<p>The purpose of this study is to determine if Virtual Reality safety training is more effective at teaching fall protection safety than traditional methods of instruction. A literature review of previous research was conducted and a theoretical framework and methodology was developed to test the two groups for this study. The research design is a difference-in-differences method comparing the pre-test and post-test scores of the participants of each group. There will be other small pieces of analysis that will be done to further understand the results of the data collection. The data will be analyzed and interpreted to better understand how the research question was answered in comparison to previous work and the theoretical framework. Finally, other questions that arose during the process will be addressed and future areas for more research will be defined.</p>

A complexidade dos sistemas de visualização imersivos pode variar tremendamente conforme a sua aplicação. Algumas ferramentas mais simples fazem uso de um único óculos de Realidade Virtual como infraestrutura de visualização. No entanto, aplicações mais complexas, como simuladores e outras ferramentas de treinamento, podem necessitar de uma infraestrutura distribuída, contendo diversos computadores e telas. Alguns simuladores e outras aplicações de treinamento fazem uso frequente de periféricos sofisticados de interação, que reproduzem de maneira fiel os elementos encontrados no cenário real. Além disto, o espaço de treinamento pode ser compartilhado por dois ou mais usuários. Estes requisitos acabam por impor o uso de sistemas de visualização complexos e distribuídos, que visam cobrir de maneira quase completa o campo de vis~ao destes usuários. Por causa das características deste tipo de sistema, as aplicações desenvolvidas nestes cenários são inerentemente complexas, pois frequentemente consideram aspectos específicos da infraestrutura para realizar a distribuição e o sincronismo da cena virtual. Esta complexidade dificulta o desenvolvimento, a manutenção e a interoperabilidade destas ferramentas. Este trabalho apresenta uma arquitetura de comunicação para promover o uso de sistemas imersivos de forma simples e transparente para as aplicações, viabilizando o uso de infraestruturas complexas e distribuídas. A arquitetura proposta utiliza o mecanismo de substituição do driver OpenGL para obter, de forma automática, a distribuição do aspecto gráfico das aplicações. Apesar deste conceito já ter sido discutido na literatura, esta proposta apresenta um conjunto de técnicas para contornar as limitações inerentes desta abordagem e obter ganhos de desempenho significativos, com resultados consistentes em um amplo conjunto de infraestruturas. As técnicas apresentadas neste trabalho sugerem, entre outras coisas, o uso de recursos modernos do padrão OpenGL para reduzir o volume de comunicação entre CPU e GPU. Um dos recursos avaliados foi o uso de mecanismos de renderização indireta, onde a aplicação armazena os comandos de renderização na memória da placa gráfica. Juntamente com esta técnica, o trabalho também investigou o uso de um algoritmo de culling na própria GPU, o que permitiu que esta otimização fosse utilizada mesmo em sistemas com arranjos mais complexos de tela. Os resultados obtidos mostram que a aplicação pode exibir o seu conteúdo em um conjunto amplo de sistemas imersivos, contendo mais resolução e mais geometria visível, sem deteriorar o seu desempenho. Os testes foram conduzidos em diferentes infraestruturas e com cenas de tamanhos variáveis. Nos casos mais complexos, as técnicas propostas podem reduzir em 86% o tempo médio de renderização, quando comparadas com as abordagens tradicionais. / The complexity of immersive visualization systems can vary tremendously depending on their application. Some simple tools might only require a conventional virtual reality goggle as a visualization infrastructure. However, more complex applications, such as simulators and other training tools, might require a distributed infrastructure, containing several computers and screens. Some training applications and simulators invariably make use of physical peripherals for interaction, which are designed to faithfully reproduce the elements found in real scenarios. Furthermore, the training area may be shared by two or more users. These requirements usually impose the use of complex and distributed imaging systems, which are intended to cover almost the entire field of view of the users involved. Because of the characteristics of this type of system, the applications developed for these infrastructures are inherently complex. They are required to consider specific aspects of the infrastructure itself to carry out the distribution and synchronization of the virtual scene. This complexity hampers the development, maintenance and interoperability of these tools. This work presents a communication architecture to promote the use of immersive systems by allowing applications to use complex and distributed infrastructures in a simple and transparent way. The proposed architecture uses the approach of replacing the OpenGL driver to transparently achieve graphics distribution. Although this has already been discussed in the literature, this document presents a set of techniques to overcome the inherent limitations of this approach and ultimately achieve significant performance gains, with consistent results across a broad range of infrastructures. The techniques presented here suggest, among other things, the use of modern features of the OpenGL standard to reduce the communication overhead between CPU and GPU. One of the features evaluated was the usage of indirect rendering, where the application stores all the rendering commands in the graphics card dedicated memory. Along with this feature, the work also investigated the use of a culling algorithm on the GPU itself, which allowed this optimization to be used even on systems containing screens with a more complex layout. The results show that the application can render its content in a wide range of immersive systems, with higher resolution and more visible geometry, without degrading its performance. The tests were conducted at different infrastructures and scenes with variable sizes. In the more complex use cases, the proposed techniques can reduce by up to 86% the average rendering time, when compared to the traditional approaches.

