@phdthesis{Moehring,
  author    = {Moehring, Mathias},
  title     = {Realistic Interaction with Virtual Objects within Arm's Reach},
  doi       = {10.25643/bauhaus-universitaet.1859},
  url       = {http://nbn-resolving.de/urn:nbn:de:gbv:wim2-20130301-18592},
  school      = {Bauhaus-Universit{\"a}t Weimar},
  pages     = {124},
  abstract  = {The automotive industry requires realistic virtual reality applications more than other domains to increase the efficiency of product development. Currently, the visual quality of virtual invironments resembles reality, but interaction within these environments is usually far from what is known in everyday life. Several realistic research approaches exist, however they are still not all-encompassing enough to be usable in industrial processes. This thesis realizes lifelike direct multi-hand and multi-finger interaction with arbitrary objects, and proposes algorithmic and technical improvements that also approach lifelike usability. In addition, the thesis proposes methods to measure the effectiveness and usability of such interaction techniques as well as discusses different types of grasping feedback that support the user during interaction. Realistic and reliable interaction is reached through the combination of robust grasping heuristics and plausible pseudophysical object reactions. The easy-to-compute grasping rules use the objects' surface normals, and mimic human grasping behavior. The novel concept of Normal Proxies increases grasping stability and diminishes challenges induced by adverse normals. The intricate act of picking-up thin and tiny objects remains challenging for some users. These cases are further supported by the consideration of finger pinches, which are measured with a specialized finger tracking device. With regard to typical object constraints, realistic object motion is geometrically calculated as a plausible reaction on user input. The resulting direct finger-based interaction technique enables realistic and intuitive manipulation of arbitrary objects. The thesis proposes two methods that prove and compare effectiveness and usability. An expert review indicates that experienced users quickly familiarize themselves with the technique. A quantitative and qualitative user study shows that direct finger-based interaction is preferred over indirect interaction in the context of functional car assessments. While controller-based interaction is more robust, the direct finger-based interaction provides greater realism, and becomes nearly as reliable when the pinch-sensitive mechanism is used. At present, the haptic channel is not used in industrial virtual reality applications. That is why it can be used for grasping feedback which improves the users' understanding of the grasping situation. This thesis realizes a novel pressure-based tactile feedback at the fingertips. As an alternative, vibro-tactile feedback at the same location is realized as well as visual feedback by the coloring of grasp-involved finger segments. The feedback approaches are also compared within the user study, which reveals that grasping feedback is a requirement to judge grasp status and that tactile feedback improves interaction independent of the used display system. The considerably stronger vibrational tactile feedback can quickly become annoying during interaction. The interaction improvements and hardware enhancements make it possible to interact with virtual objects in a realistic and reliable manner. By addressing realism and reliability, this thesis paves the way for the virtual evaluation of human-object interaction, which is necessary for a broader application of virtual environments in the automotive industry and other domains.},
  subject      = {Virtuelle Realit{\"a}t},
  language  = {en}
}
@phdthesis{Schollmeyer,
  author    = {Schollmeyer, Andre},
  title     = {Efficient and High-Quality Rendering of Higher-Order Geometric Data Representations},
  doi       = {10.25643/bauhaus-universitaet.3823},
  url       = {http://nbn-resolving.de/urn:nbn:de:gbv:wim2-20181120-38234},
  school      = {Bauhaus-Universit{\"a}t Weimar},
  pages     = {143},
  abstract  = {Computer-Aided Design (CAD) bezeichnet den Entwurf industrieller Produkte mit Hilfe von virtuellen 3D Modellen. Ein CAD-Modell besteht aus parametrischen Kurven und Fl{\"a}chen, in den meisten F{\"a}llen non-uniform rational B-Splines (NURBS). Diese mathematische Beschreibung wird ebenfalls zur Analyse, Optimierung und Pr{\"a}sentation des Modells verwendet. In jeder dieser Entwicklungsphasen wird eine unterschiedliche visuelle Darstellung ben{\"o}tigt, um den entsprechenden Nutzern ein geeignetes Feedback zu geben. Designer bevorzugen beispielsweise illustrative oder realistische Darstellungen, Ingenieure ben{\"o}tigen eine verst{\"a}ndliche Visualisierung der Simulationsergebnisse, w{\"a}hrend eine immersive 3D Darstellung bei einer Benutzbarkeitsanalyse oder der Designauswahl hilfreich sein kann. Die interaktive Darstellung von NURBS-Modellen und -Simulationsdaten ist jedoch aufgrund des hohen Rechenaufwandes