger spaces in the IVE via natural walking, previous work has shown that it induces extra cognitive load for the users. On the other hand, previous research has shown that exposure to virtual nature environments can restore users’ diminished attentional capacities and lead to enhanced cognitive performances. Therefore, the aim of this paper is to investigate if the environment in which the user is redirected has the potential to reduce its cognitive demands. For this purpose, we conducted an experiment with 28 participants, who performed a spatial working memory task (i.e., 2-back test) while walking and being redirected with different gains in two different IVEs (i.e., (i) forest and (ii) urban). The results of frequentist and Bayesian analysis are consistent and provide evidence against an effect of the type of IVE on detection thresholds as well as cognitive and locomotion performances. Therefore, redirected walking is robust to the variation of the IVEs tested in this experiment. The results partly challenge previous research findings and, therefore, require future work in this direction.

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.

It is not uncommon for science fiction movies to portray futuristic user interfaces that can only be realized decades later with state-of-the-art technology. In this work, we present a prototypical augmented reality (AR) installation that was inspired by the movie The Time Machine (2002). It consists of a transparent screen that acts as a window through which users can see the stereoscopic projection of a three-dimensional virtual human (VH). However, there are some key differences between the vision of this technology and the way VHs on these displays are actually perceived. In particular, the additive light model of these displays causes darker VHs to appear more transparent, while light in the physical environment further increases transparency, which may affect the way VHs are perceived, to what degree they are trusted, and the distances one maintains from them in a spatial setting. In this paper, we present a user study in which we investigate how transparency in the scope of transparent AR screens affects the perception of a VH’s appearance, social presence with the VH, and the social space around users as defined by proxemics theory. Our results indicate that appearances are comparatively robust to transparency, while social presence improves in darker physical environments, and proxemic distances to the VH largely depend on one’s distance from the screen but are not noticeably affected by transparency. Overall, our results suggest that such transparent AR screens can be an effective technology for facilitating social interactions between users and VHs in a shared physical space.

The expression of human emotion is integral to social interaction, and in virtual reality it is increasingly common to develop virtual avatars that attempt to convey emotions by mimicking these visual and aural cues, i.e. the facial and vocal expressions. However, errors in (or the absence of) facial tracking can result in the rendering of incorrect facial expressions on these virtual avatars. For example, a virtual avatar may speak with a happy or unhappy vocal inflection while their facial expression remains otherwise neutral. In circumstances where there is conflict between the avatar's facial and vocal expressions, it is possible that users will incorrectly interpret the avatar's emotion, which may have unintended consequences in terms of social influence or in terms of the outcome of the interaction. In this paper, we present a human-subjects study (N = 22) aimed at understanding the impact of conflicting facial and vocal emotional expressions. Specifically we explored three levels of emotional valence (unhappy, neutral, and happy) expressed in both visual (facial) and aural (vocal) forms. We also investigate three levels of head scales (down-scaled, accurate, and up-scaled) to evaluate whether head scale affects user interpretation of the conveyed emotion. We find significant effects of different multimodal expressions on happiness and trust perception, while no significant effect was observed for head scales. Evidence from our results suggest that facial expressions have a stronger impact than vocal expressions. Additionally, as the difference between the two expressions increase, the less predictable the multimodal expression becomes. For example, for the happy-looking and happy-sounding multimodal expression, we expect and see high happiness rating and high trust, however if one of the two expressions change, this mismatch makes the expression less predictable. We discuss the relationships, implications, and guidelines for social applications that aim to leverage multimodal social cues.

Speech perception is optimal in quiet environments, but noise can impair comprehension and increase errors. In these situations, lip reading can help, but it is not always possible, such as during an audio call or when wearing a face mask. One approach to improve speech perception in these situations is to use an artificial visual lip reading aid. In this paper, we present a user study (N = 17) in which we compared three levels of audio stimuli visualizations and two levels of modulating the appearance of the visualization based on the speech signal, and we compared them against two control conditions: an audio-only condition, and a real human speaking. We measured participants’ speech reception thresholds (SRTs) to understand the effects of these visualizations on speech perception in noise. These thresholds indicate the decibel levels of the speech signal that are necessary for a listener to receive the speech correctly 50% of the time. Additionally, we measured the usability of the approaches and the user experience. We found that the different artificial visualizations improved participants’ speech reception compared to the audio-only baseline condition, but they were significantly poorer than the real human condition. This suggests that different visualizations can improve speech perception when the speaker’s face is not available. However, we also discuss limitations of current plug-and-play lip sync software and abstract representations of the speaker in the context of speech perception.

Various reasons exist why humans desire to magnify portions of our visually perceived surroundings, e.g., because they are too far away or too small to see with the naked eye. Different technologies are used to facilitate magnification, from telescopes to microscopes using monocular or binocular designs. In particular, modern digital cameras capable of optical and/or digital zoom are very flexible as their high-resolution imagery can be presented to users in real-time with displays and interfaces allowing control over the magnification. In this paper, we present a novel design space of intuitive augmented reality (AR) magnifications where an AR head-mounted display is used for the presentation of real-time magnified camera imagery. We present a user study evaluating and comparing different visual presentation methods and AR interaction techniques. Our results show different advantages for unimanual, bimanual, and situated AR magnification window interfaces, near versus far vergence distances for the image presentation, and five different user interfaces for specifying the scaling factor of the imagery.

Extended reality (XR) technologies, such as virtual reality (VR) and augmented reality (AR), provide users, their avatars, and embodied agents a shared platform to collaborate in a spatial context. Although traditional face-to-face communication is limited by users’ proximity, meaning that another human’s non-verbal embodied cues become more difficult to perceive the farther one is away from that person, researchers and practitioners have started to look into ways to accentuate or amplify such embodied cues and signals to counteract the effects of distance with XR technologies. In this article, we describe and evaluate the Big Head technique, in which a human’s head in VR/AR is scaled up relative to their distance from the observer as a mechanism for enhancing the visibility of non-verbal facial cues, such as facial expressions or eye gaze. To better understand and explore this technique, we present two complimentary human-subject experiments in this article. In our first experiment, we conducted a VR study with a head-mounted display to understand the impact of increased or decreased head scales on participants’ ability to perceive facial expressions as well as their sense of comfort and feeling of “uncannniness” over distances of up to 10 m. We explored two different scaling methods and compared perceptual thresholds and user preferences. Our second experiment was performed in an outdoor AR environment with an optical see-through head-mounted display. Participants were asked to estimate facial expressions and eye gaze, and identify a virtual human over large distances of 30, 60, and 90 m. In both experiments, our results show significant differences in minimum, maximum, and ideal head scales for different distances and tasks related to perceiving faces, facial expressions, and eye gaze, and we also found that participants were more comfortable with slightly bigger heads at larger distances. We discuss our findings with respect to the technologies used, and we discuss implications and guidelines for practical applications that aim to leverage XR-enhanced facial cues.

Human speech perception is generally optimal in quiet environments, however it becomes more difficult and error prone in the presence of noise, such as other humans speaking nearby or ambient noise. In such situations, human speech perception is improved by speech reading, i.e., watching the movements of a speaker's mouth and face, either consciously as done by people with hearing loss or subconsciously by other humans. While previous work focused largely on speech perception of two-dimensional videos of faces, there is a gap in the research field focusing on facial features as seen in head-mounted displays, including the impacts of display resolution, and the effectiveness of visually enhancing a virtual human face on speech perception in the presence of noise. In this paper, we present a comparative user study ( N=21) in which we investigated an audio-only condition compared to two levels of head-mounted display resolution ( 1832×1920 or 916×960 pixels per eye) and two levels of the native or visually enhanced appearance of a virtual human, the latter consisting of an up-scaled facial representation and simulated lipstick (lip coloring) added to increase contrast. To understand effects on speech perception in noise, we measured participants' speech reception thresholds (SRTs) for each audio-visual stimulus condition. These thresholds indicate the decibel levels of the speech signal that are necessary for a listener to receive the speech correctly 50% of the time. First, we show that the display resolution significantly affected participants' ability to perceive the speech signal in noise, which has practical implications for the field, especially in social virtual environments. Second, we show that our visual enhancement method was able to compensate for limited display resolution and was generally preferred by participants. Specifically, our participants indicated that they benefited from the head scaling more than the added facial contrast from the simulated lipstick. We discuss relationships, implications, and guidelines for applications that aim to leverage such enhancements.

