In data analysis, scatterplots serve as an initial tool for exploring the relationships between two or three attributes. While scatterplot matrices (SPLOMs) display every attribute combination through numerous 2D scatterplots to show a concise overview of a multivariate dataset, this approach is not directly suitable for 3D scatterplots due to visual clutter. Since research has shown that immersive virtual environments can enhance data analysis compared to traditional 2D desktop setups – especially for spatial analysis tasks – we propose an interactive system, called SPLOCIS, that makes use of virtual reality to enable users to interactively filter and select 3D scatter-plots from all possible attribute combinations. Our user study, combining both qualitative and quantitative results, demonstrates that SPLOCIS is a particularly novel and stimulating approach to work with multivariate data in immersive environments. It enables solving classic data exploration tasks in an efficient and accurate way, while not imposing unexpectedly high task loads. Moreover, our findings provide promising suggestions for further developments.

Traditional target-selection-based teleportation depends on the intersection of a (curved) ray with the scene's geometry, which limits navigation to points on the ground, restricting users' navigational freedom. While previous techniques exist that permit mid-air target selection, they are not optimal for transitioning between air and ground navigation, leading to inaccurate or lengthy interaction sequences. In this paper, we introduce SATOR, a new 3D teleportation technique designed to enable efficient and accurate navigation to both ground and mid-air targets by combining and enhancing previous approaches. Informed by the literature, we implemented four different parametrizations of our technique and compared them to a previously published technique that also enables both ground and mid-air target selection. Our user study with 30 participants indicates that SATOR is more efficient, accurate, and easier to use than the baseline. As a result, SATOR effectively helps users get an overview of the environment, observe features at different heights, or maneuver quickly around larger obstacles.

Target-selection-based teleportation is one of the most widely used and researched travel techniques in immersive virtual environments, requiring the user to specify a target location with a selection ray before being transported there. This work explores the influence of the maximum reach of the parabolic selection ray, modeled by different emission velocities of the projectile motion equation, and compares the resulting teleportation performance to a straight ray as the baseline. In a user study with 60 participants, we asked participants to teleport as far as possible while still remaining within accuracy constraints to understand how the theoretical implications of the projectile motion equation apply to a realistic VR use case. We found that a projectile emission velocity of $14 \frac{m}{s}$14ms (resulting in a maximal reach of $\text{21.52 m}$21.52m) offered the best trade-off between selection distance and accuracy, with an inferior performance of the straight ray. Our results demonstrate the necessity to carefully set and report the projectile emission velocity in future work, as it was shown to directly influence user-selected distance, selection errors, and controller height during selection.

The Simulator Sickness Questionnaire (SSQ) has become a standard tool for quantifying the severity and distribution of discomfort symptoms in virtual reality (VR) research. Despite its straightforward administration, the use of the SSQ also comes with significant challenges, including response subjectivity, strict threshold values based on a military reference population, and confounding factors influencing the results. To demonstrate the adverse interplay of these issues, we asked three cohorts of students to fill in a SSQ after having attended a 90-minute lecture of our teaching program. Although students were not exposed to any form of VR experience, the resulting SSQ scores were indistinguishable from VR studies and extended far beyond the originally defined threshold of a "bad simulator", with 88.1% of TS scores being larger and 25.4% even exceeding thrice this value. We compare our results to alternative scoring systems of the SSQ proposed in the literature and suggest implications for future experimental designs involving the quantification of sickness symptoms. In summary, our results motivate to exert caution when interpreting the results of the SSQ in the context of a VR study; participants might just have attended a lecture prior to the experiment.

Collaborative work in social virtual reality often requires an interplay of loosely coupled collaboration from different virtual locations and tightly coupled face-to-face collaboration. Without appropriate system mediation, however, transitioning between these phases requires high navigation and coordination efforts. In this paper, we present an interaction system that allows collaborators in virtual reality to seamlessly switch between different collaboration models known from related work. To this end, we present collaborators with functionalities that let them work on individual sub-tasks in different virtual locations, consult each other using asymmetric interaction patterns while keeping their current location, and temporarily or permanently join each other for face-to-face interaction. We evaluated our methods in a user study with 32 participants working in teams of two. Our quantitative results indicate that delegating the target selection process for a long-distance teleport significantly improves placement accuracy and decreases task load within the team. Our qualitative user feedback shows that our system can be applied to support flexible collaboration. In addition, the proposed interaction sequence received positive evaluations from teams with varying VR experiences.

