World-in-Miniatures (WIMs) are an established technique in virtual reality (VR) that provide an overview of the surrounding virtual environment. While traditionally used to support navigation over larger distances and distant manipulation in large-scale spaces, their potential for comparing alternative versions of a virtual environment has not been exploited. In this paper, we introduce a Multi-WIM paradigm that facilitates the detailed exploration and comparison of urban planning alternatives. Each alternative is visualized in a separate WIM. The WIMs can be arranged side by side (juxtaposed) or stacked. Stacking allows toggling between alternatives or using a swipe tool where on each side one alternative is shown. These three modes (juxtaposed, toggle, swipe) provide flexible ways of exploring differences and similarities between alternatives, with highlighting functionalities that reveal differences of functional units across designs. We evaluated the Multi-WIM paradigm in a single-factor VR user study (N=24), combining a single-user experiment with a multi-user exploration. Participants had to identify differences and estimate distances, areas and heights across urban planning alternatives. Results show that the stacked toggle mode was significantly faster for finding differences while the juxtaposed view better supported a landmark recall task. Furthermore, toggle was the overall preferred technique in the single-user mode. In contrast, in multi-user settings participants favored juxtaposed, as it fostered collaborative discussion and shared sensemaking. The identified design trade-offs between efficiency and collaboration indicate the need to incorporate all three WIM modes, together with seamless transitions among them, in urban planning applications so as to accommodate both loosely and tightly coupled phases of collaboration.

Engaging in rhythmic synchronized activities such as dancing or coordinated exercises is a powerful driver of social connection, as interpersonal entrainment promotes feelings of closeness, empathy, and cooperation. However, in media-based settings such as Social Virtual Reality (SVR), maintaining synchrony is technically challenging. Even modest latency can disrupt the temporal coordination needed for shared rhythm, thereby diminishing social presence, user engagement and the quality of interaction. Our work explores whether synchrony-reinforcing feedback can mitigate latency effects in a dyadic VR rowing task. Participants received real-time visual, audio, or audio-visual feedback: visual feedback was provided through particle effects, and audio feedback through music, both of which intensified with stronger synchronization and diminished as it weakened. Latency was systematically varied. Our findings show that latency, especially higher delays, significantly disrupts coordination and a sense of togetherness. Participants often misattribute these disruptions to personal or interpersonal factors. Audio-visual feedback reduces these effects, supporting smoother interaction and masking symptoms of latency. The task load remains stable across latency levels, but decreases when clear, multimodal feedback is provided. Notably, while closeness remains robust, togetherness deteriorates in the absence of timely, multimodal cues. Our results suggest that latency effects can be partially addressed through perceptual design. Providing multimodal feedback is a key strategy for maintaining synchrony, reducing cognitive effort, and sustaining meaningful social interaction in latency-prone environments.

We present the first dataset, an annotation scheme, discourse analysis, and baseline experiments on argumentation and domain content types in scholarly articles on political science, specifically on the theory of International Relations (IR). The dataset comprises over 1 600 sentences stemming from three foundational articles on Neo-Realism, Liberalism, and Constructivism. We show that our annotation scheme enables educationally-relevant insight into the scholarly IR discourse and that state-of-the-art classifiers, while effective in distinguishing basic argumentative elements (Claims and Support/Attack relations) reaching up to 0.97 micro F1 , require domain-specific training and fine-tuning on the more fine-grained tasks of relation and content type prediction.

Shared synchronised activities, such as dancing and singing, can promote social bonding in both physical and virtual settings, but are susceptible to network latencies in mediated environments, such as social virtual reality (VR). Temporal delays can hinder interpersonal entrainment, causing users to feel out of sync, and reduce presence. While prior work has examined how stimulus type and frequency affect synchrony perception, the role of rhythmic interaction, central to many interactive synchronised experiences, remains unexplored. We conducted a within-subject study with 32 participants to systematically investigate how rhythmic interaction shapes synchrony perception of rhythmic audiovisual stimuli in networked VR environments. Motor behaviour and subjective synchrony ratings ($\mathrm{n}=32$) are analysed, complemented by eye-tracking metrics from a quality-controlled subset ($\mathrm{n}=25$). Through controlled stimulus onset asynchronies (SOAs) between audio and video stimuli, we simulate network latency scenarios wshere (1) audio precedes video (as in VR dance environments where music playback is synchronised to a global clock while remote dancer movements appear delayed), and (2) video precedes audio (as in orchestra experiences where a conductor's movements are perceived first, followed by a delayed auditory response from the orchestra). Participants either synchronised hand movements with a virtual avatar or passively observed it across two stimulus frequencies (0.5 Hz and 1 Hz), for both audio- and video-leading offsets. Our results show that rhythmic interaction significantly increases tolerance to audiovisual offsets, shifting the left decision criterion (LDC) by up to 66 ms, the point of subjective synchrony (PSS) by up to 31 ms, and widening the window of subjective synchrony (WSS) by up to 59 ms. These effects suggest that rhythmic interaction can reduce sensitivity to asynchronies in audio-leading scenarios, such as VR dance environments. We also found that temporal offsets influence rhythmic interaction behaviour and confirm that recent findings on the influence of stimulus frequency on PSS and temporal offsets on pupil dilation can to a certain extent be replicated in interactive VR.

Making virtual reality (VR) more accessible for novice and nondigital users has largely focused on single-user solutions, such as tutorials, tooltips, and visual guidance cues. While structured onboarding protocols have proven effective, they do not scale well for multiple collocated users due to varying assistance needs, different learning speeds, and guidance preferences. Additionally, the sudden isolation upon entering VR can cause disorientation, particularly in group settings where users may lose awareness of their physical and social surrounding. This paper proposes a novel onboarding framework that extends traditional procedures with four phases: 1) entering video see-through mixed reality after putting on the HMD, 2) interactive tutorials in mixed reality, 3) adaptive group transition strategies into VR, and 4) structured exit mechanisms. In our implementation of the framework, we explore three concepts for group transitions: individual, sequential, and collective. In a user study with 36 participants, we collected feedback on our mixedreality onboarding approach and evaluate the usability, co-presence, agency, and continuity of our three proposed transition techniques and compare it to the common direct transition into virtual reality. Our results indicate a clear preference for onboarding through an additional mixed reality stage and provide valuable insights into advantages and trade-offs of the different group transition strategies.

We present ICS-MR, a dataset containing three conversational scenarios designed for the evaluation of communication quality in Mixed Reality (MR) systems. Along with detailed descriptions of the conversation tasks, we provide all the materials required to incorporate the tasks into MR user studies. The materials also support application of the scenarios in real-world and video-conferencing contexts for studies that, for example, call for comparison of immersive systems against reference communication media. Open-source Unity implementations of the scenarios are also made available, supporting direct usage of the scenarios in distributed, multi-user experiments. The conversation tasks have all been administered in recent scientific works that address the evaluation of user experiences in immersive communication systems, allowing analysis and comparison of each scenario's evoked behavioral properties. The ICS-MR dataset therefore contributes valuable resources for further research on communication in immersive systems.