In a future of pervasive augmented reality (AR), AR systems will need to be able to efficiently draw or guide the attention of the user to visual points of interest in their physical-virtual environment. Since AR imagery is overlaid on top of the user's view of their physical environment, these attention guidance techniques must not only compete with other virtual imagery, but also with distracting or attention-grabbing features in the user's physical environment. Because of the wide range of physical-virtual environments that pervasive AR users will find themselves in, it is difficult to design visual cues that "pop out" to the user without performing a visual analysis of the user's environment, and changing the appearance of the cue to stand out from its surroundings. In this article, we present an initial investigation into the potential uses of dichoptic visual cues for optical see-through AR displays, specifically cues that involve having a difference in hue, saturation, or value between the user's eyes. These types of cues have been shown to be preattentively processed by the user when presented on other stereoscopic displays, and may also be an effective method of drawing user attention on optical see-through AR displays. We present two user studies: one that evaluates the saliency of dichoptic visual cues on optical see-through displays, and one that evaluates their subjective qualities. Our results suggest that hue-based dichoptic cues or "Forbidden Colors" may be particularly effective for these purposes, achieving significantly lower error rates in a pop out task compared to value-based and saturation-based cues.

Social priming is the idea that observations of a virtual human (VH) engaged in short social interactions with a real or virtual human bystander can positively influence users’ subsequent interactions with that VH. In this paper we investigate the question of whether the positive effects of social priming are limited to interactions with humanoid entities. For instance, virtual dogs offer an attractive candidate for non-humanoid entities, as previous research suggests multiple positive effects. In particular, real human dog owners receive more positive attention from strangers than non-dog owners.To examine the influence of such social priming we carried out a human-subjects experiment with four conditions: three social priming conditions where a participant initially observed a VH interacting with one of three virtual entities (another VH, a virtual pet dog, or a virtual personal robot), and a non-social priming condition where a VH (alone) was intently looking at her phone as if reading something. We recruited 24 participants and conducted a mixed-methods analysis. We found that a VH’s prior social interactions with another VH and a virtual dog significantly increased participants’ perceptions of the VHs’ affective attraction. Also, participants felt more inclined to interact with the VH in the future in all of the social priming conditions. Qualitatively, we found that the social priming conditions resulted in a more positive user experience than the non-social priming condition. Also, the virtual dog and the virtual robot were perceived as a source of positive surprise, with participants appreciating the non-humanoid interactions for various reasons, such as the avoidance of social anxieties sometimes associated with humans.

When medical caregivers transfer patients to another person’s care (a patient handoff), it is essential they effectively communicate the patient’s condition to ensure the best possible health outcomes. Emergency situations caused by mass casualty events (e.g., natural disasters) introduce additional difficulties to handoff procedures such as environmental noise. We created a projected mixed reality simulation of a handoff scenario involving a medical evacuation by air and tested how low, medium, and high levels of helicopter noise affected participants’ handoff experience, handoff performance, and behaviors. Through a human-subjects experimental design study (N = 21), we found that the addition of noise increased participants’ subjective stress and task load, decreased their self-assessed and actual performance, and caused participants to speak louder. Participants also stood closer to the virtual human sending the handoff information when listening to the handoff than they stood to the receiver when relaying the handoff information. We discuss implications for the design of handoff training simulations and avenues for future handoff communication research.

Current optical see-through displays in the field of augmented reality are limited in their ability to display colors with low lightness in the hue, saturation, lightness (HSL) color space, causing such colors to appear transparent. This hardware limitation may add unintended bias into scenarios with virtual humans. Humans have varying skin tones including HSL colors with low lightness. When virtual humans are displayed with optical see-through devices, people with low lightness skin tones may be displayed semi-transparently while those with high lightness skin tones will be displayed more opaquely. For example, a Black avatar may appear semi-transparent in the same scene as a White avatar who will appear more opaque. We present an exploratory user study ( N=160) investigating whether differing opacity levels result in dehumanizing avatar and human faces. Results support that dehumanization occurs as opacity decreases. This suggests that in similar lighting, low lightness skin tones (e.g., Black faces) will be viewed as less human than high lightness skin tones (e.g., White faces). Additionally, the perceived emotionality of virtual human faces also predicts perceived humanness. Angry faces were seen overall as less human, and at lower opacity levels happy faces were seen as more human. Our results suggest that additional research is needed to understand the effects and interactions of emotionality and opacity on dehumanization. Further, we provide evidence that unintentional racial bias may be added when developing for optical see-through devices using virtual humans. We highlight the potential bias and discuss implications and directions for future research.

The closed design of virtual reality (VR) head-mounted displays substantially limits users’ awareness of their real-world surroundings. This presents challenges when another person in the same physical space needs to interrupt the VR user for a brief conversation. Such interruptions, e.g., tapping a VR user on the shoulder, can cause a disruptive break in presence (BIP), which affects their place and plausibility illusions, and may cause a drop in performance of their virtual activity. Recent findings related to the concept of diegesis, which denotes the internal consistency of an experience/story, suggest potential benefits of integrating registered virtual representations for physical interactors, especially when these appear internally consistent in VR. In this paper, we present a human-subject study we conducted to compare and evaluate five different diegetic and non-diegetic methods to facilitate cross-reality interruptions in a virtual office environment, where a user’s task was briefly interrupted by a physical person. We created a Cross-Reality Interaction Questionnaire (CRIQ) to capture the quality of the interaction from the VR user’s perspective. Our results show that the diegetic representations afforded reasonably high senses of co-presence, the highest quality interactions, the highest place illusions, and caused the least disruption of the participants’ virtual experiences. We discuss our findings as well as implications for practical applications that aim to leverage virtual representations to ease cross-reality interruptions.

Previous research on distance estimation in virtual reality (VR) has well established that even for geometrically accurate virtual objects and environments users tend to systematically mis-estimate distances. This has implications for Social VR, where it introduces variables in personal space and proxemics behavior that change social behaviors compared to the real world. One yet unexplored factor is related to the trend that avatars' embodied cues in Social VR are often scaled, e.g., by making one's head bigger or one's voice louder, to make social cues more pronounced over longer distances. In this paper we investigate how the perception of avatar distance is changed based on two means for scaling embodied social cues: visual head scale and verbal volume scale. We conducted a human-subject study employing a mixed factorial design with two Social VR avatar representations (full-body, head-only) as a between factor as well as three visual head scales and three verbal volume scales (up-scaled, accurate, down-scaled) as within factors. For three distances from social to far-public space, we found that visual head scale had a significant effect on distance judgments and should be tuned for Social VR, while conflicting verbal volume scales did not, indicating that voices can be scaled in Social VR without immediate repercussions on spatial estimates. We discuss the interactions between the factors and implications for Social VR.

Light-on-dark color schemes, so-called “Dark Mode,” are becoming more and more popular over a wide range of display technologies and application fields. Many people who have to look at computer screens for hours at a time, such as computer programmers and computer graphics artists, indicate a preference for switching colors on a computer screen from dark text on a light background to light text on a dark background due to perceived advantages related to visual comfort and acuity, specifically when working in low-light environments. In this article, we investigate the effects of dark mode color schemes in the field of optical see-through head-mounted displays (OST-HMDs), where the characteristic “additive” light model implies that bright graphics are visible but dark graphics are transparent . We describe two human-subject studies in which we evaluated a normal and inverted color mode in front of different physical backgrounds and different lighting conditions. Our results indicate that dark mode graphics displayed on the HoloLens have significant benefits for visual acuity and usability, while user preferences depend largely on the lighting in the physical environment. We discuss the implications of these effects on user interfaces and applications.

Virtual steering techniques enable users to navigate in larger Virtual Environments (VEs) than the physical workspace available. Even though these techniques do not require physical movement of the users (e.g. using a joystick and the head orientation to steer towards a virtual direction), recent work observed that users might unintentionally move in the physical workspace while navigating, resulting in Unintended Positional Drift (UPD). This phenomenon can be a safety issue since users may unintentionally reach the physical boundaries of the workspace while using a steering technique. In this context, as a necessary first step to improve the design of navigation techniques minimizing the UPD, this paper aims at analyzing and modeling the UPD during a virtual navigation task. In particular, we characterize and analyze the UPD for a dataset containing the positions and orientations of eighteen users performing a virtual slalom task using virtual steering techniques. Participants wore a head-mounted display and had to follow three different sinusoidal-like trajectories (with low, medium and high curvature) using a torso-steering navigation technique. We analyzed the performed motions and proposed two UPD models: the first based on a linear regression analysis and the second based on a Gaussian Mixture Model (GMM) analysis. Then, we assessed both models through a simulation-based evaluation where we reproduced the same navigation task using virtual agents. Our results indicate the feasibility of using simulation-based evaluations to study UPD. The paper concludes with a discussion of potential applications of the results in order to gain a better understanding of UPD during steering and therefore improve the design of navigation techniques by compensating for UPD.