Working with scatterplots is a classic everyday task for data analysts, which gets increasingly complex the more plots are required to form an understanding of the underlying data. To help analysts retrieve relevant plots more quickly when they are needed, immersive virtual environments (iVEs) provide them with the option to freely arrange scatterplots in the 3D space around them. In this paper, we investigate the impact of different virtual environments on the users' ability to quickly find and retrieve individual scatterplots from a larger collection. We tested three different scenarios, all having in common that users were able to position the plots freely in space according to their own needs, but each providing them with varying numbers of landmarks serving as visual cues: an Empty scene as a baseline condition, a single landmark condition with one prominent visual cue being a Desk, and a multiple landmarks condition being a virtual Office. Results from a between-subject investigation with 45 participants indicate that the time and effort users invest in arranging their plots within an iVE had a greater impact on memory performance than the design of the iVE itself. We report on the individual arrangement strategies that participants used to solve the task effectively and underline the importance of an active arrangement phase for supporting the spatial memorization of scatterplots in iVEs.

Collaborative work in large virtual environments often requires transitions from loosely-coupled collaboration at different locations to tightly-coupled collaboration at a common meeting point. Inspired by prior work on the continuum between these extremes, we present two novel interaction techniques designed to share spatial context while collaborating over large virtual distances. The first method replicates the familiar setup of a video conference by providing users with a virtual tablet to share video feeds with their peers. The second method called PASCAL (Parallel Avatars in a Shared Collaborative Aura Link) enables users to share their immediate spatial surroundings with others by creating synchronized copies of it at the remote locations of their collaborators. We evaluated both techniques in a within-subject user study, in which 24 participants were tasked with solving a puzzle in groups of two. Our results indicate that the additional contextual information provided by PASCAL had significantly positive effects on task completion time, ease of communication, mutual understanding, and co-presence. As a result, our insights contribute to the repertoire of successful interaction techniques to mediate between loosely- and tightly-coupled work in collaborative virtual environments.

Immersive knowledge spaces like museums or cultural sites are often explored by traversing pre-defined paths that are curated to unfold a specific educational narrative. To support this type of guided exploration in VR, we present a semi-automated, hands-free path traversal technique based on teleportation that features a slow-paced interaction workflow targeted at fostering knowledge acquisition and maintaining spatial awareness. In an empirical user study with 34 participants, we evaluated two variations of our technique, differing in the presence or absence of intermediate teleportation points between the main points of interest along the route. While visiting additional intermediate points was objectively less efficient, our results indicate significant benefits of this approach regarding the user’s spatial awareness and perception of interface dependability. However, the user’s perception of flow, presence, attractiveness, perspicuity, and stimulation did not differ significantly. The overall positive reception of our approach encourages further research into semi-automated locomotion based on teleportation and provides initial insights into the design space of successful techniques in this domain.

Virtual travel in Virtual Reality experiences is common, offering users the ability to explore expansive virtual spaces. Various interfaces exist for virtual travel, with speed playing a crucial role in user experience and spatial awareness. Teleportation-based interfaces provide instantaneous transitions, whereas continuous and semi-continuous methods vary in speed and control. Prior research by Bowman et al. highlighted the impact of travel speed on spatial awareness demonstrating that instantaneous travel can lead to user disorientation. However, additional cues, such as visual target selection, can aid in reorientation. This study replicates and extends Bowman’s experiment, investigating the influence of travel speed and visual target cues on spatial orientation.

Object selection in virtual environments is one of the most common and recurring interaction tasks. Therefore, the used technique can critically influence a system's overall efficiency and usability. IntenSelect is a scoring-based selection-by-volume technique that was shown to offer improved selection performance over conventional raycasting in virtual reality. This initial method, however, is most pronounced for small spherical objects that converge to a point-like appearance only, is challenging to parameterize, and has inherent limitations in terms of flexibility. We present an enhanced version of IntenSelect called IntenSelect+ designed to overcome multiple shortcomings of the original IntenSelect approach. In an empirical within-subjects user study with 42 participants, we compared IntenSelect+ to IntenSelect and conventional raycasting on various complex object configurations motivated by prior work. In addition to replicating the previously shown benefits of IntenSelect over raycasting, our results demonstrate significant advantages of IntenSelect+ over IntenSelect regarding selection performance, task load, and user experience. We, therefore, conclude that IntenSelect+ is a promising enhancement of the original approach that enables faster, more precise, and more comfortable object selection in immersive virtual environments.

