TY - THES A1 - Lux, Christopher T1 - A Data-Virtualization System for Large Model Visualization N2 - Interactive scientific visualizations are widely used for the visual exploration and examination of physical data resulting from measurements or simulations. Driven by technical advancements of data acquisition and simulation technologies, especially in the geo-scientific domain, large amounts of highly detailed subsurface data are generated. The oil and gas industry is particularly pushing such developments as hydrocarbon reservoirs are increasingly difficult to discover and exploit. Suitable visualization techniques are vital for the discovery of the reservoirs as well as their development and production. However, the ever-growing scale and complexity of geo-scientific data sets result in an expanding disparity between the size of the data and the capabilities of current computer systems with regard to limited memory and computing resources. In this thesis we present a unified out-of-core data-virtualization system supporting geo-scientific data sets consisting of multiple large seismic volumes and height-field surfaces, wherein each data set may exceed the size of the graphics memory or possibly even the main memory. Current data sets fall within the range of hundreds of gigabytes up to terabytes in size. Through the mutual utilization of memory and bandwidth resources by multiple data sets, our data-management system is able to share and balance limited system resources among different data sets. We employ multi-resolution methods based on hierarchical octree and quadtree data structures to generate level-of-detail working sets of the data stored in main memory and graphics memory for rendering. The working set generation in our system is based on a common feedback mechanism with inherent support for translucent geometric and volumetric data sets. This feedback mechanism collects information about required levels of detail during the rendering process and is capable of directly resolving data visibility without the application of any costly occlusion culling approaches. A central goal of the proposed out-of-core data management system is an effective virtualization of large data sets. Through an abstraction of the level-of-detail working sets, our system allows developers to work with extremely large data sets independent of their complex internal data representations and physical memory layouts. Based on this out-of-core data virtualization infrastructure, we present distinct rendering approaches for specific visualization problems of large geo-scientific data sets. We demonstrate the application of our data virtualization system and show how multi-resolution data can be treated exactly the same way as regular data sets during the rendering process. An efficient volume ray casting system is presented for the rendering of multiple arbitrarily overlapping multi-resolution volume data sets. Binary space-partitioning volume decomposition of the bounding boxes of the cube-shaped volumes is used to identify the overlapping and non-overlapping volume regions in order to optimize the rendering process. We further propose a ray casting-based rendering system for the visualization of geological subsurface models consisting of multiple very detailed height fields. The rendering of an entire stack of height-field surfaces is accomplished in a single rendering pass using a two-level acceleration structure, which combines a minimum-maximum quadtree for empty-space skipping and sorted lists of depth intervals to restrict ray intersection searches to relevant height fields and depth ranges. Ultimately, we present a unified rendering system for the visualization of entire geological models consisting of highly detailed stacked horizon surfaces and massive volume data. We demonstrate a single-pass ray casting approach facilitating correct visual interaction between distinct translucent model components, while increasing the rendering efficiency by reducing processing overhead of potentially invisible parts of the model. The combination of image-order rendering approaches and the level-of-detail feedback mechanism used by our out-of-core data-management system inherently accounts for occlusions of different data types without the application of costly culling techniques. The unified out-of-core data-management and virtualization infrastructure considerably facilitates the implementation of complex visualization systems. We demonstrate its applicability for the visualization of large geo-scientific data sets using output-sensitive rendering techniques. As a result, the magnitude and multitude of data sets that can be interactively visualized is significantly increased compared to existing approaches. KW - Computer Graphics KW - Visualisation KW - Volume Rendering KW - Large Data Y1 - 2013 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:gbv:wim2-20130725-19855 ER - TY - THES A1 - Salzmann, Holger T1 - Collaboration in Co-located Automotive Applications N2 - 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. N2 - Virtual-Reality-Systeme sind ein innovatives Instrument, um mit Hilfe computerbasierter Simulationen Entscheidungsprozesse zu unterstützen. Insbesondere in der Automobilbranche spielt diese Technologie eine wichtige Rolle, da heutzutage nahezu alle Fahrzeugteile in 3D konstruiert werden. Im Entwicklungsbereich der Automobilindustrie werden Visualisierungssysteme darüber hinaus bei der Untersuchung ergonomischer Aspekte von Montagevorgängen, bei der Bewertung der Mensch-Maschine-Schnittstelle im Fahrzeuginterieur, bei Designentscheidungen sowie bei Kundenpräsentationen eingesetzt. Diese Entscheidungsrunden bedürfen der Einbindung mehrerer Experten verschiedener Fachbereiche. Derzeit verfügbare stereoskopische Visualisierungssysteme ermöglichen aber nur einem Nutzer eine korrekte Stereosicht, während sich für die anderen Teilnehmer das 3D-Modell verzerrt darstellt. Dieser Nachteil ist ein wesentlicher Grund dafür, dass derartige Systeme bisher nur begrenzt im Automobilbereich anwendbar sind. Der Fokus dieser Dissertation liegt auf der Untersuchung der Anwendbarkeit stereoskopischer Mehrbenutzer-Systeme in verschiedenen Stadien des automobilen Entwicklungsprozesses. Derartige Systeme ermöglichen mehreren Nutzern gleichzeitig eine korrekte Stereosicht, was eine wesentliche Voraussetzung für die Zusammenarbeit in einer Gruppe darstellt. Die zentralen Forschungsfragen beziehen sich dabei auf die Anforderungen von kooperativen Entscheidungsprozessen sowie den daraus resultierenden Aspekten der Interaktion wie verbale Kommunikation, Gesten sowie virtuelle Menschmodelle und Interaktionstechniken zwischen den Nutzern. Die Arbeit belegt, dass stereoskopische Mehrbenutzersysteme die Anwendbarkeit virtueller Techniken im Automobilbereich entscheidend verbessern, da sie eine natürliche Kommunikation zwischen den Nutzern fördern. So ist die Unterstützung natürlicher Gesten beispielsweise ein wichtiger Faktor und es wird dargelegt, welche Genauigkeit beim Zeigen mit der realen Hand auf virtuelle Objekte erwartet werden kann. Darüber hinaus werden Anforderungen an virtuelle Menschmodelle anhand einer Zweibenutzer-Sitzkiste identifiziert und untersucht. Diese Form der Simulation, bei der die Nutzer nebeneinander in einem Fahrzeugmodell sitzen, dient vor allem der Bewertung von Mensch-Maschine-Schnittstellen im Fahrzeuginterieur. Des Weiteren wird das neue Konzept eines Mehrbenutzer-Werkzeugs in die Arbeit mit einbezogen, da hier verdeutlicht wird wie die Simulation von Montagevorgängen in virtuellen Umgebungen mit passivem haptischem Feedback zu ergonomischen Verbesserungen entsprechender Arbeitsvorgänge in der Realität beitragen kann. Diese Konzepte veranschaulichen wie VR-Systeme zur Unterstützung kollaborativer Prozesse in der Automobilbranche und darüber hinaus eingesetzt werden können. T2 - Zusammenarbeit in virtuellen Gruppenszenarien in der automobilen Entwicklung KW - Virtuelle Realität KW - Immersion KW - Simulation KW - Computergraphik KW - Virtual Reality KW - Computer Graphics KW - Interaction Techniques KW - Collaboration Y1 - 2010 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:gbv:wim2-20100712-15102 ER -