In this article, we investigate the effects of the physical influence of a virtual human (VH) in the context of face-to-face interaction in a mixed reality environment. In Experiment 1, participants played a tabletop game with a VH, in which each player takes a turn and moves their own token along the designated spots on the shared table. We compared two conditions as follows: the VH in the virtual condition moves a virtual token that can only be seen through augmented reality (AR) glasses, while the VH in the physical condition moves a physical token as the participants do; therefore the VH's token can be seen even in the periphery of the AR glasses. For the physical condition, we designed an actuator system underneath the table. The actuator moves a magnet under the table which then moves the VH's physical token over the surface of the table. Our results indicate that participants felt higher co-presence with the VH in the physical condition, and participants assessed the VH as a more physical entity compared to the VH in the virtual condition. We further observed transference effects when participants attributed the VH's ability to move physical objects to other elements in the real world. Also, the VH's physical influence improved participants' overall experience with the VH. In Experiment 2, we further looked into the question how the physical-virtual latency in movements affected the perceived plausibility of the VH's interaction with the real world. Our results indicate that a slight temporal difference between the physical token reacting to the virtual hand's movement increased the perceived realism and causality of the mixed reality interaction. We discuss potential explanations for the findings and implications for future shared mixed reality tabletop setups.

360-degree experiences such as cinematic virtual reality and 360-degree videos are becoming increasingly popular. In most examples, viewers can freely explore the content by changing their orientation. However, in some cases, this increased freedom may lead to viewers missing important events within such experiences. Thus, a recent research thrust has focused on studying mechanisms for guiding viewers' attention while maintaining their sense of presence and fostering a positive user experience. One approach is the utilization of diegetic mechanisms, characterized by an internal consistency with respect to the narrative and the environment, for attention guidance. While such mechanisms are highly attractive, their uses and potential implementations are still not well understood. Additionally, acknowledging the user in 360-degree experiences has been linked to a higher sense of presence and connection. However, less is known when acknowledging behaviors are carried out by attention guiding mechanisms. To close these gaps, we conducted a within-subjects user study with five conditions of no guide and virtual arrows, birds, dogs, and dogs that acknowledge the user and the environment. Through our mixed-methods analysis, we found that the diegetic virtual animals resulted in a more positive user experience, all of which were at least as effective as the non-diegetic arrow in guiding users towards target events. The acknowledging dog received the most positive responses from our participants in terms of preference and user experience and significantly improved their sense of presence compared to the non-diegetic arrow. Lastly, three themes emerged from a qualitative analysis of our participants' feedback, indicating the importance of the guide's blending in, its acknowledging behavior, and participants' positive associations as the main factors for our participants' preferences.

Virtual reality (VR) technologies provide a shared platform for collaboration among users in a spatial context. To enhance the quality of social signals during interaction between users, researchers and practitioners started augmenting users’ interpersonal space with different types of virtual embodied social cues. A prominent example is commonly referred to as the "Big Head" technique, in which the head scales of virtual interlocutors are slightly increased to leverage more of the display’s visual space to convey facial social cues. While beneficial in improving interpersonal social communication, the benefits and thresholds of human perception of facial cues and comfort in such Big Head environments are not well understood, limiting their usefulness and subjective experience.In this paper, we present a human-subject study that we conducted to understand the impact of an increased or decreased head scale in social VR on participants’ ability to perceive facial expressions as well as their sense of comfort and feeling of "uncanniness." We explored two head scaling methods and compared them with respect to perceptual thresholds and user preferences. We further show that the distance to interlocutors has an important effect on the results. We discuss implications and guidelines for practical applications that aim to leverage VR-enhanced social cues.

Past work in augmented reality has shown that temperature-associated AR stimuli can induce warming and cooling sensations in the user, and prior work in psychology suggests that a person’s body temperature can influence that person’s sense of subjective perception of duration. In this paper, we present a user study to evaluate the relationship between temperature-associated virtual stimuli presented on an AR-HMD and the user’s sense of subjective perception of duration and temperature. In particular, we investigate two independent variables: the apparent temperature of the virtual stimuli presented to the participant, which could be hot or cold, and the location of the stimuli, which could be in direct contact with the user, in indirect contact with the user, or both in direct and indirect contact simultaneously. We investigate how these variables affect the users’ perception of duration and perception of body and environment temperature by having participants make prospective time estimations while observing the virtual stimulus and answering subjective questions regarding their body and environment temperatures. Our work confirms that temperature-associated virtual stimuli are capable of having significant effects on the users’ perception of temperature, and highlights a possible limitation in the current augmented reality technology in that no secondary effects on the users’ perception of duration were observed.

Current virtual reality (VR) head-mounted displays (HMDs) are characterized by a low angular resolution that makes it difficult to make out details, leading to reduced legibility of text and increased visual fatigue. Light-on-dark graphics modes, so-called "dark mode" graphics, are becoming more and more popular over a wide range of display technologies, and have been correlated with increased visual comfort and acuity, specifically when working in low-light environments, which suggests that they might provide significant advantages for VR HMDs.In this paper, we present a human-subject study investigating the correlations between the color mode and the ambient lighting with respect to visual acuity and fatigue on VR HMDs. We compare two color schemes, characterized by light letters on a dark background (dark mode), or dark letters on a light background (light mode), and show that the dark background in dark mode provides a significant advantage in terms of reduced visual fatigue and increased visual acuity in dim virtual environments on current HMDs. Based on our results, we discuss guidelines for user interfaces and applications.

Collaboration in a group has the potential to achieve more effective solutions for challenging problems, but collaboration per se is not an easy task, rather a stressful burden if the collaboration partners do not communicate well with each other. While Intelligent Virtual Assistants (IVAs), such as Amazon Alexa, are becoming part of our daily lives, there are increasing occurrences in which we collaborate with such IVAs for our daily tasks. Although IVAs can provide important support to users, the limited verbal interface in the current state of IVAs lacks the ability to provide effective non-verbal social cues, which is critical for improving collaborative performance and reducing task load.In this paper, we investigate the effects of IVA embodiment on collaborative decision making. In a within-subjects study, participants performed a desert survival task in three conditions: (1) performing the task alone, (2) working with a disembodied voice assistant, and (3) working with an embodied assistant. Our results show that both assistant conditions led to higher performance over when performing the task alone, but interestingly the reported task load with the embodied assistant was significantly lower than with the disembodied voice assistant. We discuss the findings with implications for effective and efficient collaborations with IVAs while also emphasizing the increased social presence and richness of the embodied assistant.

While research and development related to robotics has been going on for decades, the past decade in particular has seen a marked increase in related efforts, in part due to technological advances, increased technological accessibility and reliability, and increased commercial availability. What have come to be known as social robots are now being used to explore novel forms of human-robot interaction, to understand social norms, and to test expectations and human responses. To capture the contributions of these research efforts, identify the current trends, and future directions, we systematically review 10 years of research in the field of social robotics between 2008 and 2018, which includes 86 publications with 70 user studies. We classify the past work based on the research topics and application areas, and provide information about the publications, their user studies, and the capabilities of the social robots utilized. We also discuss selected papers in detail and outline overall trends. Based on these findings, we identify some areas of potential future research.

Human gaze awareness is important for social and collaborative interactions. Recent technological advances in augmented reality (AR) displays and sensors provide us with the means to extend collaborative spaces with real-time dynamic AR indicators of one's gaze, for example via three-dimensional cursors or rays emanating from a partner's head. However, such gaze cues are only as useful as the quality of the underlying gaze estimation and the accuracy of the display mechanism. Depending on the type of the visualization, and the characteristics of the errors, AR gaze cues could either enhance or interfere with collaborations. In this paper, we present two human-subject studies in which we investigate the influence of angular and depth errors, target distance, and the type of gaze visualization on participants' performance and subjective evaluation during a collaborative task with a virtual human partner, where participants identified targets within a dynamically walking crowd. First, our results show that there is a significant difference in performance for the two gaze visualizations ray and cursor in conditions with simulated angular and depth errors: the ray visualization provided significantly faster response times and fewer errors compared to the cursor visualization. Second, our results show that under optimal conditions, among four different gaze visualization methods, a ray without depth information provides the worst performance and is rated lowest, while a combination of a ray and cursor with depth information is rated highest. We discuss the subjective and objective performance thresholds and provide guidelines for practitioners in this field.