und der eingeschr{\"a}nkten Hardwareunterst{\"u}tzung eine große Herausforderung. Diese Arbeit stellt vier neuartige Verfahren vor, welche sich mit der interaktiven Darstellung von NURBS-Modellen und Simulationensdaten befassen. Die vorgestellten Algorithmen nutzen neue F{\"a}higkeiten aktueller Grafikkarten aus, um den Stand der Technik bez{\"u}glich Qualit{\"a}t, Effizienz und Darstellungsgeschwindigkeit zu verbessern. Zwei dieser Verfahren befassen sich mit der direkten Darstellung der parametrischen Beschreibung ohne Approximationen oder zeitaufw{\"a}ndige Vorberechnungen. Die dabei vorgestellten Datenstrukturen und Algorithmen erm{\"o}glichen die effiziente Unterteilung, Klassifizierung, Tessellierung und Darstellung getrimmter NURBS-Fl{\"a}chen und einen interaktiven Ray-Casting-Algorithmus f{\"u}r die Isofl{\"a}chenvisualisierung von NURBSbasierten isogeometrischen Analysen. Die weiteren zwei Verfahren beschreiben zum einen das vielseitige Konzept der programmierbaren Transparenz f{\"u}r illustrative und verst{\"a}ndliche Visualisierungen tiefenkomplexer CAD-Modelle und zum anderen eine neue hybride Methode zur Reprojektion halbtransparenter und undurchsichtiger Bildinformation f{\"u}r die Beschleunigung der Erzeugung von stereoskopischen Bildpaaren. Die beiden letztgenannten Ans{\"a}tze basieren auf rasterisierter Geometrie und sind somit ebenfalls f{\"u}r normale Dreiecksmodelle anwendbar, wodurch die Arbeiten auch einen wichtigen Beitrag in den Bereichen der Computergrafik und der virtuellen Realit{\"a}t darstellen. Die Auswertung der Arbeit wurde mit großen, realen NURBS-Datens{\"a}tzen durchgef{\"u}hrt. Die Resultate zeigen, dass die direkte Darstellung auf Grundlage der parametrischen Beschreibung mit interaktiven Bildwiederholraten und in subpixelgenauer Qualit{\"a}t m{\"o}glich ist. Die Einf{\"u}hrung programmierbarer Transparenz erm{\"o}glicht zudem die Umsetzung kollaborativer 3D Interaktionstechniken f{\"u}r die Exploration der Modelle in virtuellenUmgebungen sowie illustrative und verst{\"a}ndliche Visualisierungen tiefenkomplexer CAD-Modelle. Die Erzeugung stereoskopischer Bildpaare f{\"u}r die interaktive Visualisierung auf 3D Displays konnte beschleunigt werden. Diese messbare Verbesserung wurde zudem im Rahmen einer Nutzerstudie als wahrnehmbar und vorteilhaft befunden.},
  subject      = {Rendering},
  language  = {en}
}
@phdthesis{Beck,
  author    = {Beck, Stephan},
  title     = {Immersive Telepresence Systems and Technologies},
  doi       = {10.25643/bauhaus-universitaet.3856},
  url       = {http://nbn-resolving.de/urn:nbn:de:gbv:wim2-20190218-38569},
  school      = {Bauhaus-Universit{\"a}t Weimar},
  pages     = {149},
  abstract  = {Modern immersive telepresence systems enable people at different locations to meet in virtual environments using realistic three-dimensional representations of their bodies. For the realization of such a three-dimensional version of a video conferencing system, each user is continuously recorded in 3D. These 3D recordings are exchanged over the network between remote sites. At each site, the remote recordings of the users, referred to as 3D video avatars, are seamlessly integrated into a shared virtual scenery and displayed in stereoscopic 3D for each user from his or her perspective. This thesis reports on algorithmic and technical contributions to modern immersive telepresence systems and presents the design, implementation and evaluation of the first immersive group-to-group telepresence system in which each user is represented as realistic life-size 3D video avatar. The system enabled two remote user groups to meet and collaborate in a consistent shared virtual environment. The system relied on novel methods for the precise calibration and registration of color- and depth- sensors (RGBD) into the coordinate system of the application as well as an advanced distributed processing pipeline that reconstructs realistic 3D video avatars in real-time. During the course of this thesis, the calibration of 3D capturing systems was greatly improved. While the first development focused on precisely calibrating individual RGBD-sensors, the second stage presents a new method for calibrating and registering multiple color and depth sensors at a very high precision throughout a large 3D capturing volume. This method was further refined by a novel automatic optimization process that significantly speeds up the manual operation and yields similarly high accuracy. A core benefit of the new calibration method is its high runtime efficiency by directly mapping from raw depth sensor measurements into an application coordinate system and to the coordinates of its associated color sensor. As a result, the calibration method is an efficient solution in terms of precision and applicability in virtual reality and immersive telepresence applications. In addition to the core contributions, the results of two case studies which address 3D reconstruction and data streaming lead to the final conclusion of this thesis and to directions of future work in the rapidly advancing field of immersive telepresence research.},