Group-to-group telepresence systems immerse geographically separated groups in a shared interaction space where remote users are represented as avatars. Notably, such systems allow users to interact with collocated and remote interlocutors simultaneously. In this context, where virtual user representations can be directly compared with real users, we investigate how visual realism (avatar type) and aural realism (presence of spatial audio) affect communication. Furthermore, we examine how communication differs between collocated and remote pairs of interlocutors. In our user study, groups of four participants perform a collaborative conversation task under the aforementioned visual and aural realism conditions. Our results indicate that avatar realism has positive effects on subjective ratings of perceived message understanding and group cohesion, and yields behavioural differences that indicate more interactivity and engagement. Few significant effects of aural realism were observed. Comparisons between collocated and remote communication found that collocated communication was perceived as more effective, but that more visual attention was paid to both remote participants than the collocated user.

Virtual pointing rays are a commonly employed interaction metaphor allowing users of mixed reality applications to select out-of-reach virtual objects. However, fast hand movements can cause the visual representation of the ray to move quickly across the visual field, leading to motion artefacts that cause multiple copies of the ray to appear in discrete locations. In this work, we conduct a user study to investigate whether the conditions for motion artefact occurrence arise during a selection task that participants undertake with a pointing ray. We analyse the recorded gaze and ray movement data from the study to show that pointing actions create the conditions necessary for motion artefacts to appear. In addition, we propose a motion blur effect that we apply to the pointing ray with the aim of mitigating motion artefacts. The blur effect is evaluated in the aforementioned user study and is found to improve the perceived smoothness of ray selection, without affecting selection performance.

In collocated social virtual reality, the relative physical and virtual positions of users are often synchronised to reduce audio-visual inconsistencies and the risk of collisions between users. For virtual navigation previous work has proposed group navigation techniques that maintain spatial synchronisation. This, however, limits user autonomy and can be particularly frustrating when some users would prefer to remain at their current virtual position, as can be the case when users have differing goals, interests, or tasks within the virtual environment. In this paper, we introduce a two-phase confirmation-based group navigation concept for collocated scenarios which allows users to stay behind and catch up to the group based on individual confirmation. The confirmation to catch up can be triggered by the group’s guide, the individual user or both. Ghost avatars, which visualise the physical locations of other users, are used to avoid physical collisions in situations where part of the group has already virtually navigated to a new location. We evaluate the three confirmation-based techniques in a user study (N = 24) in the context of a guided tour in a virtual museum and compare it to a baseline group navigation technique. Our findings show that users prefer having the autonomy to decide when to follow their group. Despite increased complexity, the proposed techniques achieved comparable levels of co-presence, spatial orientation, and understanding of others’ positions in both the virtual and physical environments as the baseline, effectively balancing user autonomy, navigation understanding and social experience.

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.

The lack of visually guided data exploration tools limits the scope of research questions communication scientists are able to study. The Comment Analyzer steps in where traditional statistical tools fail when it comes to researching the commenting behavior of news article readers. The basis of such an analysis are comment-thread corpora in which comments are tagged with various deliberative quality indicators as well as political stance. Our analysis tool provides a visual querying system for the exploration and analysis of such corpora and allows social scientists to gain insights into the distributions and relations between comment attributes, the homogeneity of thread sets, frequent thread structures and changes in comment qualities over the course of a single but in particular of multiple threads at once. We developed the tool in close collaboration with communication scientists in a user-centered approach. The system has proven its utility in thorough reviews with the communication scientists, by corroborating existing findings in the literature but particularly by provoking and answering new research questions. Final reviews with five independent experts confirmed these observations and revealed the potential of the Comment Analyzer for other datasets currently being created and analyzed in the communication sciences.

Conversational agents in virtual environments are an established approach for immersively conveying the information and narratives of museums and cultural heritage while expanding their accessibility to a wider and remote audience. The rapid development of large language models and text-to-speech technologies has raised the agents’ conversational level significantly, which allows their use for proactive guidance of visitors. This raises the vital question of how such agents should be visually represented to promote Knowledge transfer in immersive virtual environments. In this paper, we compared two representation concepts for agent embodiments in the context of a virtual museum by examining a stylized humanoid guide and a novel animism-based approach that enables users to talk to exhibited objects. Our work addresses the challenge of naturally introducing a virtual educational environment to users and encouraging their interest and engagement with the content. A user study $(N=29)$ revealed high usability and similar presence scores for the experience with each of the embodiments. A majority of participants showed a preference for the animated objects. In terms of user experience, they evoked significant stimulation and high levels of engagement. Our results suggest that agents that show emotions through appropriate word choice influence engagement levels. Based on our findings, we recommend humanoid guides for delivering general background information, while animated objects promote detailed questions about their own stories and a more stimulating exchange.

Virtual Reality (VR) enables users to meet, converse, and collaborate in shared virtual environments. For such communication systems, many system factors can affect user experience and perception. To effectively allocate system resources, understanding of the relative influence of such factors is required. One important factor is a spatial auralization, which has been shown to elevate users’ experience in traditional and single-user VR systems. However, its effect in multi-party social VR has not been fully investigated. In this work, we conducted a study assessing the effect of spatial audio on audiovisual plausibility and presence perception in a three-user interactive communication scenario. Triads of participants perform a collaborative conversation task under three conditions: a VR condition with binaural spatial audio, a VR condition with simple diotic audio, and a real-world reference condition. This paper presents the results of the study based on questionnaire-based evaluation.

Spatial audio representations have been shown to positively impact user experience in traditional, non-immersive communication media. While spatial audio also contributes to presence in single-user immersive VR, its impact in virtual communication scenarios has not yet been fully understood. This work aims to further investigate which communication scenarios benefit from spatial audio representations. We present a study in which pairs of interlocutors undertake a collaborative task in an audiovisual Virtual Environment (VE) under different auralization and scene arrangement conditions. The novel task is designed to encourage simultaneous conversation and movement, with the aim of increasing the relevance of spatial hearing. Results are obtained through questionnaires measuring social presence and plausibility, as well as through conversational and behavioral analysis. Although participants are shown to favor binaural auralization over diotic audio in a direct active-listening comparison, no significant differences in social presence, plausibility, or communication behavior could be found. Our results suggest that spatial audio may not affect user experience in dyadic communication scenarios where spatial auditory information is not directly relevant to the considered task.

Standing in a large crowd can be uncomfortable and usually results in other users obstructing the view of the virtual environment. In this paper, we present four techniques designed to improve the user’s view in crowded environments. Inspired by related work on various transparency and clipping techniques, as well as observed user behavior in crowded scenarios, our paper addresses the visibility problem by locally manipulating the appearance of other users. Three of our techniques define a region of interest using a handheld flashlight metaphor. Depending on the technique, occluding users are either pushed to the side, scaled, or made partially transparent. The fourth technique allows users to vertically adjust their position. A user study with 24 participants found that the transparency technique was advantageous for quick search tasks. However, in a realistic museum setting, no clear favorite could be determined because the techniques make different trade-offs and users weighted these aspects differently. In a final ranking, the vertical position adjustment and transparency techniques were the most popular, but the scaling technique and vertical position adjustment were found to be the most natural.

Immersive recordings capture virtual reality interactions and are used in various contexts such as education and entertainment. However, there has been only limited research on requirements and techniques for editing such recordings. We interviewed expert editors of video recordings to understand their workflows, familiarised them with immersive recordings, and asked them about what editing challenges and capabilities they can envision for immersive recordings. The experts identified several functionalities they considered relevant for editing, including viewer placement, control over the viewer’s size, support for live and asynchronous collaboration, and different transition types.

