@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{Blickling2006,
  author    = {Blickling, Arno},
  title     = {Spezifikation des Bau-Solls durch interaktive Modellierung auf virtuellen Baustellen},
  doi       = {10.25643/bauhaus-universitaet.790},
  url       = {http://nbn-resolving.de/urn:nbn:de:gbv:wim2-20061105-8311},
  school      = {Bauhaus-Universit{\"a}t Weimar},
  year      = {2006},
  abstract  = {Heutige Methoden zur Soll-Spezifikation von Bauleistungen (Kostenermittlung und zeitliche Ablaufplanung) gehen von einer abstrahierten und vereinfachten Betrachtung der Zusammenh{\"a}nge bei Bauprojekten aus. Leistungsverzeichnisse, Kostenermittlungen und Bauzeitpl{\"a}ne orientieren sich nur indirekt an der Geometrie des Bauwerks und der Baustelle. Die dabei verwendeten Medien wie Papier, 2D-Dateien, digitale Leistungsbeschreibungen oder 3D-Darstellungen lassen die Suche nach Informationen auf der Baustelle zu einem zeitaufw{\"a}ndigen und in Anbetracht existierender Medientechnologien ineffizienten Prozess werden. Interaktive virtuelle Umgebungen erlauben die Aufl{\"o}sung starrer Zusammenh{\"a}nge durch interaktive Eingriffe des Anwenders und visualisieren komplexe bauproduktionstechnische Vorg{\"a}nge. Das Konzept der visuellen interaktiven Simulation der Bauproduktion sieht vor, die Soll-Spezifikation anhand eines interaktiven 3D-Modells zu entwickeln, um r{\"a}umliche Ver{\"a}nderungen und parallele Prozesse auf der virtuellen Baustelle im Rahmen der Entscheidungsfindung zum Bauablauf besser ber{\"u}cksichtigen zu k{\"o}nnen. Verlangt man einen hohen Grad an Interaktivit{\"a}t mit dem 3D-Modell, dann bieten sich Computerspieltechnologien sehr gut zu Verifikationszwecken an. Die visuelle interaktive Simulation der Bauproduktion ist damit als eine 3D-modellbasierte Methode der Prozessmodellierung zu verstehen, die Entscheidungen als Input ben{\"o}tigt und die Kostenermittlung sowie die zeitliche Ablaufplanung als Output liefert.},
  subject      = {Virtuelle Realit{\"a}t},
  language  = {de}
}
@phdthesis{Jakob2004,
  author    = {Jakob, Patrick},
  title     = {Die Bedeutung von klassischen Elementen in virtueller Architektur - Untersucht am Beispiel der Wand},
  doi       = {10.25643/bauhaus-universitaet.651},
  url       = {http://nbn-resolving.de/urn:nbn:de:gbv:wim2-20050708-6849},
  school      = {Bauhaus-Universit{\"a}t Weimar},
  year      = {2004},
  abstract  = {Die Dissertation exploriert und evaluiert die Definition einer Entsprechung der architektonischen Kategorie der Wand f{\"u}r virtuelle Architekturen. Es wird der Frage nachgegangen, inwieweit eine architektonische Strukturierung in der virtuellen Architektur fortzuf{\"u}hren ist, um Handlungs- und Kommunikationsstrukturen zu sichern. Der erste Teil motiviert die Arbeit und vermittelt die Grundlagen und Termini, die in einem direkten Zusammenhang mit der virtuellen Architektur verwendet werden. Der folgende Teil konzentriert sich ausschließlich auf die reale Architektur. Ausgehend vom Element der Wand wird, in einer analytischen und architekturtheoretischen Betrachtung, ein Modell von Raumkategorien entwickelt, welches im Hinblick auf die virtuelle Architektur von besonderer Bedeutung ist. Die aus der Analyse gewonnen Erkenntnisse in Form von Raumkategorien werden im dritten Teil aus der realen in die virtuelle Architektur {\"u}bertragen. Das folgende Kapitel beschreibt drei Experimente, die Fra-gen, Hypothesen und Ans{\"a}tze aus den vorangegangenen Kapiteln empirisch evaluieren. Im abschließenden Kapitel werden die Erkenntnisse der experimentellen Untersuchung im Kontext des architektonischen Gestaltens von virtuellen Architekturen diskutiert.},
  subject      = {Virtuelle Realit{\"a}t},
  language  = {de}
}
@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}
}
@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{Regenbrecht2000,
  author    = {Regenbrecht, Holger},
  title     = {Faktoren f{\"u}r Pr{\"a}senz in virtueller Architektur},
  doi       = {10.25643/bauhaus-universitaet.33},
  url       = {http://nbn-resolving.de/urn:nbn:de:gbv:wim2-20040216-359},
  school      = {Bauhaus-Universit{\"a}t Weimar},