The ability of a user to adjust their own scale while traveling through virtual environments enables them to inspect tiny features being ant-sized and to gain an overview of the surroundings as a giant. While prior work has almost exclusively focused on steering-based interfaces for multi-scale travel, we present three novel teleportation-based techniques that avoid continuous motion flow to reduce the risk of cybersickness. Our approaches build on the extension of known teleportation workflows and suggest specifying scale adjustments either simultaneously with, as a connected second step after, or separately from the user's new horizontal position. The results of a two-part user study with 30 participants indicate that the simultaneous and connected specification paradigms are both suitable candidates for effective and comfortable multi-scale teleportation with nuanced individual benefits. Scale specification as a separate mode, on the other hand, was considered less beneficial. We compare our findings to prior research and publish the executable of our user study to facilitate replication and further analyses.

Traditional digital tools for exploring historical data mostly rely on conventional 2D visualizations, which often cannot reveal all relevant interrelationships between historical fragments (e.g., persons or events). In this paper, we present a novel interactive exploration tool for historical data in VR, which represents fragments as spheres in a 3D environment and arranges them around the user based on their temporal, geo, categorical and semantic similarity. Quantitative and qualitative results from a user study with 29 participants revealed that most participants considered the virtual space and the abstract fragment representation well-suited to explore historical data and to discover complex interrelationships. These results were particularly underlined by high usability scores in terms of attractiveness, stimulation, and novelty, while researching historical facts with our system did not impose unexpectedly high task loads. Additionally, the insights from our post-study interviews provided valuable suggestions for future developments to further expand the possibilities of our system.

The iterative design process of virtual environments commonly generates a history of revisions that each represent the state of the scene at a different point in time. Browsing through these discrete time points by common temporal navigation interfaces like time sliders, however, can be inaccurate and lead to an uncomfortably high number of visual changes in a short time. In this paper, we therefore present a novel technique called TENETvr (Temporal Exploration and Navigation in virtual Environments via Teleportation) that allows for efficient teleportation-based travel to time points in which a particular object of interest changed. Unlike previous systems, we suggest that changes affecting other objects in the same time span should also be mediated before the teleport to improve predictability. We therefore propose visualizations for nine different types of additions, property changes, and deletions. In a formal user study with 20 participants, we confirmed that this addition leads to significantly more efficient change detection, lower task loads, and higher usability ratings, therefore reducing temporal disorientation.

The ability to reproduce previously published research findings is an important cornerstone of the scientific knowledge acquisition process. However, the exact details required to reproduce empirical experiments vary depending on the discipline. In this paper, we summarize key replication challenges as well as their specific consequences for VR locomotion research. We then present the results of a literature review on artificial locomotion techniques, in which we analyzed 61 papers published in the last five years with respect to their report of essential details required for reproduction. Our results indicate several issues in terms of the description of the experimental setup, the scientific rigor of the research process, and the generalizability of results, which altogether points towards a potential replication crisis in VR locomotion research. As a countermeasure, we provide guidelines to assist researchers with reporting future artificial locomotion experiments in a reproducible form.

Most prior teleportation techniques in virtual reality are bound to target positions in the vicinity of selectable scene objects. In this paper, we present three adaptations of the classic teleportation metaphor that enable the user to travel to mid-air targets as well. Inspired by related work on the combination of teleports with virtual rotations, our three techniques differ in the extent to which elevation changes are integrated into the conventional target selection process. Elevation can be specified either simultaneously, as a connected second step, or separately from horizontal movements. A user study with 30 participants indicated a trade-off between the simultaneous method leading to the highest accuracy and the two-step method inducing the lowest task load as well as receiving the highest usability ratings. The separate method was least suitable on its own but could serve as a complement to one of the other approaches. Based on these findings and previous research, we define initial design guidelines for mid-air navigation techniques.

In virtual navigation, maneuvering around an object of interest is a common task which requires simultaneous changes in both rotation and translation. In this paper, we present Anchored Jumping, a teleportation technique for maneuvering that allows the explicit specification of a new viewing direction by selecting a point of interest as part of the target specification process. A first preliminary study showed that naïve Anchored Jumping can be improved by an automatic counter rotation that preserves the user’s relative orientation towards their point of interest. In our second, qualitative study, this extended technique was compared with two common approaches to specifying virtual rotations. Our results indicate that Anchored Jumping allows precise and comfortable maneuvering and is compatible with techniques that primarily support virtual exploration and search tasks. Equipped with a combination of such complementary techniques, seated users generally preferred virtual over physical rotations for indoor navigation.