Embodied conversational agents are an established approach for immersively conveying the narratives and information of virtual museums. Recent advances in large language models and text-to-speech systems enable the active guidance of users by agents and raise the question of how such assistants should be visually embodied to engage visitors and promote knowledge transfer. This demo showcases a stylized humanoid guide, a novel animism-based approach with speaking objects, and a combination of both concepts to interactively guide users through a digital replica of the famous Gropius Room at the Bauhaus University in Weimar.

Virtual Reality (VR) has become an important tool for conducting behavioral studies in realistic, reproducible environments. In this paper, we present ISA, an Immersive Study Analyzer system designed for the comprehensive analysis of social VR studies. For in-depth analysis of participant behavior, ISA records all user actions, speech, and the contextual environment of social VR studies. A key feature is the ability to review and analyze such immersive recordings collaboratively in VR, through support of behavioral coding and user-defined analysis queries for efficient identification of complex behavior. Respatialization of the recorded audio streams enables analysts to follow study participants' conversations in a natural and intuitive way. To support phases of close and loosely coupled collaboration, ISA allows joint and individual temporal navigation, and provides tools to facilitate collaboration among users at different temporal positions. An expert review confirms that ISA effectively supports collaborative immersive analysis, providing a novel and effective tool for nuanced understanding of user behavior in social VR studies.

This paper presents a proof-of-concept study conducted to analyze the effect of simple diotic vs. spatial, position-dynamic binaural synthesis on social presence in VR, in comparison with face-to-face communication in the real world, for a sample two-party scenario. A conversational task with shared visual reference was realized. The collected data includes questionnaires for direct assessment, tracking data, and audio and video recordings of the individual participants’ sessions for indirect evaluation. While tendencies for improvements with binaural over diotic presentation can be observed, no significant difference in social presence was found for the considered scenario. The gestural analysis revealed that participants used the same amount and type of gestures in face-to-face as in VR, highlighting the importance of non-verbal behavior in communication. As part of the research, an end-to-end framework for conducting communication studies and analysis has been developed.

RGBD cameras can capture users and their actions in the real world for reconstruction of photo-realistic volumetric avatars that allow rich interaction between spatially distributed telepresence parties in virtual environments. In this paper, we present and evaluate a system design that enables volumetric avatar reconstruction at increased frame rates. We demonstrate that we can overcome the limited capturing frame rate of commodity RGBD cameras such as the Azure Kinect by dividing a set of cameras into two spatio-temporally offset reconstruction groups and implementing a real-time reconstruction pipeline to fuse the temporally offset RGBD image streams. Comparisons of our proposed system against capture configurations possible with the same number of RGBD cameras indicate that it is beneficial to use a combination of spatially and temporally offset RGBD cameras, allowing increased reconstruction frame rates and scene coverage while producing temporally consistent volumetric avatars.

The combination of smartphone Augmented Reality (AR) and Virtual Reality (VR) makes it possible for on-site and remote users to simultaneously explore a physical space and its digital twin through an asymmetric Collaborative Virtual Environment (CVE). In this paper, we investigate two spatial awareness visualizations to enable joint exploration of a space for dyads consisting of a smartphone AR user and a head-mounted display VR user. Our study revealed that both, a mini-map-based method and an egocentric compass method with a path visualization, enabled the on-site visitors to locate and follow a virtual companion reliably and quickly. Furthermore, the embodiment of the AR user by an inverse kinematics avatar allowed the use of natural gestures such as pointing and waving which was preferred over text messages by the participants of our study. In an expert review in a museum and its digital twin we observed an overall high social presence for on-site AR and remote VR visitors and found that the visualizations and the avatar embodiment successfully facilitated their communication and collaboration.

Abstract This paper presents new techniques for seamlessly transitioning between parallel coordinate plots, star plots, and scatter plots. The star plot serves as a mediator visualization between parallel coordinate plots and scatter plots since it uses lines to represent data items as parallel coordinates do and can arrange axes orthogonally as used for scatter plots. The design of the transitions also motivated a new variant of the star plot, the polycurve star plot, that uses curved lines instead of straight ones and has advantages both in terms of space utilization and the detection of clusters. Furthermore, we developed a geometrically motivated method to embed scatter points from a scatter plot into star plots and parallel coordinate plots to track the transition of structural information such as clusters and correlations between the different plot types. The integration of our techniques into an interactive analysis tool for exploring multivariate data demonstrates the advantages and utility of our approach over a multi‐view approach for scatter plots and parallel coordinate plots, which we confirmed in a user study and concrete usage scenarios.

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.

Abstract In this paper we propose a novel and efficient rasterization‐based approach for direct rendering of isosurfaces. Our method exploits the capabilities of task and mesh shader pipelines to identify subvolumes containing potentially visible isosurface geometry, and to efficiently extract primitives which are consumed on the fly by the rasterizer. As a result, our approach requires little preprocessing and negligible additional memory. Direct isosurface rasterization is competitive in terms of rendering performance when compared with ray‐marching‐based approaches, and significantly outperforms them for increasing resolution in most situations. Since our approach is entirely rasterization based, it affords straightforward integration into existing rendering pipelines, while allowing the use of modern graphics hardware features, such as multi‐view stereo for efficient rendering of stereoscopic image pairs for geometry‐bound applications. Direct isosurface rasterization is suitable for applications where isosurface geometry is highly variable, such as interactive analysis scenarios for static and dynamic data sets that require frequent isovalue adjustment.

In this article, we propose a system design and implementation for output-sensitive reconstruction, transmission and rendering of 3D video avatars in distributed virtual environments. In our immersive telepresence system, users are captured by multiple RGBD sensors connected to a server that performs geometry reconstruction based on viewing feedback from remote telepresence parties. This feedback and reconstruction loop enables visibility-aware level-of-detail reconstruction of video avatars regarding geometry and texture data, and considers individual and groups of collocated users. Our evaluation reveals that our approach leads to a significant reduction of reconstruction times, network bandwidth requirements and round-trip times as well as rendering costs in many situations.

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.

This paper presents a visual analytics system for exploring, analyzing and comparing argument structures in essay corpora. We provide an overview of the corpus by a list of ArguLines which represent the argument units of each essay by a sequence of glyphs. Each glyph encodes the stance, the depth and the relative position of an argument unit. The overview can be ordered in various ways to reveal patterns and outliers. Subsets of essays can be selected and analyzed in detail using the Argument Unit Occurrence Tree which aggregates the argument structures using hierarchical histograms. This hierarchical view facilitates the estimation of statistics and trends concerning the progression of the argumentation in the essays. It also provides insights into the commonalities and differences between selected subsets. The text view is the necessary textual basis to verify conclusions from the other views and the annotation process. Linking the views and interaction techniques for visual filtering, studying the evolution of stance within a subset of essays and scrutinizing the order of argumentative units enable a deep analysis of essay corpora. Our expert reviews confirmed the utility of the system and revealed detailed and previously unknown information about the argumentation in our sample corpus.

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.

Image-based 3D reconstructions and their visualization in virtual reality promise novel opportunities to explore and analyze 3D reconstructions of real objects, buildings and places. However, the faithfulness of the presented data is not always obvious and, in most cases, a 3D reconstruction cannot be compared directly to its corresponding real world instance. However, in case of reconstruction methods based on structure from motion (SFM), a large number of raw photos is available. This motivated us to develop a novel interaction technique for the visual comparison of details of 3D models with projections of the corresponding image sections, e.g. in order to rapidly verify the authenticity of perceived features. The results of a formal user study (n=18) demonstrate the general usability of such visual provenance information as well as benefits of the comparison in vicinity of the features in question over a separate image gallery. Further observations informed our iterative design process and led to the development of an improved interactive visualization. Our final implementation provides a spatial and content-related overview while retaining the efficiency of the original approach.