Made available in DSpace on 2015-03-04T18:57:55Z (GMT). No. of bitstreams: 1 DissertacaoEllenCorrea.pdf: 9749144 bytes, checksum: 89fe6968016fd6c546c16b922bf067c5 (MD5) Previous issue date: 2012-08-09 / This work describes the fundamental elements of medical simulations. It also documents a medical training prototype that was developed. Such prototype is composed of 3d models of a surgery room, anatomical models of a patient as well as models of a medical crew. The prototype also allows one to perform actions linked to the medical training of the pleural puncture. Finally, the prototype contains an evaluation agent that verifies the performance of the users while performing the medical procedure. This work goes on to evaluate the usability of a head mounted display in a medical simulation when compared with a simpler solution that uses just a LCD display. / Este trabalho descreve os elementos fundamentais para a construção de um sistema para simulação médica e o desenvolvimento de um protótipo de um ambiente de realidade virtual para treinamento médico. O protótipo inclui modelos 3D de uma sala de cirurgia, da anatomia do paciente virtual e da equipe médica, bem como os módulos de software necessários para simular o treinamento médico no protocolo do procedimento de punção pleural. O sistema possui ainda um agente avaliador capaz de acompanhar o desempenho dos usuários nas etapas necessárias do procedimento médico. Além disso, avaliamos a usabilidade de um capacete de realidade virtual neste tipo de aplicação, através de testes comparativos com uma solução mais simples que utiliza apenas um monitor convencional como saída de vídeo.

So, King-yan Oldfield. / Thesis (M.Phil.)--Chinese University of Hong Kong, 1999. / Includes bibliographical references (leaves 68-70). / Abstracts in English and Chinese. / Abstract --- p.i / Acknowledgments --- p.ii / Chapter 1 --- Introduction --- p.1 / Chapter 1.1 --- Evolution of Communication Technologies --- p.1 / Chapter 1.2 --- The Internet --- p.2 / Chapter 1.3 --- The Distributed Virtual Environments --- p.2 / Chapter 1.3.1 --- Features of DVE --- p.3 / Chapter 1.3.2 --- Current and Potential Applications --- p.4 / Chapter 1.3.3 --- The Challenges --- p.5 / Chapter 1.4 --- Our Contributions --- p.6 / Chapter 2 --- System Architecture --- p.7 / Chapter 2.1 --- The SSDVE and MSDVE Architectures --- p.7 / Chapter 2.2 --- Issues in the MSDVE Architecture --- p.8 / Chapter 2.2.1 --- On the Server Side --- p.8 / Chapter 2.2.2 --- On the Client Side --- p.8 / Chapter 3 --- Balancing Work Load and Reducing Inter-server Communication --- p.10 / Chapter 3.1 --- Problem Formulation --- p.10 / Chapter 3.1.1 --- The Area of Interest --- p.11 / Chapter 3.1.2 --- The DVE Cells --- p.11 / Chapter 3.1.3 --- Expected Number of Avatars --- p.12 / Chapter 3.1.4 --- Cost Metrics in Different Types of Network --- p.13 / Chapter 3.1.5 --- Problem Definition --- p.14 / Chapter 3.1.6 --- Complexity --- p.18 / Chapter 3.2 --- Partitioning Algorithms --- p.19 / Chapter 3.2.1 --- A Simplified Case --- p.19 / Chapter 3.2.2 --- The General Case --- p.19 / Chapter 3.3 --- Experiments --- p.22 / Chapter 4 --- Communication Sub-graph --- p.31 / Chapter 4.1 --- Problem Formulation --- p.31 / Chapter 4.1.1 --- Optimization Metrics --- p.32 / Chapter 