  year      = {2000},
  abstract  = {Die Dissertation adressiert das Gebiet der Entwicklung von (r{\"a}umlicher) Pr{\"a}senz in computer-generierten virtuellen Umgebungen im speziellen und virtueller Architektur im besonderen. Der erste Teil motiviert die Arbeit, f{\"u}hrt in die Terminologie ein und beschreibt die grundlegenden Prinzipien der virtuellen Realit{\"a}t (VR) und von VR-basierter Architektur. Der Schwerpunkt liegt auf sogenannten immersiven VR-Systemen. Der folgende Teil erarbeitet den theoretischen Hintergrund der Entwickling von Pr{\"a}senz unter besonderer Beachtung philosophischer und kognitiver Ans{\"a}tze. Ein eigenes Kapitel widmet sich der Klassifikation von Pr{\"a}senz-Faktoren unter dem Gesichtspunkt der praktischen Gestaltung virtueller Architektur. Letztendlich werden verschiedene empirische Untersuchungen vorgestellt, die die entwickelten Ansaetze evaluieren und beschreiben. Die Ergebnisse werden im Kontext des architektonischen Gestaltens diskutiert.},
  subject      = {Architektur},
  language  = {de}
}
@phdthesis{Salzmann2010,
  author    = {Salzmann, Holger},
  title     = {Collaboration in Co-located Automotive Applications},
  doi       = {10.25643/bauhaus-universitaet.1422},
  url       = {http://nbn-resolving.de/urn:nbn:de:gbv:wim2-20100712-15102},
  school      = {Bauhaus-Universit{\"a}t Weimar},
  year      = {2010},
  abstract  = {Virtual reality systems offer substantial potential in supporting decision processes based purely on computer-based representations and simulations. The automotive industry is a prime application domain for such technology, since almost all product parts are available as three-dimensional models. The consideration of ergonomic aspects during assembly tasks, the evaluation of humanmachine interfaces in the car interior, design decision meetings as well as customer presentations serve as but a few examples, wherein the benefit of virtual reality technology is obvious. All these tasks require the involvement of a group of people with different expertises. However, current stereoscopic display systems only provide correct 3D-images for a single user, while other users see a more or less distorted virtual model. This is a major reason why these systems still face limited acceptance in the automotive industry. They need to be operated by experts, who have an advanced understanding of the particular interaction techniques and are aware of the limitations and shortcomings of virtual reality technology. The central idea of this thesis is to investigate the utility of stereoscopic multi-user systems for various stages of the car development process. Such systems provide multiple users with individual and perspectively correct stereoscopic images, which are key features and serve as the premise for the appropriate support of collaborative group processes. The focus of the research is on questions related to various aspects of collaboration in multi-viewer systems such as verbal communication, deictic reference, embodiments and collaborative interaction techniques. The results of this endeavor provide scientific evidence that multi-viewer systems improve the usability of VR-applications for various automotive scenarios, wherein co-located group discussions are necessary. The thesis identifies and discusses the requirements for these scenarios as well as the limitations of applying multi-viewer technology in this context. A particularly important gesture in real-world group discussions is referencing an object by pointing with the hand and the accuracy which can be expected in VR is made evident. A novel two-user seating buck is introduced for the evaluation of ergonomics in a car interior and the requirements on avatar representations for users sitting in a car are identified. Collaborative assembly tasks require high precision. The novel concept of a two-user prop significantly increases the quality of such a simulation in a virtual environment and allows ergonomists to study the strain on workers during an assembly sequence. These findings contribute toward an increased acceptance of VR-technology for collaborative development meetings in the automotive industry and other domains.},