Abstract This paper presents a short‐contact multitouch vocabulary for interacting with scatterplot matrices (SPLOMs) on wall‐sized displays. Fling‐based gestures overcome central interaction challenges of such large displays by avoiding long swipes on the typically blunt surfaces, frequent physical navigation by walking for accessing screen areas beyond arm's reach in the horizontal direction and uncomfortable postures for accessing screen areas in the vertical direction. Furthermore, we make use of the display's high resolution and large size by supporting the efficient specification of two‐tiered focus + context regions which are consistently propagated across the SPLOM. These techniques are complemented by axis‐centered and lasso‐based selection techniques for specifying subsets of the data. An expert review as well as a user study confirmed the potential and general usability of our seamlessly integrated multitouch interaction techniques for SPLOMs on large vertical displays.

This paper presents a multitouch vocabulary for interacting with parallel coordinates plots on wall-sized displays. The gesture set relies on principles such as two-finger range definition, a functional distinction of background and foreground for applying the Hold-and-Move concept to wall-sized displays as well as fling-based interaction for triggering and controlling long-range movements. Our implementation demonstrates that out-of-reach problems and limitations regarding multitouch technology and display size can be tackled by the coherent integration of our multitouch gestures. Expert reviews indicate that our gesture vocabulary helps to solve typical analysis tasks that require interaction beyond arms' reach, and it also shows how often certain gestures were used.

Fitts's law facilitates approximate comparisons of target acquisition performance across a variety of settings. Conceptually, also the index of difficulty of 3D object manipulation with six degrees of freedom can be computed, which allows the comparison of results from different studies. Prior experiments, however, often revealed much worse performance than one would reasonably expect on this basis. We argue that this discrepancy stems from confounding variables and show how Fitts's law and related research methods can be applied to isolate and identify relevant factors of motor performance in 3D manipulation tasks. The results of a formal user study ( n=21) demonstrate competitive performance in compliance with Fitts's model and provide empirical evidence that simultaneous 3D rotation and translation can be beneficial.

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.

This paper presents a visualization framework that aids readers in understanding and analyzing the contents of medium-sized text collections that are typical for the opus of a single or few authors. We contribute several document-based visualization techniques to facilitate the exploration of the work of the German author Bazon Brock by depicting various aspects of its texts, such as the TextGenetics that shows the structure of the collection along with its chronology. The ConceptCircuit augments the TextGenetics with entities - persons and locations that were crucial to his work. All visualizations are sensitive to a wildcard-based phrase search that allows complex requests towards the author's work. Further development, as well as expert reviews and discussions with the author Bazon Brock, focused on the assessment and comparison of visualizations based on automatic topic extraction against ones that are based on expert knowledge.

In Computer-Aided Design (CAD), Non-Uniform Rational B-Splines (NURBS) are a common model representation for export, simulation and visualization. In this paper, we present a direct rendering method for trimmed NURBS models based on their parametric description. Our approach builds on a novel trimming method and a three-pass pipeline which both allow for a sub-pixel precise visualization. The rendering pipeline bypasses tessellation limitations of current hardware using a feedback mechanism. In contrast to existing work, our trimming method scales well with a large number of trim curves and estimates the trimmed surface's footprint in screen-space which allows for an anti-aliasing with minimal performance overhead. Fragments with trimmed edges are routed into a designated off-screen buffer for subsequent blending with background faces. The evaluation of the presented algorithms shows that our rendering system can handle CAD models with ten thousands of trimmed NURBS surfaces. The suggested two-level data structure used for trimming outperforms state-of-the-art methods while being more precise and memory efficient. Our curve coverage estimation used for anti-aliasing provides an efficient trade-off between quality and performance compared to multisampling or screen-space anti-aliasing approaches.

We present a comprehensive multitouch input mapping for 3D navigation of multiscale 3D models. In contrast to prior work, our technique offers explicit control over 3D rotation, 3D translation, and uniform scaling with manipulative gestures that do not require graphical widgets. Our proposed technique is consistent with the established RST mapping (rotation, scaling, translation) for 2D mul-titouch input and follows suggestions from prior work on multitouch 3D interaction. Our implementation includes a rendering technique that can reduce perceptual conflicts of 3D touch input on stereoscopic displays. We also report on two user studies that informed the suggested interaction design and confirmed its usability.

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.

The accurate calibration and registration of a set of color and depth (RGBD) sensors into a shared coordinate system is an essential requirement for 3D surround capturing systems. We present a method to calibrate multiple unsynchronized RGBD-sensors with high accuracy in a matter of minutes by sweeping a tracked checkerboard through the desired capturing space in front of each sensor. Through the sweeping process, a large number of robust correspondences between the depth and the color image as well as the 3D world positions can be automatically established. In order to obtain temporally synchronized correspondences between an RGBD-sensor's data streams and the tracked target's positions we apply an off-line optimization process based on error minimization and a coplanarity constraint. The correspondences are entered into a 3D look-up table which is used during runtime to transform depth and color information into the application's world coordinate system. Our proposed method requires a manual effort of less than one minute per RGBD-sensor and achieves a high calibration accuracy with an average 3D error below 3.5 mm and an average texture reprojection error smaller than 1 pixel.

Modern virtual reality simulations require a constant high-frame rate from the rendering engine. They may also require very low latency and stereo images. Previous rendering engines for virtual reality applications have exploited spatial and temporal coherence by using image-warping to re-use previous frames or to render a stereo pair at lower cost than running the full render pipeline twice. However these previous approaches have shown artifacts or have not scaled well with image size. We present a new image-warping algorithm that has several novel contributions: an adaptive grid generation algorithm for proxy geometry for image warping; a low-pass hole-filling algorithm to address un-occlusion; and support for transparent surfaces by efficiently ray casting transparent fragments stored in per-pixel linked lists of an A-Buffer. We evaluate our algorithm with a variety of challenging test cases. The results show that it achieves better quality image-warping than state-of-the-art techniques and that it can support transparent surfaces effectively. Finally, we show that our algorithm can achieve image warping at rates suitable for practical use in a variety of applications on modern virtual reality equipment.

Abstract We present a natural extension of two‐dimensional parallel‐coordinates plots for revealing relationships in time‐dependent multi‐attribute data by building on the idea that time can be considered as the third dimension. A time slice through the visualization represents a certain point in time and can be viewed as a regular parallel‐coordinates display. A vertical slice through one of the axes of the parallel‐coordinates display would show a time‐series plot. For a focus‐and‐context Integration of both views, we embed time‐series plots between two adjacent axes of the parallel‐coordinates plot. Both time‐series plots are drawn using a pseudo three‐dimensional perspective with a single vanishing point. An independent parallel‐coordinates panel that connects the two perspectively displayed time‐series plots can move forward and backward in time to reveal changes in the relationship between the time‐dependent attributes. The visualization of time‐series plots in the context of the parallel‐coordinates plot facilitates the exploration of time‐related aspects of the data without the need to switch to a separate display. We provide a consistent set of tools for selecting and contrasting subsets of the data, which are important for various application domains.