4.1.2 --- Design Considerations --- p.32 / Chapter 4.2 --- Communication Sub-graph Construction Algorithms --- p.34 / Chapter 4.2.1 --- The Minimum Diameter Sub-graph (MDS) --- p.34 / Chapter 4.2.2 --- The Core-based Tree (CBT) --- p.37 / Chapter 4.2.3 --- The Minimum Spanning Tree (MST) --- p.40 / Chapter 5 --- Synchronization --- p.42 / Chapter 5.1 --- Synchronization in a DVE System --- p.43 / Chapter 5.2 --- System Model --- p.46 / Chapter 5.2.1 --- Problem Definition --- p.47 / Chapter 5.2.2 --- The Markov Chain Model --- p.47 / Chapter 5.2.3 --- Deciding the Threshold Φ --- p.49 / Chapter 5.3 --- Optimal Synchronizing Interval --- p.50 / Chapter 5.3.1 --- "An ""on-average"" Guarantee" --- p.50 / Chapter 5.3.2 --- A Stochastic Guarantee --- p.52 / Chapter 5.3.3 --- Finding p with T and Φ --- p.52 / Chapter 5.3.4 --- Searching for r*p --- p.54 / Chapter 5.4 --- Experiments --- p.55 / Chapter 5.4.1 --- Simulation Results --- p.55 / Chapter 5.4.2 --- Theoretical Results --- p.58 / Chapter 6 --- Related Work --- p.63 / Chapter 6.1 --- Load Balancing on DVE --- p.63 / Chapter 6.2 --- Object State Synchronization Techniques --- p.63 / Chapter 6.3 --- Group Communication and Multicasting --- p.64 / Chapter 6.4 --- DVE System Development Toolkits --- p.64 / Chapter 6.5 --- Example DVE Systems --- p.65 / Chapter 7 --- Conclusion --- p.66 / Chapter 7.1 --- A Vision to the Future --- p.66 / Chapter 7.2 --- Conclusion --- p.66 / Bibliography --- p.68

Chan Ming-fei. / Thesis (M.Phil.)--Chinese University of Hong Kong, 1999. / Includes bibliographical references (leaves 63-66). / Abstract --- p.i / Acknowledgments --- p.iii / Chapter 1 --- Introduction --- p.1 / Chapter 1.1 --- Challenging Issues --- p.2 / Chapter 1.2 --- Previous Work --- p.4 / Chapter 1.3 --- Organization of the Thesis --- p.5 / Chapter 2 --- Distributed Virtual Environment --- p.6 / Chapter 2.1 --- Possible Architectures --- p.6 / Chapter 2.2 --- Representations of Clients as Avatars --- p.7 / Chapter 2.3 --- Dynamic Membership --- p.9 / Chapter 3 --- Bandwidth and Computation Reduction Techniques --- p.11 / Chapter 3.1 --- Network Communication --- p.12 / Chapter 3.2 --- Dead Reckoning --- p.13 / Chapter 3.3 --- Message Aggregation --- p.15 / Chapter 3.3.1 --- Network-Based Aggregation --- p.15 / Chapter 3.3.2 --- Organization-Based Aggregations --- p.16 / Chapter 3.3.3 --- Grid-Based Aggregations --- p.16 / Chapter 3.4 --- Relevance Filtering --- p.17 / Chapter 3.4.1 --- Entity-Based Filtering --- p.17 / Chapter 3.4.2 --- Grid-Based Filtering --- p.19 / Chapter 3.5 --- Quiescent Entities --- p.20 / Chapter 3.6 --- Spatial Partitioning --- p.21 / Chapter 3.6.1 --- Necessity of Spatial Partitioning --- p.22 / Chapter 3.6.2 --- Binary Space Partitioning Tree --- p.23 / Chapter 3.6.3 --- BSP Tree Construction --- p.23 / Chapter 4 --- Partitioning Algorithm --- p.25 / Chapter 4.1 --- Problem Formulation --- p.25 / Chapter 4.2 --- Exhaustive Partition (EP) Algorithm --- p.28 / Chapter 4.3 --- Partitioning Algorithm --- p.29 / Chapter 4.3.1 --- Recursive Bisection Partition (RBP) Algorithm --- p.30 / Chapter 4.3.2 --- Layering Partitioning (LP) Algorithm --- p.32 / Chapter 4.3.3 --- Communication Refinement Partitioning (CRP) Algorithm --- p.38 / Chapter 4.4 --- Parallel Approach --- p.42 / Chapter 