Redirected walking (RDW) enables virtual reality (VR) users to explore large virtual environments (VE) in confined tracking spaces by guiding users on different paths in the real world than in the VE. However, so far, spaces larger than typical room-scale setups of 5m × 5m are still required to allow infinitely straight walking, i. e., to prevent a subjective mismatch between real and virtual paths. This mismatch could in theory be reduced by interacting with the underlying brain activity. Transcranial direct-current stimulation (tDCS) presents a simply method able to modify ongoing cortical activity and excitability levels. Hence, this approach provides enormous potential to widen detection thresholds for RDW, and consequently reduce the above mentioned space requirements. In this paper, we conducted a psychophysical experiment using tDCS to evaluate detection thresholds for RDW gains. In the stimulation conditon 1.25 mA cathodal tDCS were applid over the prefrontal cortex (AF4 with Pz for the return current) for 20 minutes. TDCS failed to exert a significant overall effect on detection thresholds. However, for the highest gain only, path deviance was significantly modified by tDCS. In addition, subjectively reported disorientation was significantly lower during the tDCS as compared to the sham condition. Along the same line, oculomotor cyber sickness symptoms after the session were significantly decreased compared to baseline in tDCS, while there was no significant effect in sham. This work presents the first use of tDCS during virtual walking which provides new vistas for future research in the area of neurostimulation in VR.

Modern augmented reality (AR) head-mounted displays comprise a multitude of sensors that allow them to sense the environment around them. We have extended these capabilities by mounting two heat-wavelength infrared cameras to a Microsoft HoloLens, facilitating the acquisition of thermal data and enabling stereoscopic thermal overlays in the user's augmented view. The ability to visualize live thermal information opens several avenues of investigation on how that thermal awareness may affect a user's thermoception. We present a human-subject study, in which we simulated different temperature shifts using either heat vision overlays or 3D AR virtual effects associated with thermal cause-effect relationships (e.g., flames burn and ice cools). We further investigated differences in estimated temperatures when the stimuli were applied to either the user's body or their environment. Our analysis showed significant effects and first trends for the AR virtual effects and heat vision, respectively, on participants' temperature estimates for their body and the environment though with different strengths and characteristics, which we discuss in this paper.

Domestic animals have a long history of enriching human lives physically and mentally by filling a variety of different roles, such as service animals, emotional support animals, companions, and pets. Despite this, technological realizations of such animals in augmented reality (AR) are largely underexplored in terms of their behavior and interactions as well as effects they might have on human users' perception or behavior. In this paper, we describe a simulated virtual companion animal, in the form of a dog, in a shared AR space. We investigated its effects on participants' perception and behavior, including locomotion related to proxemics, with respect to their AR dog and other real people in the environment. We conducted a 2 by 2 mixed factorial human-subject study, in which we varied (i) the AR dog's awareness and behavior with respect to other people in the physical environment and (ii) the awareness and behavior of those people with respect to the AR dog. Our results show that having an AR companion dog changes participants' locomotion behavior, proxemics, and social interaction with other people who can or can not see the AR dog. We also show that the AR dog's simulated awareness and behaviors have an impact on participants' perception, including co-presence, animalism, perceived physicality, and dog's perceived awareness of the participant and environment. We discuss our findings and present insights and implications for the realization of effective AR animal companions.

Embodied virtual agents serving as patient simulators are widely used in medical training scenarios, ranging from physical patients to virtual patients presented via virtual and augmented reality technologies. Physical-virtual patients are a hybrid solution that combines the benefits of dynamic visuals integrated into a human-shaped physical form that can also present other cues, such as pulse, breathing sounds, and temperature. Sometimes in simulation the visuals and shape do not match. We carried out a human-participant study employing graduate nursing students in pediatric patient simulations comprising conditions associated with matching/non-matching of the visuals and shape.

Redirected and amplified head movements have the potential to provide more natural interaction with virtual environments (VEs) than using controller-based input, which causes large discrepancies between visual and vestibular self-motion cues and leads to increased VR sickness. However, such amplified head movements may also exacerbate VR sickness symptoms over no amplification. Several general methods have been introduced to reduce VR sickness for controller-based input inside a VE, including a popular vignetting method that gradually reduces the field of view.

Intelligent Virtual Agents (IVAs) are becoming part of our everyday life, thanks to artificial intelligence technology and Internet of Things devices. For example, users can control their connected home appliances through natural voice commands to the IVA. However, most current-state commercial IVAs, such as Amazon Alexa, mainly focus on voice commands and voice feedback, and lack the ability to provide non-verbal cues which are an important part of social interaction. Augmented Reality (AR) has the potential to overcome this challenge by providing a visual embodiment of the IVA. In this paper we investigate how visual embodiment and social behaviors influence the perception of the IVA. We hypothesize that a user's confidence in an IVA's ability to perform tasks is improved when imbuing the agent with a human body and social behaviors compared to the agent solely depending on voice feedback. In other words, an agent's embodied gesture and locomotion behavior exhibiting awareness of the surrounding real world or exerting influence over the environment can improve the perceived social presence with and confidence in the agent. We present a human-subject study, in which we evaluated the hypothesis and compared different forms of IVAs with speech, gesturing, and locomotion behaviors in an interactive AR scenario. The results show support for the hypothesis with measures of confidence, trust, and social presence. We discuss implications for future developments in the field of IVAs.

Conventional Intelligent Virtual Agents (IVAs) focus primarily on the visual and auditory channels for both the agent and the interacting human: the agent displays a visual appearance and speech as output, while processing the human's verbal and non-verbal behavior as input. However, some interactions, particularly those between a patient and healthcare provider, inherently include tactile components. We introduce an Intelligent Physical-Virtual Agent (IPVA) head that occupies an appropriate physical volume; can be touched; and via human-in-the-loop control can change appearance, listen, speak, and react physiologically in response to human behavior. Compared to a traditional IVA, it provides a physical affordance, allowing for more realistic and compelling human-agent interactions. In a user study focusing on neurological assessment of a simulated patient showing stroke symptoms, we compared the IPVA head with a high-fidelity touch-aware mannequin that has a static appearance. Various measures of the human subjects indicated greater attention, affinity for, and presence with the IPVA patient, all factors that can improve healthcare training.

The field of intelligent virtual agents (IVAs) has evolved immensely over the past 15 years, introducing new application opportunities in areas such as training, health care, and virtual assistants. In this survey paper, we provide a systematic review of the most influential user studies published in the IVA conference from 2001 to 2015 focusing on IVA development, human perception, and interactions. A total of 247 papers with 276 user studies have been classified and reviewed based on their contributions and impact. We identify the different areas of research and provide a summary of the papers with the highest impact. With the trends of past user studies and the current state of technology, we provide insights into future trends and research challenges.

Interaction tasks in virtual reality (VR) such as three-dimensional (3D) selection or manipulation of objects often suffer from reduced performance due to missing or different feedback provided by VR systems than during corresponding realworld interactions. Vibrotactile and auditory feedback have been suggested as additional perceptual cues complementing the visual channel to improve interaction in VR. However, it has rarely been shown that multimodal feedback improves performance or reduces errors during 3D object selection. Only little research has been conducted in the area of proximity-based multimodal feedback, in which stimulus intensities depend on spatiotemporal relations between input device and the virtual target object. In this paper, we analyzed the effects of unimodal and bimodal feedback provided through the visual, auditory and tactile modalities, while users perform 3D object selections in VEs, by comparing both binary and continuous proximity-based feedback. We conducted a Fitts' Law experiment and evaluated the different feedback approaches. The results show that the feedback types affect ballistic and correction phases of the selection movement, and significantly influence the user performance.

While research in the field of augmented reality (AR) has produced many innovative human-computer interaction techniques, some may produce physical and visual perceptions with unforeseen negative impacts on user performance. In a controlled human-subject study we investigated the effects of mismatched physical and visual perception on cognitive load and performance in an AR touching task by varying the physical fidelity (matching vs. non-matching physical shape) and visual mechanism (projector-based vs. HMD-based AR) of the representation. Participants touched visual targets on four corresponding physical-visual representations of a human head. We evaluated their performance in terms of touch accuracy, response time, and a cognitive load task requiring target size estimations during a concurrent (secondary) counting task. After each condition, participants completed questionnaires concerning mental, physical, and temporal demands; stress; frustration; and usability. Results indicated higher performance, lower cognitive load, and increased usability when participants touched a matching physical head-shaped surface and when visuals were provided by a projector from underneath.

In this paper, we investigate the effects of the physical influence of a virtual human (VH) in the context of face-to-face interaction in augmented reality (AR). In our study, participants played a tabletop game with a VH, in which each player takes a turn and moves their own token along the designated spots on the shared table. We compared two conditions as follows: the VH in the virtual condition moves a virtual token that can only be seen through AR glasses, while the VH in the physical condition moves a physical token as the participants do; therefore the VH's token can be seen even in the periphery of the AR glasses. For the physical condition, we designed an actuator system underneath the table. The actuator moves a magnet under the table which then moves the VH's physical token over the surface of the table. Our results indicate that participants felt higher co-presence with the VH in the physical condition, and participants assessed the VH as a more physical entity compared to the VH in the virtual condition. We further observed transference effects when participants attributed the VH's ability to move physical objects to other elements in the real world. Also, the VH's physical influence improved participants' overall experience with the VH. We discuss potential explanations for the findings and implications for future shared AR tabletop setups.