We present an integrated approach for the calibration and registration of color and depth (RGBD) sensors into a joint coordinate system without explicitly identifying intrinsic or extrinsic camera parameters. Our method employs a tracked checkerboard to establish a number of correspondences between positions in color and depth camera space and in world space. These correspondences are used to construct a single calibration and registration volume per RGBD sensor which directly maps raw depth sensor values into a joint coordinate system and to their associated color values. Our evaluation demonstrates an accuracy with an average 3D error below 3 mm and an average texture deviation smaller than 0.5 pixels for a space of about 1.5 m × 1.8 m × 1.5 m.

Abstract We developed a visual analysis tool to support the verification, assessment, and presentation of alleged cases of plagiarism. The analysis of a suspicious document typically results in a compilation of categorized “finding spots”. The categorization reveals the way in which the suspicious text fragment was created from the source, e.g. by obfuscation, translation, or by shake and paste. We provide a three‐level approach for exploring the finding spots in context. The overview shows the relationship of the entire suspicious document to the set of source documents. A glyph‐based view reveals the structural and textual differences and similarities of a set of finding spots and their corresponding source text fragments. For further analysis and editing of the finding spot's assessment, the actual text fragments can be embedded side‐by‐side in the diffline view. The different views are tied together by versatile navigation and selection operations. Our expert reviewers confirm that our tool provides a significant improvement over existing static visualizations for assessing plagiarism cases.

In this paper, we present a flexible and efficient approach for the integration of order-independent transparency into a deferred shading pipeline. The intermediate buffers for storing fragments to be shaded are extended with a dynamic and memory-efficient storage for transparent fragments. The transparency of an object is not fixed and remains programmable until fragment processing, which allows for the implementation of advanced materials effects, interaction techniques or adaptive fade-outs. Traversing costs for shading the transparent fragments are greatly reduced by introducing a tile-based light-culling pass. During deferred shading, opaque and transparent fragments are shaded and composited in front-to-back order using the retrieved lighting information and a physically-based shading model. In addition, we discuss various configurations of the system and further enhancements. Our results show that the system performs at interactive frame rates even for complex scenarios.

We present a system for visualizing food ingredients with a glyph-based approach aimed at children between the ages of four and eight, approximately. The intention is to visually explain and to visually argue that a certain food a child is eager to eat is healthy or, more often, is not healthy. Therefore, we introduced two comic-like characters whose shape and features depend on the main ingredients of food products. These characters can be directly displayed on a parent's smartphone by scanning the barcode of a food product. Our study showed that children are able to recognize several ingredient manifestations encoded as visual attributes and thus to consider a food product as being healthy or not.

Photoportals build on digital photography as a unifying metaphor for reference-based interaction in 3D virtual environments. Virtual photos and videos serve as threedimensional references to objects, places, moments in time and activities of users. Our Photoportals also provide access to intermediate or alternative versions of a scenario and allow the review of recorded task sequences that include life-size representations of the captured users. We propose to exploit such references to structure collaborative activities of collocated and remote users. Photoportals offer additional access points for multiple users and encourage mutual support through the preparation and provision of references for manipulation and navigation tasks. They support the pattern of territoriality with configurable space representations that can be used for private interaction, as well as be shared and exchanged with others.

Our vision is that regardless of future variations in the interior of airplane cabins, we can utilize ever-advancing state-of-the-art virtual and mixed reality technologies with the latest research in neuroscience and psychology to achieve high levels of comfort for passengers. Current surveys on passenger's experience during air travel reveal that they are least satisfied with the amount and effectiveness of their personal space, and their ability to work, sleep or rest. Moreover, considering current trends it is likely that the amount of available space is likely to decrease and therefore the passenger's physical comfort during a flight is likely to worsen significantly. Therefore, the main challenge is to enable the passengers to maintain a high level of comfort and satisfaction while being placed in a restricted physical space.

In NURBS-based isogeometric analysis, the basis functions of a 3D model's geometric description also form the basis for the solution space of variational formulations of partial differential equations. In order to visualize the results of a NURBS-based isogeometric analysis, we developed a novel GPU-based multi-pass isosurface visualization technique which performs directly on an equivalent rational Bézier representation without the need for discretization or approximation. Our approach utilizes rasterization to generate a list of intervals along the ray that each potentially contain boundary or isosurface intersections. Depth-sorting this list for each ray allows us to proceed in front-to-back order and enables early ray termination. We detect multiple intersections of a ray with the higher-order surface of the model using a sampling-based root-isolation method. The model's surfaces and the isosurfaces always appear smooth, independent of the zoom level due to our pixel-precise processing scheme. Our adaptive sampling strategy minimizes costs for point evaluations and intersection computations. The implementation shows that the proposed approach interactively visualizes volume meshes containing hundreds of thousands of Bézier elements on current graphics hardware. A comparison to a GPU-based ray casting implementation using spatial data structures indicates that our approach generally performs significantly faster while being more accurate.

We present a novel immersive telepresence system that allows distributed groups of users to meet in a shared virtual 3D world. Our approach is based on two coupled projection-based multi-user setups, each providing multiple users with perspectively correct stereoscopic images. At each site the users and their local interaction space are continuously captured using a cluster of registered depth and color cameras. The captured 3D information is transferred to the respective other location, where the remote participants are virtually reconstructed. We explore the use of these virtual user representations in various interaction scenarios in which local and remote users are face-to-face, side-by-side or decoupled. Initial experiments with distributed user groups indicate the mutual understanding of pointing and tracing gestures independent of whether they were performed by local or remote participants. Our users were excited about the new possibilities of jointly exploring a virtual city, where they relied on a world-in-miniature metaphor for mutual awareness of their respective locations.

We present the Product Explorer, an interactive parallel coordinates display for facilitating the selection process of typical products offered in online shops. Users can quickly narrow down the product search to a small subset or even a single product by using our visual query interface. Our study confirms that our interactive Product Explorer is a fast and easy-to-use tool for the product selection process of casual users.

We present the two-finger gesture hold-and-move as an alternative to the disruptive long-tap which utilizes dwell times for switching from panning to object dragging mode in touch interfaces. We make use of a second finger for object selection and manipulation while workspace panning is operated with the first finger. Since both operations can be performed simultaneously, the cumbersome and hard-to-control autoscrolling function is no longer needed when dragging an object beyond the currently visible viewport. Single-finger panning and pinch zooming still work as expected. A user study revealed that hold-and-move enables faster object dragging than the conventional dwell-time approach and that it is preferred by most users.

The WORDGRAPH helps writers in visually choosing phrases while writing a text. It checks for the commonness of phrases and allows for the retrieval of alternatives by means of wildcard queries. To support such queries, we implement a scalable retrieval engine, which returns high-quality results within milliseconds using a probabilistic retrieval strategy. The results are displayed as WORDGRAPH visualization or as a textual list. The graphical interface provides an effective means for interactive exploration of search results using filter techniques, query expansion, and navigation. Our observations indicate that, of three investigated retrieval tasks, the textual interface is sufficient for the phrase verification task, wherein both interfaces support context-sensitive word choice, and the WORDGRAPH best supports the exploration of a phrase's context or the underlying corpus. Our user study confirms these observations and shows that WORDGRAPH is generally the preferred interface over the textual result list for queries containing multiple wildcards.

NETSPEAK helps writers in choosing words while writing a text. It checks for the commonness of phrases and allows for the retrieval of alternatives by means of wildcard queries. To support such queries, we implement a scalable retrieval engine, which returns high-quality results within milliseconds using a probabilistic retrieval strategy. The results are displayed as WORDGRAPH visualization or as a textual list. The graphical interface provides an effective means for interactive exploration of search results using filter techniques, query expansion and navigation. Our observations indicate that, of three investigated retrieval tasks, the textual interface is sufficient for the phrase verification task, wherein both views support context-sensitive word choice, and the WORDGRAPH best supports the exploration of a phrase's context or the underlying corpus. The preferred view for context-sensitive word choice seems to depend on query complexity (i.e. the number of wildcards in a query).