  subject      = {Virtuelle Realit{\"a}t},
  language  = {en}
}
@phdthesis{Weissker,
  author    = {Weißker, Tim},
  title     = {Group Navigation in Multi-User Virtual Reality},
  doi       = {10.25643/bauhaus-universitaet.4530},
  url       = {http://nbn-resolving.de/urn:nbn:de:gbv:wim2-20211124-45305},
  school      = {Bauhaus-Universit{\"a}t Weimar},
  pages     = {148},
  abstract  = {Multi-user virtual reality systems enable collocated as well as distributed users to perform collaborative activities in immersive virtual environments. A common activity in this context is to move from one location to the next as a group to explore the environment together. The simplest solution to realize these multi-user navigation processes is to provide each participant with a technique for individual navigation. However, this approach entails some potentially undesirable consequences such as the execution of a similar navigation sequence by each participant, a regular need for coordination within the group, and, related to this, the risk of losing each other during the navigation process. To overcome these issues, this thesis performs research on group navigation techniques that move group members together through a virtual environment. The presented work was guided by four overarching research questions that address the quality requirements for group navigation techniques, the differences between collocated and distributed settings, the scalability of group navigation, and the suitability of individual and group navigation for various scenarios. This thesis approaches these questions by introducing a general conceptual framework as well as the specification of central requirements for the design of group navigation techniques. The design, implementation, and evaluation of corresponding group navigation techniques demonstrate the applicability of the proposed framework. As a first step, this thesis presents ideas for the extension of the short-range teleportation metaphor, also termed jumping, for multiple users. It derives general quality requirements for the comprehensibility of the group jumping process and introduces a corresponding technique for two collocated users. The results of two user studies indicate that sickness symptoms are not affected by user roles during group jumping and confirm improved planning accuracy for the navigator, increased spatial awareness for the passenger, and reduced cognitive load for both user roles. Next, this thesis explores the design space of group navigation techniques in distributed virtual environments. It presents a conceptual framework to systematize the design decisions for group navigation techniques based on Tuckman's model of small-group development and introduces the idea of virtual formation adjustments as part of the navigation process. A quantitative user study demonstrates that the corresponding extension of Multi-Ray Jumping for distributed dyads leads to more efficient travel sequences and reduced workload. The results of a qualitative expert review confirm these findings and provide further insights regarding the complementarity of individual and group navigation in distributed virtual environments. Then, this thesis investigates the navigation of larger groups of distributed users in the context of guided museum tours and establishes three central requirements for (scalable) group navigation techniques. These should foster the awareness of ongoing navigation activities as well as facilitate the predictability of their consequences for all group members (Comprehensibility), assist the group with avoiding collisions in the virtual environment (Obstacle Avoidance), and support placing the group in a meaningful spatial formation for the joint observation and discussion of objects (View Optimization). The work suggests a new technique to address these requirements and reports on its evaluation in an initial usability study with groups of five to ten (partially simulated) users. The results indicate easy learnability for navigators and high comprehensibility for passengers. Moreover, they also provide valuable insights for the development of group navigation techniques for even larger groups. Finally, this thesis embeds the previous contributions in a comprehensive literature overview and emphasizes the need to study larger, more heterogeneous, and more diverse group compositions including the related social factors that affect group dynamics. In summary, the four major research contributions of this thesis are as follows: - the framing of group navigation as a specific instance of Tuckman's model of small-group development - the derivation of central requirements for effective group navigation techniques beyond common quality factors known from single-user navigation - the introduction of virtual formation adjustments during group navigation and their integration into concrete group navigation techniques - evidence that appropriate pre-travel information and virtual formation adjustments lead to more efficient travel sequences for groups and lower workloads for both navigators and passengers Overall, the research of this thesis confirms that group navigation techniques are a valuable addition to the portfolio of interaction techniques in multi-user virtual reality systems. The conceptual framework, the derived quality requirements, and the development of novel group navigation techniques provide effective guidance for application developers and inform future research in this area.},