Immersive computer-generated environments (aka virtual reality, VR ) are limited by the physical space around them, e.g., enabling natural walking in VR is only possible by perceptually-inspired locomotion techniques such as redirected walking (RDW). We introduce a completely new approach to imperceptible position and orientation redirection that takes advantage of the fact that even healthy humans are functionally blind for circa ten percent of the time under normal circumstances due to motor processes preventing light from reaching the retina (such as eye blinks) or perceptual processes suppressing degraded visual information (such as blink-induced suppression). During such periods of missing visual input, change blindness occurs, which denotes the inability to perceive a visual change such as the motion of an object or self-motion of the observer. We show that this phenomenon can be exploited in VR by synchronizing the computer graphics rendering system with the human visual processes for imperceptible camera movements, in particular to implement position and orientation redirection. We analyzed human sensitivity to such visual changes with detection thresholds, which revealed that commercial off-the-shelf eye trackers and head-mounted displays suffice to translate a user by circa 4 -- 9 cm and rotate the user by circa 2 -- 5 degrees in any direction, which could be accumulated each time the user blinks. Moreover, we show the potential for RDW, whose performance could be improved by approximately 50% when using our technique.

Understanding real walking in virtual environments (VEs) is important for immersive experiences, allowing users to move through VEs in the most natural way. Previous studies have shown that basic implementations of real walking in virtual spaces, in which head-tracked movements are mapped isometrically to a VE, are not estimated as entirely natural. Instead, users estimate a virtual walking velocity as more natural when it is slightly increased compared to the user's physical locomotion. However, these findings have been reported in most cases only for young persons, e.g., students, whereas older adults are clearly underrepresented in such studies. Recently, virtual reality (VR) has received significant public and media attention. Therefore, it appears reasonable to assume that people at different ages will have access to VR, and might use this technology more and more in application scenarios such as rehabilitation or training. To better understand how people at different ages walk and perceive locomotion in VR, we have performed a study to investigate the effects of (non-)isometric mappings between physical movements and virtual motions in the VE on the walking biomechanics across generations, i.e., younger and older adults. Three primary domains (pace, base of support and phase) of spatio-temporal parameters were identified to evaluate gait performance. The results show that the older adults walked very similar in the real and VE in the pace and phasic domains, which differs from results found in younger adults. In contrast, the results indicate differences in terms of base of support domain parameters for both groups while walking within a VE and the real world. For non-isometric mappings, we found in both younger and older adults an increased divergence of gait parameters in all domains correlating with the up- or down-scaled velocity of visual self-motion feedback. The results provide important insights into the design of future VR applications for older adults in domains ranging from medicine and psychology to rehabilitation.

In 2008, Zhou et al. presented a survey paper summarizing the previous ten years of ISMAR publications, which provided invaluable insights into the research challenges and trends associated with that time period. Ten years later, we review the research that has been presented at ISMAR conferences since the survey of Zhou et al., at a time when both academia and the AR industry are enjoying dramatic technological changes. Here we consider the research results and trends of the last decade of ISMAR by carefully reviewing the ISMAR publications from the period of 2008-2017, in the context of the first ten years. The numbers of papers for different research topics and their impacts by citations were analyzed while reviewing them-which reveals that there is a sharp increase in AR evaluation and rendering research. Based on this review we offer some observations related to potential future research areas or trends, which could be helpful to AR researchers and industry members looking ahead.

In this paper, we investigate factors and issues related to human locomotion behavior and proxemics in the presence of a real or virtual human in augmented reality (AR). First, we discuss a unique issue with current-state optical see-through head-mounted displays, namely the mismatch between a small augmented visual field and a large unaugmented periphery, and its potential impact on locomotion behavior in close proximity of virtual content. We discuss a potential simple solution based on restricting the field of view to the central region, and we present the results of a controlled human-subject study. The study results show objective benefits for this approach in producing behaviors that more closely match those that occur when seeing a real human, but also some drawbacks in overall acceptance of the restricted field of view. Second, we discuss the limited multimodal feedback provided by virtual humans in AR, present a potential improvement based on vibrotactile feedback induced via the floor to compensate for the limited augmented visual field, and report results showing that benefits of such vibrations are less visible in objective locomotion behavior than in subjective estimates of co-presence. Third, we investigate and document significant differences in the effects that real and virtual humans have on locomotion behavior in AR with respect to clearance distances, walking speed, and head motions. We discuss potential explanations for these effects related to social expectations, and analyze effects of different types of behaviors including idle standing, jumping, and walking that such real or virtual humans may exhibit in the presence of an observer.

Our study investigates the effects of (non-)isometric mappings between physical movements and virtual motions in the virtual environment (VE) on walking biomechanics of older adults. Three primary domains (pace, base of support and phase) of spatio-temporal and temporo-phasic parameters were used to evaluate gait performance. Our results show similar results in pace and phasic domains when older adults walk in the VE in the isometric mapping condition compared to the corresponding parameters in the real world. We found significant differences in base of support for our user group between walking in the VE and real world. For non-isometric mappings we found an increased divergence of gait parameters in all domains correlating with the up-or down-scaled velocity of visual self-motion feedback.

Redirected walking (RDW) promises to allow near-natural walking in an infinitely large virtual environment (VE) by subtle manipulations of the virtual camera. Previous experiments showed that a physical radius of at least 22 meters is required for undetectable RDW. However, we found that it is possible to decrease this radius and to apply RDW to room-scale VR, i. e., up to approximately 5m × 5m. This is done by using curved paths in the Ve instead of straight paths, and by coupling them together in a way that enables continuous walking. Furthermore, the corresponding paths in the real world are laid out in a way that fits perfectly into room-scale VR. In this research demo, users can experience RDW in a room-scale head-mounted display VR setup and explore a VE of approximately 25m × 25m.

We investigate the effect of vibrotactile feedback delivered to one's feet in an immersive virtual environment (IVE). In our study, participants observed a virtual environment where a virtual human (VH) walked toward the participants and paced back and forth within their social space. We compared three conditions as follows: participants in the “Sound” condition heard the footsteps of the VH; participants in the “Vibration” condition experienced the vibration of the footsteps along with the sounds; while participants in the “Mute” condition were not exposed to sound nor vibrotactile feedback. We found that the participants in the “Vibration” condition felt a higher social presence with the VH compared to those who did not feel the vibration. The participants in the “Vibration” condition also exhibited greater avoidance behavior while facing the VH and when the VH invaded their personal space.

Augmented reality (AR) enables the illusion of computer-generated virtual objects and humans co-existing with us in the real world. Virtual humans (VHs) in AR can further induce an illusion of physicality in the real world due to their form of presentation and their behavior, such as showing awareness of their surroundings. However, certain behaviors can cause a conflict that breaks this illusion, for example, when we see a VH passing through a physical object.

Abstract In augmented reality, people can feel the illusion of virtual humans (VHs) integrated into a real (physical) space. However, affordances of the real world and virtual contents might conflict, for example, when the VHs and real objects “collide” by occupying the same space. This implausible conflict can cause a break in presence in real–virtual human interactions. In this paper, we address an effort to avoid this conflict by maintaining the VH's spatial and behavioral coherence with respect to the physical objects or events (e.g., natural occlusions and appropriate help‐requesting behaviors to avoid implausible physical–virtual collisions). We present a human subject experiment examining the effects of the physical–virtual coherence on human perceptions, such as social/copresence and behaviors with the VH. The basic ideas, experimental design, and results supporting the benefit of the VH's spatial and behavioral coherence are presented and discussed.

Walking constitutes the predominant form of self-propelled movement from one geographic location to another in our real world. Likewise, walking in virtual environments (VEs) is an essential part of a users experience in many application domains requiring a high degree of interactivity. However, researchers and practitioners often observe that basic implementations of virtual walking, in which head-tracked movements are mapped isometrically to a VE are not estimated as entirely natural. Instead, users estimate a virtual walking velocity as more natural when it is slightly increased compared to the users physical body movement. In this article, we investigate the effects of such nonisometric mappings between physical movements and virtual motions in the VE on walking velocity and biomechanics of the gait cycle. Therefore, we performed an experiment in which we measured and analyzed parameters of the biomechanics of walking under conditions with isometric as well as nonisometric mappings. Our results show significant differences in most gait parameters when walking in the VE in the isometric mapping condition compared to the corresponding parameters in the real world. For nonisometric mappings we found an increased divergence of gait parameters depending on the velocity of visual self-motion feedback. The results revealed a symmetrical effect of gait detriments for up- or down-scaled virtual velocities, which we discuss in the scope of the previous findings.