We developed a new hand model for increasing the robustness of finger-based manipulations of virtual objects. Each phalanx of our hand model consists of a number of deformable soft bodies, which dynamically adapt to the shape of grasped objects based on the applied forces. Stronger forces directly result in larger contact areas, which increase the friction between hand and object as would occur in reality. For a robust collision-based soft body simulation, we extended the lattice-shape matching algorithm to work with adaptive stiffness values, which are dynamically derived from force and velocity thresholds. Our implementation demonstrates that this approach allows very precise and robust grasping, manipulation and releasing of virtual objects and performs in real-time for a variety of complex scenarios. Additionally, laborious tuning of object and friction parameters is not necessary for the wide range of objects that we typically grasp with our hands.

We present a study that compares finger-based direct interaction to controller-based ray interaction in a CAVE as well as in head-mounted displays. We focus on interaction tasks within reach of the users' arms and hands and explore various feedback methods including visual, pressure-based tactile and vibro-tactile feedback. Furthermore, we enhanced a precise finger tracking device with a direct pinch-detection mechanism to improve the robustness of grasp detection. Our results indicate that finger-based interaction is generally preferred if the functionality and ergonomics of manually manipulated virtual artifacts has to be assessed. However, controller-based interaction is often faster and more robust. In projection-based environments finger-based interaction almost reaches the task completion times and the subjective robustness of controller-based interaction if the grasping heuristics relies on our direct pinch detection. It also improves significantly by adding tactile feedback, while visual feedback proves sufficient in head-mounted displays. Our findings provide a guideline for the design of fine grain finger-based interfaces.

Stereoscopic multi-user systems provide multiple users with individual views of a virtual environment. We developed a new projection-based stereoscopic display for six users, which employs six customized DLP projectors for fast time-sequential image display in combination with polarization. Our intelligent high-speed shutter glasses can be programmed from the application to adapt to the situation. For instance, it does this by staying open if users do not look at the projection screen or switch to a VIP high brightness mode if less than six users use the system. Each user is tracked and can move freely in front of the display while perceiving perspectively correct views of the virtual environment. Navigating a group of six users through a virtual world leads to situations in which the group will not fit through spatial constrictions. Our augmented group navigation techniques ameliorate this situation by fading out obstacles or by slightly redirecting individual users along a collision-free path. While redirection goes mostly unnoticed, both techniques temporarily give up the notion of a consistent shared space. Our user study confirms that users generally prefer this trade-off over naïve approaches.

Natural Interaction in virtual environments is a key requirement for the virtual validation of functional aspects in automotive product development processes. Natural Interaction is the metaphor people encounter in reality: the direct manipulation of objects by their hands. To enable this kind of Natural Interaction, we propose a pseudophysical metaphor that is both plausible enough to provide realistic interaction and robust enough to meet the needs of industrial applications. Our analysis of the most common types of objects in typical automotive scenarios guided the development of a set of refined grasping heuristics to support robust finger-based interaction of multiple hands and users. The objects' behavior in reaction to the users' finger motions is based on pseudophysical simulations, which also take various types of constrained objects into account. In dealing with real-world scenarios, we had to introduce the concept of Normal Proxies, which extend objects with appropriate normals for improved grasp detection and grasp stability. An expert review revealed that our interaction metaphors allow for an intuitive and reliable assessment of several functionalities of objects found in a car interior. Follow-up user studies showed that overall task performance and usability are similar for CAVE and HMD environments. For larger objects and more gross manipulation, using the CAVE without employing a virtual hand representation is preferred, but for more fine-grained manipulation and smaller objects, the HMD turns out to be beneficial.

Natural Interaction in virtual environments is a key requirement for the virtual validation of functional aspects in automotive product development processes. Natural Interaction is the metaphor people encounter in reality: the direct manipulation of objects by their hands. To enable this kind of Natural Interaction, we propose a pseudo-physical metaphor that is both plausible enough to provide realistic interaction and robust enough to meet the needs of industrial applications. Our analysis of the most common types of objects in typical automotive scenarios guided the development of a set of refined grasping heuristics to support robust finger-based interaction of multiple hands and users. The objects' behavior in reaction to the users' finger motions is based on pseudo-physical simulations, which also take various types of constrained objects into account. In dealing with real-world scenarios, we had to introduce the concept of Normal Proxies, which extend objects with appropriate normals for improved grasp detection and grasp stability. An expert review revealed that our interaction metaphors allow for an intuitive and reliable assessment of several functionalities of objects found in a car interior.

Display systems typically operate at a minimum rate of 60 Hz. However, existing VR-architectures generally produce application updates at a lower rate. Consequently, the display is not updated by the application every display frame. This causes a number of undesirable perceptual artifacts. We describe an architecture that provides a programmable display layer (PDL) in order to generate updated display frames. This replaces the default display behavior of repeating application frames until an update is available. We will show three benefits of the architecture typical to VR. First, smooth motion is provided by generating intermediate display frames by per-pixel depth-image warping using 3D motion fields. Smooth motion eliminates various perceptual artifacts due to judder. Second, we implement fine-grained latency reduction at the display frame level using a synchronized prediction of simulation objects and the viewpoint. This improves the average quality and consistency of latency reduction. Third, a crosstalk reduction algorithm for consecutive display frames is implemented, which improves the quality of stereoscopic images. To evaluate the architecture, we compare image quality and latency to that of a classic level-of-detail approach.

The Globefish is a novel desktop input device for three-dimensional object manipulation and viewpoint navigation. It consists of an elastically suspended 3D trackball, which provides a natural mapping for position-controlled 3D rotations. Rate-controlled 3D translations are performed by pushing the trackball into the appropriate direction. The device is manipulated by the fingertips allowing for precise interaction with virtual objects. The Globefish was designed for 3D graphics applications such as computer aided design (CAD), digital content creation (DCC) and 3D games.

We are investigating the utility of a projection-based stereoscopic two-user system for applications in the automotive industry. In this paper we compare real-world pointing to pointing at virtual objects in a two-user scenario. In our study we investigated the following situation: One user points at an object while the second person has to guess the referenced object. Our results indicate that pointing at objects in a virtual world is much less precise than pointing in the real world even for a well calibrated stereoscopic two-user system. Pointing techniques like outlining an object or pointing from a distance produce more errors than the corresponding real-world techniques, but they are less error prone than interactions requiring to touch a virtual object. Our findings are a first step to qualify direct interaction techniques in a multi-user projection-based system.

Designing low end-to-end latency system architectures for virtual reality is still an open and challenging problem. We describe the design, implementation and evaluation of a client-server depth-image warping architecture that updates and displays the scene graph at the refresh rate of the display. Our approach works for scenes consisting of dynamic and interactive objects. The end-to-end latency is minimized as well as smooth object motion generated. However, this comes at the expense of image quality inherent to warping techniques. We evaluate the architecture and its design trade-offs by comparing latency and image quality to a conventional rendering system. Our experience with the system confirms that the approach facilitates common interaction tasks such as navigation and object manipulation.