4.5 --- Further Observation --- p.43 / Chapter 5 --- Experiments --- p.44 / Chapter 5.1 --- Experiment 1: Small Virtual World --- p.45 / Chapter 5.2 --- Experiment 2: Large Virtual World --- p.46 / Chapter 5.3 --- Experiment 3: Moving of Avatars --- p.47 / Chapter 5.4 --- Experiment 4: Dynamic Joining and Leaving --- p.48 / Chapter 5.5 --- Experiment 5: Parallel Approach --- p.49 / Chapter 6 --- Implementation Considerations --- p.55 / Chapter 6.1 --- Different Environments --- p.55 / Chapter 6.2 --- Platform --- p.56 / Chapter 6.3 --- Lessons learned --- p.57 / Chapter 7 --- Conclusion --- p.59 / A Simplex Method --- p.60 / Bibliography --- p.63

Ka Keung Caramon Lee. / Thesis (M.Phil.)--Chinese University of Hong Kong, 2000. / Includes bibliographical references (leaves 100-105). / Abstracts in English and Chinese. / Contents --- p.iii / List of Figures --- p.vi / List of Tables --- p.ix / Chapter 1 --- Introduction --- p.1 / Chapter 1.1 --- Motivation --- p.1 / Chapter 1.2 --- Related Work --- p.3 / Chapter 1.2.1 --- Empirical Psychophysical Equations --- p.3 / Chapter 1.2.2 --- Industry Standards --- p.4 / Chapter 1.2.3 --- Fuzzy Logic --- p.4 / Chapter 1.2.4 --- Neural Networks --- p.5 / Chapter 1.3 --- Organization of Thesis --- p.7 / Chapter 2 --- Experimental Design --- p.9 / Chapter 2.1 --- Human Motion Sense --- p.9 / Chapter 2.2 --- Full-Body Motion Virtual Reality System --- p.12 / Chapter 2.3 --- Human Sensation Measure --- p.15 / Chapter 2.4 --- Trajectory Segmentation --- p.16 / Chapter 3 --- Learning and Validation of Human Sensation Models --- p.22 / Chapter 3.1 --- Cascade Neural Networks --- p.23 / Chapter 3.1.1 --- Dynamic Mapping --- p.26 / Chapter 3.2 --- Experimental Trajectory Data --- p.26 / Chapter 3.3 --- Effect of Trajectory Segmentation --- p.31 / Chapter 3.4 --- Model Validation --- p.32 / Chapter 3.5 --- Similarity Measure --- p.33 / Chapter 3.6 --- Similarity Measure Results --- p.38 / Chapter 4 --- Input Reduction for Human Sensation Modeling --- p.40 / Chapter 4.1 --- Introduction --- p.40 / Chapter 4.2 --- Input Reduction --- p.41 / Chapter 4.3 --- Feature Extraction and Input Selection --- p.42 / Chapter 4.4 --- Feature Extraction Using Principal Component Analysis --- p.44 / Chapter 4.5 --- Independent Component Analysis --- p.48 / Chapter 4.5.1 --- Measure of Gaussianity --- p.50 / Chapter 4.5.2 --- The Fixed Point ICA Algorithm --- p.51 / Chapter 4.6 --- Input Reduction Using Independent Component Analysis --- p.52 / Chapter 4.6.1 --- ICA Without Dimension Reduction --- p.52 / Chapter 4.6.2 --- Feature Extraction Using ICA --- p.55 / Chapter 4.6.3 --- Input Selection Using ICA --- p.57 / Chapter 4.6.4 --- Applying Input Selection by ICA on the Furnace Data --- p.58 / Chapter 4.6.5 --- Applying Input Selection by ICA to Sensation Modeling --- p.65 / Chapter 4.6.6 --- Cross Verification of Selected Inputs --- p.70 / Chapter 4.7 --- Summary on Input Reduction for Human Sensation Modeling --- p.72 / Chapter 5 --- Stimulus Modification Based on Human Sensation --- p.74 / Chapter 5.1 --- Need for Stimulus Modification --- p.74 / Chapter 5.2 --- Sensation Grades --- p.75 / Chapter 5.3 --- Trajectory Modification Scheme --- p.77 / Chapter 5.4 --- Experiments --- p.80 / Chapter 6 --- Conclusion --- p.86 / Chapter 6.1 --- Contributions --- p.86 / Chapter 6.2 --- Future Work --- p.87 / Chapter A --- Platform Model --- p.88 / Chapter A.1 --- Inverse Kinematics --- p.90 / Chapter A.2 --- Forward Kinematics --- p.93 / Chapter A.3 --- Platform Dynamics --- p.99 / Bibliography --- p.100