Redirected walking (RDW) promises to allow near-natural walking in an infinitely large virtual environment (VE) by subtle manipulations of the virtual camera. Previous experiments analyzed the human sensitivity to RDW manipulations by focusing on the worst-case scenario, in which users walk perfectly straight ahead in the VE, whereas they are redirected on a circular path in the real world. The results showed that a physical radius of at least 22 meters is required for undetectable RDW. However, users do not always walk exactly straight in a VE. So far, it has not been investigated how much a physical path can be bent in situations in which users walk a virtual curved path instead of a straight one. Such curved walking paths can be often observed, for example, when users walk on virtual trails, through bent corridors, or when circling around obstacles. In such situations the question is not, whether or not the physical path can be bent, but how much the bending of the physical path may vary from the bending of the virtual path. In this article, we analyze this question and present redirection by means of bending gains that describe the discrepancy between the bending of curved paths in the real and virtual environment. Furthermore, we report the psychophysical experiments in which we analyzed the human sensitivity to these gains. The results reveal encouragingly wider detection thresholds than for straightforward walking. Based on our findings, we discuss the potential of curved walking and present a first approach to leverage bent paths in a way that can provide undetectable RDW manipulations even in room-scale VR.

It is known for decades that users tend to significantly underestimate or overestimate distances or speed in immersive virtual environments (IVEs) compared to corresponding judgments in the real world. Although several factors have been identified in the past that could explain small portions of this effect, the main causes of these perceptual discrepancies still remain elusive. One of the factors that has received less attention in the literature is the amount of blur presented in the visual imagery, for example, when using a head-mounted display (HMD).

Current virtual reality (VR) technologies have enormous potential to allow humans to experience computer-generated immersive virtual environments (IVEs). Many of these IVEs support near-natural audiovisual stimuli similar to the stimuli generated in our physical world. However, decades of VR research have been devoted to exploring and understand differences between perception and action in such IVEs compared to real-world perception and action. Although, significant differences have been revealed for spatiotemporal perception between IVEs and the physical world such as distance underestimation, there is still a scarcity of knowledge about the reasons for such perceptual discrepancies, in particular regarding the perception of temporal durations in IVEs. In this article, we explore the effects of manipulated zeitgebers, cognitive load and immersion on time estimation as yet unexplored factors of spatiotemporal perception in IVEs. We present an experiment in which we analyze human sensitivity to temporal durations while experiencing an immersive head-mounted display (HMO) environment. We found that manipulations of external zeitgebers caused by a natural or unnatural movement of the virtual sun had a significant effect on time judgments. Moreover, using the dual-task paradigm the results show that increased spatial and verbal cognitive load resulted in a significant shortening of judged time as well as an interaction with the external zeitgebers. Finally, we discuss the implications for the design of near-natural computer-generated virtual worlds.

In this paper, we investigate obstacle avoidance behavior during real walking in a large immersive projection setup. We analyze the walking behavior of users when avoiding real and virtual static obstacles. In order to generalize our study, we consider both anthropomorphic and inanimate objects, each having his virtual and real counterpart. The results showed that users exhibit different locomotion behaviors in the presence of real and virtual obstacles, and in the presence of anthropomorphic and inanimate objects. Precisely, the results showed a decrease of walking speed as well as an increase of the clearance distance (i. e., the minimal distance between the walker and the obstacle) when facing virtual obstacles compared to real ones. Moreover, our results suggest that users act differently due to their perception of the obstacle: users keep more distance when the obstacle is anthropomorphic compared to an inanimate object and when the orientation of anthropomorphic obstacle is from the profile compared to a front position. We discuss implications on future large shared immersive projection spaces.

When walking within an immersive projection environment, accommodation distance, parallax and angular resolution vary according to the distance between the user and the projection walls which can influence spatial perception. As CAVE-like virtual environments get bigger, accurate spatial perception within the projection setup becomes increasingly important for application domains that require the user to be able to naturally explore a virtual environment by moving through the physical interaction space. In this paper we describe an experiment which analyzes how distance estimation is biased when the distance to the screen and parallax vary. The experiment was conducted in a large immersive projection setup with up to ten meter interaction space. The results showed that both the screen distance and parallax have a strong asymmetric effect on distance judgments. We found an increased distance underestimation for positive parallax conditions. In contrast, we found less distance overestimation for negative and zero parallax conditions. We conclude the paper discussing the results with view on future large immersive projection environments.

Redirected walking allows users to walk through a large-scale immersive virtual environment (IVE) while physically remaining in a reasonably small workspace. Therefore, manipulations are applied to virtual camera motions so that the user's self-motion in the virtual world differs from movements in the real world. Previous work found that the human perceptual system tolerates a certain amount of inconsistency between proprioceptive, vestibular and visual sensation in IVEs, and even compensates for slight discrepancies with recalibrated motor commands. Experiments showed that users are not able to detect an inconsistency if their physical path is bent with a radius of at least 22 meters during virtual straightforward movements. If redirected walking is applied in a smaller workspace, manipulations become noticeable, but users are still able to move through a potentially infinitely large virtual world by walking. For this semi-natural form of locomotion, the question arises if such manipulations impose cognitive demands on the user, which may compete with other tasks in IVEs for finite cognitive resources. In this article we present an experiment in which we analyze the mutual influence between redirected walking and verbal as well as spatial working memory tasks using a dual-tasking method. The results show an influence of redirected walking on verbal as well as spatial working memory tasks, and we also found an effect of cognitive tasks on walking behavior. We discuss the implications and provide guidelines for using redirected walking in virtual reality laboratories.

A large body of literature has analyzed differences between perception in the real world and virtual environments (VE) in terms of space, distance and speed perception. So far, no empirical data has been collected for time misperception in immersive VEs to our knowledge. However, there is evidence that time perception can deviate from veridical judgments, for instance, due to visual or auditive stimulation related to motion misperception. In this work we evaluate time perception during walking motions with a pilot study in an immersive head-mounted display (HMD) environment. Significant differences between time judgments in the real and virtual environment could not be observed.

Locomotion is one of the most fundamental processes in the real world, and its consideration in immersive virtual environments (IVEs) is of major importance for many application domains requiring immersive walkthroughs. From a simple physics perspective, such self-motion can be defined by the three components speed, distance, and time. Determining motions in the frame of reference of a human observer imposes a significant challenge to the perceptual processes in the human brain, and the resulting speed, distance, and time percepts are not always veridical. In previous work in the area of IVEs, these components were evaluated in separate experiments, i. e., using largely different hardware, software and protocols.

One major benefit of wearable computers is that users can naturally move and explore computer-mediated realities. However, researchers often observe that users' space and motion perception severely differ in such environments compared to the real world, an effect that is often attributed to slight discrepancies in sensory cues, for instance, caused by tracking inaccuracy or system latency. This is particularly true for virtual reality (VR), but such conflicts are also inherent to augmented reality (AR) technologies. Although, head-worn displays will become more and more available soon, the effects on motion perception have rarely been studied, and techniques to modify self-motion in AR environments have not been leveraged so far. In this paper we introduce the concept of computer-mediated optic flow, and analyze its effects on self-motion perception in AR environments. First, we introduce different techniques to modify optic flow patterns and velocity. We present a psychophysical experiment which reveals differences in self-motion perception with a video see-through head-worn display compared to the real-world viewing condition. We show that computer-mediated optic flow has the potential to make a user perceive self-motion as faster or slower than it actually is, and we discuss its potential for future AR setups.

Recent developments in the fields of display technology provide new possibilities for engaging users in interactive exploration of three-dimensional (3D) virtual environments (VEs). Tracking technologies such as the Microsoft Kinect and emerging multi-touch interfaces enable inexpensive and low-maintenance interactive setups while providing portable solutions for engaging presentations and exhibitions. In this poster we describe an extension of the smARTbox, which is a responsive touch-enabled stereoscopic out-of-the-box technology for interactive setups. We extended the smARTbox by making the entire setup portable, which provides a new interaction experience, when exploring 3D data sets. The portable tracked multi-touch interface supports two different interaction paradigms: exploration by multi-touch gestures as well a s exploration by lateral movements of the entire setup. Hence, typical gestures supporting rotation and panning can be implemented via multi-touch gestures, but also via actual movements of the setup.

Accurate perception of size and distance in a three-dimensional virtual environment is important for many applications. However, several experiments have revealed that spatial perception of virtual environments often deviates from the real world, even when the virtual scene is modeled as an accurate replica of a familiar physical environment. While previous research has elucidated various factors that can facilitate perceptual shifts, the effects of geometric rendering parameters on spatial cues are still not well understood.