This paper investigates the usability of tracked wands equipped with additional input sensors for system control tasks in 3D interaction scenarios. We integrated a thumb-operated circular touchpad into a hand-held wand and compared the performance of our input device to common ray-based interaction in a menu selection and parameter adjustment task. The results show that both interfaces can be highly efficient, but ray-based interaction is only competitive if large-sized graphical interface representations are provided. In contrast, touchpad input performs well independent of the size of the graphical elements due to proprioceptive and tactile feedback.

This paper presents a highly efficient direct trimming technique for NURBS surfaces, which is applicable to tessellation-based rendering as well as ray tracing systems. The central idea is to split the trim curves into monotonic segments with respect to the two parameter dimensions of the surface patches. We use an optimized bisection method to classify a point with respect to each monotonic trim curve segment without performing an actual intersection test. Our hierarchical acceleration structure allows the use of a large number of such curve segments and performs the bisection method only for points contained in the bounding boxes of the curve segments. We have integrated our novel point classification scheme into a GPU-based NURBS ray casting system and implemented the entire trimmed NURBS rendering algorithm in a single OpenGL GLSL shader. The shader can handle surfaces and trim curves of arbitrary degrees, which allows the use of original CAD data without incorporating any approximations. Performance data confirms that our trimming approach can deal with hundreds of thousands of trim curves at interactive rates. Our point classification scheme can be applied to other application domains dealing with complex curved regions including flood fills, font rendering and vector graphics mapped on arbitrary surfaces.

The automotive industry uses physical seating bucks, which are minimal mockups of a car interior, to assess various aspects of the planned interior early in the development process. In a virtual seating buck, users wear a head-mounted display (HMD) which overlays a virtual car interior on a physical seating buck. We have developed a two-user virtual seating buck system, which allows two users to take the role of the driver and co-driver respectively. Both users wear tracked head-mounted displays and see the virtual car interior from the respective view points enabling them to properly interact with the interface elements of a car. We use this system for the development, test and evaluation of novel human-machine interface concepts for future car models. We provide each user with an avatar, since the two co-located users need to see each others' actions. Our evaluation of different head and hand models for representing the two users indicate that the user representations and motions should be as realistic as possible even though the focus is on testing interface elements operated by the users' fingers. The participants of our study also expressed that they clearly prefer the two-user seating buck over a single-user system since it directly supports the face-to-face discussions of features and problems of a newly developed interface.

Access control is an important aspect of shared virtual environments. Resource access may not only depend on prior authorization, but also on context of usage such as distance or position in the scene graph hierarchy. In virtual worlds that allow user-created content, participants must be able to define and exchange access rights to control the usage of their creations. Using object capabilities, fine-grained access control can be exerted on the object level. We describe our experiences in the application of the object-capability model for access control to object-manipulation tasks common to collaborative virtual environments. We also report on a prototype implementation of an object-capability safe virtual environment that allows anonymous, dynamic exchange of access rights between users, scene elements, and autonomous actors.

Multi-frame rate rendering is a parallel rendering technique that renders interactive parts of the scene on one graphics card while the rest of the scene is rendered asynchronously on a second graphics card. The resulting color and depth images of both render processes are composited and displayed. This paper presents advanced multi-frame rate rendering techniques, which remove limitations of the original approach and reduce artifacts. The interactive manipulation of light sources and their parameters affects the entire scene. Our multi-GPU deferred shading splits the rendering task into a rasterization and lighting pass and distributes the passes to the appropriate graphics card to enable light manipulations at high frame rates independent of the geometry complexity of the scene. We also developed a parallel volume rendering technique, which allows the manipulation of objects inside a translucent volume at high frame rates. Due to the asynchronous nature of multi-frame rate rendering artifacts may occur during the migration of objects from the slow to the fast graphics card, and vice versa. We show how proper state management can be used to avoid these artifacts almost completely. These techniques were developed in the context of a single-system multi-GPU setup, which considerably simplifies the implementation and increases performance.

We describe an architecture that provides a programmable display layer in order to allow the execution of custom programs on consecutive display frames. This replaces the default display behavior of repeating application frames until an update is available. The architecture is implemented using a multi-GPU system. We will show three applications of the architecture typical to VR. First, smooth motion is provided by generating intermediate display frames by per-pixel depth-image warping using 3D motion fields. Smooth motion can be beneficial for walk-throughs of large scenes. Second, we implement fine-grained latency reduction at the display frame level using a synchronized prediction of simulation objects and the viewpoint. This improves the average quality and consistency of latency reduction. Third, a crosstalk reduction algorithm for consecutive display frames is implemented, which improves the quality of stereoscopic images.

We present a new tactile feedback system for finger-based interactions in immersive virtual reality applications that consists of shape memory alloy wires wrapped around tracked linger thimbles. The wires touch the inside of the finger tips and provide an impression when they are shortened. We use this system to communicate linger contacts with virtual objects in an application for usability and reachability studies of car interiors. Our experiments and an initial pilot study revealed that this type of feedback helps users to perform direct manipulation tasks with more reliability

Stereo displays suffer from crosstalk, an effect that reduces or even inhibits the viewer's ability to correctly perceive depth. Previous work on software crosstalk reduction focussed on the preprocessing of static scenes which are viewed from a fixed viewpoint. However, in virtual environments scenes are dynamic, and are viewed from various viewpoints in real-time on large display areas. In this paper, three methods are introduced for reducing crosstalk in virtual environments. A non-uniform crosstalk model is described, which can be used to accurately reduce crosstalk on large display areas. In addition, a novel temporal algorithm is used to address the problems that occur when reducing crosstalk in dynamic scenes. This way, high-frequency jitter caused by the erroneous assumption of static scenes can be eliminated. Finally, a perception based metric is developed that allows us to quantify crosstalk. We provide a detailed description of the methods, discuss their tradeoffs, and compare their performance with existing crosstalk reduction methods

We introduce a new concept for improved interaction with complex scenes: multi-frame rate rendering and display. Multi-frame rate rendering produces a multi-frame rate display by optically or digitally compositing the results of asynchronously running image generators. Interactive parts of a scene are rendered at the highest possible frame rates while the rest of the scene is rendered at regular frame rates. The composition of image components generated with different update rates may cause certain visual artifacts, which can be partially overcome with our rendering techniques. The results of a user study confirm that multi-frame rate rendering can significantly improve the interaction performance while slight visual artifacts are either not even recognized or gladly tolerated by users. Overall, digital composition shows the most promising results, since it introduces the least artifacts while requiring the transfer of frame buffer content between different image generators

We introduce an architecture for smooth motion in virtual environments. The system performs forward depth image warping to produce images at video refresh rates. In addition to color and depth, our 3D warping approach records per-pixel motion information during rendering of the three-dimensional scene. These enhanced depth images are used to perform per-pixel advection, which considers object motion and view changes. Our dual graphics card architecture is able to render the 3D scene at the highest possible frame rate on one graphics card, while doing the depth image warping on a second graphics engine at video refresh rate.

We present a powerful framework for 3D-texture-based rendering of multiple arbitrarily intersecting volumetric datasets. Each volume is represented by a multi-resolution octree-based structure and we use out-of-core techniques to support extremely large volumes. Users define a set of convex polyhedral volume lenses, which may be associated with one or more volumetric datasets. The volumes or the lenses can be interactively moved around while the region inside each lens is rendered using interactively defined multi-volume shaders. Our rendering pipeline splits each lens into multiple convex regions such that each region is homogenous and contains a fixed number of volumes. Each such region is further split by the brick boundaries of the associated octree representations. The resulting puzzle of lens fragments is sorted in front-to-back or back-to-front order using a combination of a view-dependent octree traversal and a GPU-based depth peeling technique. Our current implementation uses slice-based volume rendering and allows interactive roaming through multiple intersecting multi-gigabyte volumes.