Group navigation can be an invaluable tool for performing guided tours in distributed virtual environments. Related work suggests that group navigation techniques should be comprehensible for both the guide and the attendees, assist the group in avoiding collisions with obstacles, and allow the creation of meaningful spatial arrangements with respect to objects of interest. To meet these requirements, we developed a group navigation technique based on short-distance teleportation (jumping) and evaluated its usability, comprehensibility, and scalability in an initial user study. After navigating with groups of up to 10 users through a virtual museum, participants indicated that our technique is easy to learn for guides, comprehensible also for attendees, non-nauseating for both roles, and therefore well-suited for performing guided tours.

We present a novel collaborative virtual reality system that offers multiple immersive 3D views at large 3D scenes. The physical setup consists of two synchronized multi-user 3D displays: a tabletop and a large vertical projection screen. These displays afford different presentations of the shared 3D scene. The wall display lends itself to the egocentric exploration at 1:1 scale, while the tabletop affords an allocentric overview. Additionally, handheld 3D portals facilitate the personal exploration of the scene, the comparison of views, and the exchange with others. Our developments enable seamless 3D interaction across these independent 3D views. This requires the simultaneous representation of user input in the different viewing contexts. However, the resulting interactions cannot be executed independently. The application must coordinate the interactions and resolve potential ambiguities to provide plausible effects. We analyze and document the challenges of seamless 3D interaction across multiple independent viewing windows, propose a high-level software design to realize the necessary functionality, and apply the design to a set of interaction tools. Our setup was tested in a formal user study, which revealed general advantages of collaborative 3D data exploration with multiple views in terms of user preference, comfort, and task performance.

We analyzed the design space of group navigation tasks in distributed virtual environments and present a framework consisting of techniques to form groups, distribute responsibilities, navigate together, and eventually split up again. To improve joint navigation, our work focused on an extension of the Multi-Ray Jumping technique that allows adjusting the spatial formation of two distributed users as part of the target specification process. The results of a quantitative user study showed that these adjustments lead to significant improvements in joint two-user travel, which is evidenced by more efficient travel sequences and lower task loads imposed on the navigator and the passenger. In a qualitative expert review involving all four stages of group navigation, we confirmed the effective and efficient use of our technique in a more realistic use-case scenario and concluded that remote collaboration benefits from fluent transitions between individual and group navigation.

We present the collaborative Virtual Reality Neurorobotics Lab, which allows multiple collocated and remote users to experience, discuss and participate in neurorobotic experiments in immersive virtual reality. We describe the coupling of the Neurorobotics Platform of the Human Brain Project with our collaborative virtual reality and 3D telepresence infrastructure and highlight future opportunities arising from our work for research on direct human interaction with simulated robots and brains.

The collaborative exploration of virtual environments benefits from joint group navigation capabilities. In this paper, we focus on the design and evaluation of a short-range teleportation technique (jumping) for a group of collocated users wearing head-mounted displays. In a pilot study with expert users, we tested three naïve group jumping approaches and derived the requirements for comprehensible group jumping. We propose a novel Multi-Ray Jumping technique to meet these requirements and report results of two formal user studies, one exploring the effects of passive jumping on simulator sickness symptoms (N=20) and a second one investigating the advantages of our novel technique compared to naïve group jumping (N=22). The results indicate that Multi-Ray Jumping decreases spatial confusion for passengers, increases planning accuracy for navigators, and reduces cognitive load for both.

Many recent head-mounted display applications and games implement a range-restricted variant of teleportation for exploring virtual environments. This travel metaphor referred to as jumping only allows to teleport to locations in the currently visible part of the scene. In this paper, we present a formal description and classification scheme for teleportation techniques and its application to the classification of jumping. Furthermore, we present the results of a user study (N=24) that compared jumping to the more conventional steering with respect to spatial updating and simulator sickness. Our results show that despite significantly faster travel times during jumping, a majority of participants (75%) achieved similar spatial updating accuracies in both conditions (mean difference 0.02°, =5.05°. In addition, jumping induced significantly less simulator sickness, which altogether justifies it as an alternative to steering for the exploration of immersive virtual environments. However, application developers should be aware that spatial updating during jumping may be impaired for individuals.

We present ShakeCast, a system for automatic peer-to-peer exchange of contact information between two persons who just shook hands. The accelerometer in a smartwatch is used to detect the physical handshake and implicitly triggers a setup-free information transfer between the users' personal smartphones using Bluetooth LE broadcasts. An abstract representation of the handshake motion data is used to disambiguate between multiple simultaneous transmissions and to prevent accidental data leakage.