This article presents an analysis of using multiple Microsoft Kinects to track users in a VR system. More specifically, we analyse the capability of Kinects to track infrared points for use in VR applications. Multiple Kinect sensors may serve as a low cost and affordable means to track position information across a large lab space in applications where precise location tracking is not necessary. We present our findings and analysis of the tracking range of a Kinect sensor in situations in which multiple Kinects are present. Overall, the Kinect sensor works well for this application and in lieu of more expensive options, the Kinect sensors may be a viable option for very low-cost tracking in VR applications.

Natural walking can provide a compelling experience in immersive virtual environments, but it remains an implementation challenge due to the physical space constraints imposed on the size of the virtual world. The use of redirection techniques is a promising approach that relaxes the space requirements of natural walking by manipulating the user's route in the virtual environment, causing the real world path to remain within the boundaries of the physical workspace. In this paper, we present and apply a novel taxonomy that separates redirection techniques according to their geometric flexibility versus the likelihood that they will be noticed by users. Additionally, we conducted a user study of three reorientation techniques, which confirmed that participants were less likely to experience a break in presence when reoriented using the techniques classified as subtle in our taxonomy. Our results also suggest that reorientation with change blindness illusions may give the impression of exploring a more expansive environment than continuous rotation techniques, but at the cost of negatively impacting spatial knowledge acquisition.

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.

Motion perception in immersive virtual environments significantly differs from the real world. For example, previous work has shown that users tend to underestimate travel distances in virtual environments (VEs). As a solution to this problem, researchers proposed to scale the mapped virtual camera motion relative to the tracked real-world movement of a user until real and virtual motion are perceived as equal, i.e., real-world movements could be mapped with a larger gain to the VE in order to compensate for the underestimation. However, introducing discrepancies between real and virtual motion can become a problem, in particular, due to misalignments of both worlds and distorted space cognition. In this paper, we describe a different approach that introduces apparent self-motion illusions by manipulating optic flow fields during movements in VEs. These manipulations can affect self-motion perception in VEs, but omit a quantitative discrepancy between real and virtual motions. In particular, we consider to which regions of the virtual view these apparent self-motion illusions can be applied, i.e., the ground plane or peripheral vision. Therefore, we introduce four illusions and show in experiments that optic flow manipulation can significantly affect users' self-motion judgments. Furthermore, we show that with such manipulations of optic flow fields the underestimation of travel distances can be compensated.

Head-mounted displays (HMDs) allow users to observe virtual environments (VEs) from an egocentric perspective. However, several experiments have provided evidence that egocentric distances are perceived as compressed in VEs relative to the real world. Recent experiments suggest that the virtual view frustum set for rendering the VE has an essential impact on the user's estimation of distances. In this article we analyze if distance estimation can be improved by calibrating the view frustum for a given HMD and user. Unfortunately, in an immersive virtual reality (VR) environment, a full per user calibration is not trivial and manual per user adjustment often leads to mini- or magnification of the scene. Therefore, we propose a novel per user calibration approach with optical see-through displays commonly used in augmented reality (AR). This calibration takes advantage of a geometric scheme based on 2D point - 3D line correspondences, which can be used intuitively by inexperienced users and requires less than a minute to complete. The required user interaction is based on taking aim at a distant target marker with a close marker, which ensures non-planar measurements covering a large area of the interaction space while also reducing the number of required measurements to five. We found the tendency that a calibrated view frustum reduced the average distance underestimation of users in an immersive VR environment, but even the correctly calibrated view frustum could not entirely compensate for the distance underestimation effects.

Recent developments in the area of touch and display technologies have suggested to combine multi-touch systems and stereoscopic visualization. Stereoscopic perception requires each eye to see a slightly different perspective of the same scene, which results in two distinct projections on the display. Thus, if the user wants to select a 3D stereoscopic object in such a setup, the question arises where she would touch the 2D surface to indicate the selection. A user may apply different strategies, for instance touching the midpoint between the two projections, or touching one of them.

Motion perception in immersive virtual reality environments significantly differs from the real world. For example, previous work has shown that users tend to underestimate travel distances in immersive virtual environments (VEs). As a solution to this problem, some researchers propose to scale the mapped virtual camera motion relative to the tracked real-world movement of a user until real and virtual motion appear to match, i. e., real-world movements could be mapped with a larger gain to the VE in order to compensate for the underestimation. Although this approach usually results in more accurate self-motion judgments by users, introducing discrepancies between real and virtual motion can become a problem, in particular, due to misalignments of both worlds and distorted space cognition. In this paper we describe a different approach that introduces apparent self-motion illusions by manipulating optic flow fields during movements in VEs. These manipulations can affect self-motion perception in VEs, but omit a quantitative discrepancy between real and virtual motions. We introduce four illusions and show in experiments that optic flow manipulation can significantly affect users' self-motion judgments. Furthermore, we show that with such manipulation of optic flow fields the underestimation of travel distances can be compensated.

Computer graphics systems provide sophisticated means to render virtual 3D space to 2D display surfaces by applying planar geometric projections. In a realistic viewing condition the perspective applied for rendering should appropriately account for the viewer's location relative to the image. As a result, an observer would not be able to distinguish between a rendering of a virtual environment on a computer screen and a view “through” the screen at an identical real-world scene. Until now, little effort has been made to identify perspective projections which cause human observers to judge them to be realistic. In this article we analyze observers' awareness of perspective distortions of virtual scenes displayed on a computer screen. These distortions warp the virtual scene and make it differ significantly from how the scene would look in reality. We describe psychophysical experiments that explore the subject's ability to discriminate between different perspective projections and identify projections that most closely match an equivalent real scene. We found that the field of view used for perspective rendering should match the actual visual angle of the display to provide users with a realistic view. However, we found that slight changes of the field of view in the range of 10-20% for two classes of test environments did not cause a distorted mental image of the observed models.

In visual perception, change blindness describes the phenomenon that persons viewing a visual scene may apparently fail to detect significant changes in that scene. These phenomena have been observed in both computer-generated imagery and real-world scenes. Several studies have demonstrated that change blindness effects occur primarily during visual disruptions such as blinks or saccadic eye movements. However, until now the influence of stereoscopic vision on change blindness has not been studied thoroughly in the context of visual perception research. In this paper, we introduce change blindness techniques for stereoscopic virtual reality (VR) systems, providing the ability to substantially modify a virtual scene in a manner that is difficult for observers to perceive. We evaluate techniques for semiimmersive VR systems, i.e., a passive and active stereoscopic projection system as well as an immersive VR system, i.e., a head-mounted display, and compare the results to those of monoscopic viewing conditions. For stereoscopic viewing conditions, we found that change blindness phenomena occur with the same magnitude as in monoscopic viewing conditions. Furthermore, we have evaluated the potential of the presented techniques for allowing abrupt, and yet significant, changes of a stereoscopically displayed virtual reality environment.

The display units integrated in today's head-mounted displays (HMDs) provide only a limited field of view (FOV) to the virtual world. In order to present an undistorted view to the virtual environment (VE), the perspective projection used to render the VE has to be adjusted to the limitations caused by the HMD characteristics. In particular, the geometric field of view (GFOV), which defines the virtual aperture angle used for rendering of the 3D scene, is set up according to the display field of view (DFOV). A discrepancy between these two fields of view distorts the geometry of the VE in a way that either minifies or magnifies the imagery displayed to the user. It has been shown that this distortion has the potential to affect a user's perception of the virtual space, sense of presence, and performance on visual search tasks. In this paper, we analyze the user's perception of a VE displayed in a HMD, which is rendered with different GFOVs. We introduce a psychophysical calibration method to determine the HMD's actual field of view, which may vary from the nominal values specified by the manufacturer. Furthermore, we conducted two experiments to identify perspective projections for HMDs, which are identified as natural by subjects--even if these perspectives deviate from the perspectives that are inherently defined by the DFOV. In the first experiment, subjects had to adjust the GFOV for a rendered virtual laboratory such that their perception of the virtual replica matched the perception of the real laboratory, which they saw before the virtual one. In the second experiment, we displayed the same virtual laboratory, but restricted the viewing condition in the real world to simulate the limited viewing condition in a HMD environment. We found that subjects evaluate a GFOV as natural when it is larger than the actual DFOV of the HMD--in some cases up to 50 percent--even when subjects viewed the real space with a limited field of view.

In visual perception, change blindness describes the phenomenon that persons viewing a visual scene may apparently fail to detect significant changes in that scene. These phenomena have been observed in both computer generated imagery and real-world scenes. Several studies have demonstrated that change blindness effects occur primarily during visual disruptions such as blinks or saccadic eye movements. However, until now the influence of stereoscopic vision on change blindness has not been studied thoroughly in the context of visual perception research. In this paper we introduce change blindness techniques for stereoscopic projection systems, providing the ability to substantially modify a virtual scene in a manner that is difficult for observers to perceive. We evaluate techniques for passive and active stereoscopic viewing and compare the results to those of monoscopic viewing conditions. For stereoscopic viewing conditions, we found that change blindness phenomena occur with the same magnitude as in monoscopic viewing conditions. Furthermore, we have evaluated the potential of the presented techniques for allowing abrupt, and yet significant, changes of a stereoscopically displayed virtual reality environment.