We introduce two new six degree of freedom desktop input devices based on the key concept of combining forceless isotonic rotational input with force-requiring elastic translational input. The GlobeFish consists of a custom three degrees of freedom trackball which is elastically connected to a frame. The trackball is accessible from the top and bottom and can be moved slightly in all spatial directions by using force. The GlobeMouse device works in a similar way. Here the trackball is placed on top of a movable base, which requires to change the grip on the device to switch between rotating the trackball and moving the base.Our devices are manipulated with the fingertips allowing precise interaction with virtual objects. The elastic translation allows uniform input for all three axes and the isotonic trackball provides a natural mapping for rotations. Our user study revealed that the new devices perform significantly better in a docking task in comparison to the SpaceMouse, an integrated six degrees of freedom controller. Subjective data confirmed these results.

We present our experiences of combining wave field synthesis audio with a projection-based multi-viewer stereo display. Wave field synthesis is able to simulate spatial sound sources of various kinds without the need for headphones or user tracking. Multi-viewer systems support multiple tracked users with individual perspectively correct stereoscopic images. The combination of both approaches allows the consistent display of virtual objects and spatial audio sources for multiple participants. First impressions with two application scenarios confirm that sound sources can be quite well located in space by each user. The system allows the creation of sound sources attached to virtual objects, which can be moved around in real-time without perceivable latency. In addition users appreciated the possibility of natural communication while they were exploring the audio-visual scenarios.

We present the i-Disc, a tool to interactively visualize and explore medium sized topic maps. Topic maps contain two basic structures: the topic hierarchy and the associations between topics. Our system presents the topic hierarchy in a radial planar layout by encoding different hierarchy levels as separate rings. Associations are displayed on demand as three-dimensional arcs across the topic landscape. By separating these two topic map structures into different spatial dimensions, we untangle the often complex topic map graph. A perspective rendering of our layout generates a natural focus and context display. Our elementary circular design allows quick perception of the overall topic map structure while interactive navigation and exploration provide access to details on demand. The tool is implemented as a client-server application and integrates seamlessly into existing web based environments.

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This paper presents projector-based illumination techniques for creating correct occlusion effects for optical see-through setups. We project view-dependent occlusion shadows onto the real surfaces that are located behind virtual objects. This results in a perfect occlusion of real objects by virtual ones. We have implemented and tested our approach in the context of the Virtual Showcase display. We describe a hardware extension for projecting light into the showcase and present our rendering techniques for displaying occlusion shadows for single and multi-user environments as well as for single and multi-light-projector configurations. We also report on the limitations of our system for multi-user situations and describe our experiences with a first experimental prototype.

We have developed a new input device that allows users to intuitively specify three-dimensional coordinates in graphics applications. The device consists of a cube-shaped box with three perpendicular rods passing through the center and buttons on the top for additional control. The rods represent the X, Y, and Z axes of a given coordinate system. Pushing and pulling the rods specifies constrained motion along the corresponding axes. Embedded within the device is a six degree of freedom tracking sensor, which allows the rods to be continually aligned with a coordinate system located in a virtual world. We have integrated the device into two visualization prototypes for crash engineers and geologists from oil and gas companies. In these systems the Cubic Mouse controls the position and orientation of a virtual model and the rods move three orthogonal cutting or slicing planes through the model. We have evaluated the device with experts from these domains, who were enthusiastic about its ease of use.

Describes how a physical simulation can be integrated with our Responsive Workbench system to support complex assembly tasks involving multiple hands and users. Our system uses the CORIOLIS physical simulation package extended to meet the real-time requirements for our highly interactive virtual environment. We develop a new set of interface tools that exploit the natural properties of physical simulation (i.e. the superposition of forces). Our tools are based on sets of springs connecting the user's hand to a virtual object. Visualizing these springs provides "visual force feedback" of the applied forces and facilitates the prediction of the objects' behavior. Our force-based interaction concept allows multiple hands and users to manipulate a single object without the need for locking the object.

This paper describes tools and techniques for the exploration of gee-scientific data from the oil and gas domain in stereoscopic virtual environments. The two main sources of data in the exploration task are seismic volumes and multivariate well logs of physical properties down a bore hole. We have developed a props-based interaction device called the cubic mouse to allow more direct and intuitive interaction with a cubic seismic volume. This device effectively places the seismic cube in the user's hand. Geologists who have tried this device have been enthusiastic about the ease of use, and were adept only a few moments after picking it up. We have also developed a multi-modal, visualisation and sonification technique for the dense, multivariate well log data. The visualisation can show two well log variables mapped along the well geometry in a bivariate colour scheme, and another variable on a sliding lens. A sonification probe is attached to the lens so that other variables can be heard. The sonification is based on a Geiger-counter metaphor that is widely understood and which makes it easy to explain. The data is sonified at higher or lower resolutions depending on the speed of the lens. Sweeps can be made at slower rates and over smaller intervals to home in on peaks, boundaries or other features in the full resolution data set.

We have built a systemthatallows usersto naturallymanipulatevirtual 3D models with both hands on the Responsive Workbench, a tabletop VR device.Our design is largely based upon Guiard's observations of how humans distribute work between the two hands in the real world.We show how to apply these principles for the workbench environment and describe many issues encountered during the design.We first develop a framework for two-handed interaction and then explore a variety of two-handed 3D tools and interactive techniques.Related issues include how constraints are implemented and controlled by the two hands and how transitions between one-handedand two-handed tasks occur seernlessly.Informal observations of the system in practice show that users can perform navigation and manipulation tasks easily and with little training using the two-handed environment.One of our interesting findings was that users often performed two-handed manipulations by combining two otherwise independent one-handed tools in a synergistic fashion.In these cases, we did not program two-handed behaviors explicitly into the system; instead they emerged naturally.

Article The two-user Responsive Workbench: support for collaboration through individual views of a shared space Share on Authors: Maneesh Agrawala Stanford University, Stanford, CA Stanford University, Stanford, CAView Profile , Andrew C. Beers Stanford University, Stanford, CA Stanford University, Stanford, CAView Profile , Ian McDowall Fakespace, Inc., Mountain View, CA Fakespace, Inc., Mountain View, CAView Profile , Bernd Fröhlich Stanford University, Stanford, CA Stanford University, Stanford, CAView Profile , Mark Bolas Fakespace, Inc., Mountain View, CA Fakespace, Inc., Mountain View, CAView Profile , Pat Hanrahan Stanford University, Stanford, CA Stanford University, Stanford, CAView Profile Authors Info & Claims SIGGRAPH '97: Proceedings of the 24th annual conference on Computer graphics and interactive techniquesAugust 1997 Pages 327–332https://doi.org/10.1145/258734.258875Online:03 August 1997Publication History 168citation1,305DownloadsMetricsTotal Citations168Total Downloads1,305Last 12 Months58Last 6 weeks7 Get Citation AlertsNew Citation Alert added!This alert has been successfully added and will be sent to:You will be notified whenever a record that you have chosen has been cited.To manage your alert preferences, click on the button below.Manage my AlertsNew Citation Alert!Please log in to your account Save to BinderSave to BinderCreate a New BinderNameCancelCreateExport CitationPublisher SiteGet Access