  subject      = {Virtuelle Realit{\"a}t},
  language  = {en}
}
@phdthesis{Kunert,
  author    = {Kunert, Andr{\´e}},
  title     = {3D Interaction Techniques in Multi-User Virtual Reality : towards scalable templates and implementation patterns for cooperative interfaces},
  doi       = {10.25643/bauhaus-universitaet.4296},
  url       = {http://nbn-resolving.de/urn:nbn:de:gbv:wim2-20201204-42962},
  school      = {Bauhaus-Universit{\"a}t Weimar},
  pages     = {147},
  abstract  = {Multi-user projection systems provide a coherent 3D interaction space for multiple co-located users that facilitates mutual awareness, full-body interaction, and the coordination of activities. The users perceive the shared scene from their respective viewpoints and can directly interact with the 3D content. This thesis reports on novel interaction patterns for collaborative 3D interaction for local and distributed user groups based on such multi-user projection environments. A particular focus of our developments lies in the provision of multiple independent interaction territories in our workspaces and their tight integration into collaborative workflows. The motivation for such multi-focus workspaces is grounded in research on social cooperation patterns, specifically in the requirement for supporting phases of loose and tight collaboration and the emergence of dedicated orking territories for private usage and public exchange. We realized independent interaction territories in the form of handheld virtual viewing windows and multiple co-located hardware displays in a joint workspace. They provide independent views of a shared virtual environment and serve as access points for the exploration and manipulation of the 3D content. Their tight integration into our workspace supports fluent transitions between individual work and joint user engagement. The different affordances of various displays in an exemplary workspace consisting of a large 3D wall, a 3D tabletop, and handheld virtual viewing windows, promote different usage scenarios, for instance for views from an egocentric perspective, miniature scene representations, close-up views, or storage and transfer areas. This work shows that this versatile workspace can make the cooperation of multiple people in joint tasks more effective, e.g. by parallelizing activities, distributing subtasks, and providing mutual support. In order to create, manage, and share virtual viewing windows, this thesis presents the interaction technique of Photoportals, a tangible interface based on the metaphor of digital photography. They serve as configurable viewing territories and enable the individual examination of scene details as well as the immediate sharing of the prepared views. Photoportals are specifically designed to complement other interface facets and provide extended functionality for scene navigation, object manipulation, and for the creation of temporal recordings of activities in the virtual scene. A further objective of this work is the realization of a coherent interaction space for direct 3D input across the independent interaction territories in multi-display setups. This requires the simultaneous consideration of user input in several potential interaction windows as well as configurable disambiguation schemes for the implicit selection of distinct interaction contexts. We generalized the required implementation structures into a high-level software pattern and demonstrated its versatility by means of various multi-context 3D interaction tools. Additionally, this work tackles specific problems related to group navigation in multiuser projection systems. Joint navigation of a collocated group of users can lead to unintentional collisions when passing narrow scene sections. In this context, we suggest various solutions that prevent individual collisions during group navigation and discuss their effect on the perceived integrity of the travel group and the 3D scene. For collaboration scenarios involving distributed user groups, we furthermore explored different configurations for joint and individual travel. Last but not least, this thesis provides detailed information and implementation templates for the realization of the proposed interaction techniques and collaborative workspaces in scenegraph-based VR systems. These contributions to the abstraction of specific interaction patterns, such as group navigation and multi-window interaction, facilitate their reuse in other virtual reality systems and their adaptation to further collaborative scenarios.},
  subject      = {Virtuelle Realit{\"a}t},
  language  = {en}
}