Physical characteristics and constraints of today's head-mounted displays (HMDs) often impair interaction in immersive virtual environments (VEs). For instance, due to the limited field of view (FOV) subtended by the display units in front of the user's eyes more effort is required to explore a VE by head rotations than for exploration in the real world.

In immersive virtual environments (IVEs), users can control their virtual viewpoint by moving their tracked head and walking through the real world. Usually, movements in the real world are mapped one-to-one to virtual camera motions. With redirection techniques, the virtual camera is manipulated by applying gains to user motion so that the virtual world moves differently than the real world. Thus, users can walk through large-scale IVEs while physically remaining in a reasonably small workspace. In psychophysical experiments with a two-alternative forced-choice task, we have quantified how much humans can unknowingly be redirected on physical paths that are different from the visually perceived paths. We tested 12 subjects in three different experiments: (E1) discrimination between virtual and physical rotations, (E2) discrimination between virtual and physical straightforward movements, and (E3) discrimination of path curvature. In experiment E1, subjects performed rotations with different gains, and then had to choose whether the visually perceived rotation was smaller or greater than the physical rotation. In experiment E2, subjects chose whether the physical walk was shorter or longer than the visually perceived scaled travel distance. In experiment E3, subjects estimate the path curvature when walking a curved path in the real world while the visual display shows a straight path in the virtual world. Our results show that users can be turned physically about 49 percent more or 20 percent less than the perceived virtual rotation, distances can be downscaled by 14 percent and upscaled by 26 percent, and users can be redirected on a circular arc with a radius greater than 22 m while they believe that they are walking straight.

In order to increase a user's sense of presence in an artificial environment some researchers propose a gradual transition from reality to the virtual world instead of immersing users into the virtual world directly. One approach is to start the VR experience in a virtual replica of the physical space to accustom users to the characteristics of VR, e.g., latency, reduced field of view or tracking errors, in a known environment. Although this procedure is already applied in VR demonstrations, until now it has not been verified whether the usage of such a transitional environment - as transition between real and virtual environment - increases someone's sense of presence. We have observed subjective, physiological and behavioral reactions of subjects during a fully-immersive flight phobia experiment under two different conditions: the virtual flight environment was displayed immediately, or subjects visited a transitional environment before entering the virtual flight environment. We have quantified to what extent a gradual transition to the VE via a transitional environment increases the level of presence. We have found that subjective responses show significantly higher scores for the user's sense of presence, and that subjects' behavioral reactions change when a transitional environment is shown first. Considering physiological reactions, no significant difference could be found.

The display units integrated in todays head-mounted displays (HMDs) provide only a limited field of view (FOV) to the virtual world. In order to present an undistorted view to the virtual environment (VE), the perspective projection used to render the VE has to be adjusted to the limitations caused by the HMD characteristics. In particular, the geometric field of view (GFOV), which defines the virtual aperture angle used for rendering of the 3D scene, is set up according to the display's field of view. A discrepancy between these two fields of view distorts the geometry of the VE in a way that either minifies or magnifies the imagery displayed to the user. Discrepancies between the geometric and physical FOV causes the imagery to be minified or magnified. This distortion has the potential to negatively or positively affect a user's perception of the virtual space, sense of presence, and performance on visual search tasks.

Traveling through immersive virtual environments (IVEs) by means of real walking is an important activity to increase naturalness of VR-based interaction. However, the size of the virtual world often exceeds the size of the tracked space so that a straightforward implementation of omni-directional and unlimited walking is not possible. Redirected walking is one concept to solve this problem of walking in IVEs by inconspicuously guiding the user on a physical path that may differ from the path the user visually perceives. When the user approaches a virtual object she can be redirected to a real proxy object that is registered to the virtual counterpart and provides passive haptic feedback. In such passive haptic environments, any number of virtual objects can be mapped to proxy objects having similar haptic properties, e.g., size, shape and texture. The user can sense a virtual object by touching its real world counterpart. Redirecting a user to a registered proxy object makes it necessary to predict the user's intended position in the IVE. Based on this target position we determine a path through the physical space such that the user is guided to the registered proxy object. We present a taxonomy of possible redirection techniques that enable user guidance such that inconsistencies between visual and proprioceptive stimuli are imperceptible. We describe how a user's target in the virtual world can be predicted reliably and how a corresponding real-world path to the registered proxy object can be derived.

In this paper we introduce a virtual locomotion system that allows navigation within any large-scale virtual environment (VE) by real walking. In contrast to the work of Razzaque et al. (2001) we have developed generic redirected walking concepts by combining motion compression, i. e., scaling the real distance users walk, rotation gains, which make the real turns smaller or larger, and curvature gains, which bend the user's walking direction such that s/he walks on a curve. Furthermore, we introduce the new concept of dynamic passive haptics which extends passive haptics (Insko et al., 2001; Kohli et al., 2005) in such a way that any number of virtual objects can be sensed by means of real proxy objects having similar haptic capabilities, i. e., size, shape and surface structure. We have evaluated these concepts and explain technical details regarding their integration into legacy 3D graphics applications.

Redirected walking allows users to walk through large-scale immersive virtual environments (IVEs) while physically remaining in a reasonably small workspace by intentionally injecting scene motion into the IVE. In a constant stimuli experiment with a twoalternative-forced-choice task we have quantified how much humans can unknowingly be redirected on virtual paths which are different from the paths they actually walk. 18 subjects have been tested in four different experiments: (E1a) discrimination between virtual and physical rotation, (E1b) discrimination between two successive rotations, (E2) discrimination between virtual and physical translation, and discrimination of walking direction (E3a) without and (E3b) with start-up. In experiment E1a subjects performed rotations to which different gains have been applied, and then had to choose whether or not the visually perceived rotation was greater than the physical rotation. In experiment E1b subjects discriminated between two successive rotations where different gains have been applied to the physical rotation. In experiment E2 subjects chose if they thought that the physical walk was longer than the visually perceived scaled travel distance. In experiment E3a subjects walked a straight path in the IVE which was physically bent to the left or to the right, and they estimate the direction of the curvature. In experiment E3a the gain was applied immediately, whereas the gain was applied after a start-up of two meters in experiment E3b. Our results show that users can be turned physically about 68% more or 10 % less than the perceived virtual rotation, distances can be up- or down-scaled by 22%, and users can be redirected on an circular arc with a radius greater than 24 meters while they believe they are walking straight.

In this paper we introduce new user interface concepts for fish tank virtual reality (VR) systems based on autostereoscopic (AS) display technologies. Such AS displays allow to view stereoscopic content without requiring special glasses. Unfortunately, until now simultaneous monoscopic and stereoscopic display was not possible. Hence prior work on fish tank VR systems focussed either on 2D or 3D interactions. In this paper we introduce so called interscopic interaction concepts providing an improved working experience, which enable great potentials in terms of the interaction between 2D elements, which may be displayed either in monoscopic or stereoscopic, e.g., GUI items, and the 3D virtual environment usually displayed stereoscopically. We present a framework which is based on a software layer between the operating system and its graphical user interface supporting the display of both mono- as well as stereoscopic content in arbitrary regions of an autostereoscopic display. The proposed concepts open up new vistas for the interaction in environments where essential parts of the GUI are displayed monoscopically and other parts are rendered stereoscopically. We address some essential issues of such fish tank VR systems and introduce intuitive interaction concepts which we have realized

Figure 1: Using hybrid travel approaches (left) in outdoor pedestrian mode using scaled user movements in a 3D building evaluation system, (middle) in indoor pedestrian mode displayed in Google Earth, and (right) in outdoor mode in Microsoft Virtual Earth. In this paper we present hybrid traveling concepts that enable users to navigate immersively through 3D geospatial environments displayed by arbitrary applications such as Google Earth or Microsoft Virtual Earth. We propose a framework which allows to integrate virtual reality (VR) based interaction devices and concepts into such applications that do not support VR technologies natively. In our proposed setup the content displayed by a geospatial application is visualized stereoscopically on a head-mounted display (HMD) for immersive exploration. The user’s body is tracked in order to support natural traveling through the VE via a walking metaphor. Since the VE usually exceeds the dimension of the area in which the user can be tracked, we propose different strategies to map the user’s movement into the virtual world intuitively. Moreover, commonly available devices and interaction techniques are presented for both-handed interaction to enrich the navigation process.