  subject      = {Virtuelle Realit{\"a}t},
  language  = {en}
}
@phdthesis{Springer2008,
  author    = {Springer, Jan P.},
  title     = {Multi-Frame Rate Rendering},
  doi       = {10.25643/bauhaus-universitaet.1371},
  url       = {http://nbn-resolving.de/urn:nbn:de:gbv:wim2-20081127-14395},
  school      = {Bauhaus-Universit{\"a}t Weimar},
  year      = {2008},
  abstract  = {Multi-frame rate rendering is a parallel rendering technique that renders interactive parts of a 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, by optical superposition or digital composition, and displayed. The results of a user study confirm that multi-frame rate rendering can significantly improve the interaction performance. Multi-frame rate rendering is naturally implemented on a graphics cluster. With the recent availability of multiple graphics cards in standalone systems the method can also be implemented on a single computer system where memory bandwidth is much higher compared to off-the-shelf networking technology. This decreases overall latency and further improves interactivity. Multi-frame rate rendering was also investigated on a single graphics processor by interleaving the rendering streams for the interactive elements and the rest of the scene. This approach enables the use of multi-frame rate rendering on low-end graphics systems such as laptops, mobile phones, and PDAs. Advanced multi-frame rate rendering techniques reduce the limitations of the basic approach. The interactive manipulation of light sources and their parameters affects the entire scene. A multi-GPU deferred shading method is presented that splits the rendering task into a rasterization and lighting pass and assigns the passes to the appropriate image generators such that light manipulations at high frame rates become possible. A parallel volume rendering technique allows the manipulation of objects inside a translucent volume at high frame rates. This approach is useful for example in medical applications, where small probes need to be positioned inside a computed-tomography image. Due to the asynchronous nature of multi-frame rate rendering artifacts may occur during migration of objects from the slow to the fast graphics card, and vice versa. Proper state management allows to almost completely avoid these artifacts. Multi-frame rate rendering significantly improves the interactive manipulation of objects and lighting effects. This leads to a considerable increase of the size for 3D scenes that can be manipulated compared to conventional methods.},
  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{Willenbacher2000,
  author    = {Willenbacher, Susanne},
  title     = {Untersuchungen zu r{\"a}umlichen Benutzerschnittstellen am Beispiel der Pr{\"a}sentation von Stadtinformationen},
  doi       = {10.25643/bauhaus-universitaet.34},
  url       = {http://nbn-resolving.de/urn:nbn:de:gbv:wim2-20040218-363},
  school      = {Bauhaus-Universit{\"a}t Weimar},
  year      = {2000},
  abstract  = {Schwerpunkt der Arbeit ist die Auseinandersetzung mit den M{\"o}glichkeiten und Grenzen der Desktop-VR als neue Generation der Benutzerschnittstellen. Besondere Bedeutung bei dieser Art des Interface-Designs kommt den Metaphern zu. Ein großer Teil der Arbeit besch{\"a}ftigt sich mit der Klassifikation, der Auswahl und dem Einsatz passender Metaphern unter Ber{\"u}cksichtigung der in der Applikation darzustellenden Informationsinhalte. Aus der Kombination dieser beiden Merkmale (Art der Metapher, Informationsinhalt) ergeben sich vier verschiedene virtuelle Umgebungen, deren Eigenschaften und Besonderheiten konkretisiert und an Beispielen aus dem Anwendungsgebiet der Stadtinformationssysteme vorgestellt werden. Als praktischer Untersuchungsgegenstand dient das Anwendungsgebiet der Stadtinformationssysteme. Die theoretisch basierten Erkenntnisse und Schlußfolgerungen werden durch statistische Untersuchungen, in Form von Frageb{\"o}gen zu Stadtinformationssystemen, {\"u}berpr{\"u}ft und konkretisiert.},
  subject      = {Virtuelle Realit{\"a}t},
  language  = {de}
}