Ma Mun Chung. / Thesis (M.Phil.)--Chinese University of Hong Kong, 1998. / Includes bibliographical references (leaves 86-88). / Abstract also in Chinese. / Abstract --- p.i / Declaration --- p.ii / Acknowledgement --- p.iii / List of Figures --- p.iv / List of Tables --- p.ix / Table of Contents --- p.x / Chapter 1. --- Introduction --- p.1 / Chapter 1.1. --- Motivation --- p.1 / Chapter 1.2. --- Thesis Roadmap --- p.3 / Chapter 1.3. --- Contribution / Chapter 2. --- System Architecture --- p.6 / Chapter 2.1. --- Tracker system --- p.6 / Chapter 2.1.1. --- Spatial Information --- p.6 / Chapter 2.1.2. --- Transmitter (Xmtr) --- p.6 / Chapter 2.1.3. --- Receiver (Recvr) --- p.7 / Chapter 2.2. --- Glove System --- p.7 / Chapter 2.2.1. --- CyberGlove Interface Unit (CGIU) --- p.7 / Chapter 2.2.2. --- Bend Sensors --- p.7 / Chapter 2.3. --- Integrating the tracker and the glove system --- p.9 / Chapter 2.3.1. --- System Layout --- p.9 / Chapter 3. --- Deformable Model --- p.11 / Chapter 3.1. --- Elastic models in computer --- p.11 / Chapter 3.2. --- Virtual object model --- p.17 / Chapter 3.3. --- Force displacement relationship --- p.18 / Chapter 3.3.1. --- Stress-strain relationship --- p.19 / Chapter 3.3.2. --- Stiffness matrix formulation --- p.20 / Chapter 3.4. --- Solving the linear system --- p.24 / Chapter 3.5. --- Implementation --- p.26 / Chapter 3.5.1. --- Data structure --- p.26 / Chapter 3.5.2. --- Global stiffness matrix formulation --- p.27 / Chapter 3.5.3. --- Re-assemble of nodal displacement --- p.30 / Chapter 4. --- Collision Detection --- p.32 / Chapter 4.1. --- Related Work --- p.31 / Chapter 4.2. --- Spatial Subdivision --- p.37 / Chapter 4.3. --- Hierarchy construction --- p.38 / Chapter 4.3.1. --- Data structure --- p.39 / Chapter 4.3.2. --- Initialisation --- p.41 / Chapter 4.3.3. --- Expanding the hierarchy --- p.42 / Chapter 4.4. --- Collision detection --- p.45 / Chapter 4.4.1. --- Hand Approximation --- p.45 / Chapter 4.4.2. --- Interference tests --- p.47 / Chapter 4.4.3. --- Searching the hierarchy --- p.51 / Chapter 4.4.4. --- Exact interference test --- p.51 / Chapter 4.5. --- Grasping mode --- p.53 / Chapter 4.5.1. --- Conditions for Finite Element Analysis (FEA) --- p.53 / Chapter 4.5.2. --- Attaching conditions --- p.53 / Chapter 4.5.3. --- Collision avoidance --- p.54 / Chapter 4.6. --- Repeating deformation in different orientation --- p.56 / Chapter 5. --- Enhancing performance --- p.59 / Chapter 5.1. --- Data communication --- p.60 / Chapter 5.1.1. --- Client-server model --- p.60 / Chapter 5.1.2. --- Internet protocol suite --- p.61 / Chapter 5.1.3. --- Berkeley socket --- p.61 / Chapter 5.1.4. --- Checksum problem --- p.62 / Chapter 5.2. --- Use of parallel tool --- p.62 / Chapter 5.2.1. --- Parallel code generation --- p.63 / Chapter 5.2.2. --- Optimising parallel code --- p.64 / Chapter 6. --- Implementation and Results --- p.65 / Chapter 6.1. --- Supporting functions --- p.65 / Chapter 6.1.1. --- Read file --- p.66 / Chapter 6.1.2. --- Keep shape --- p.67 / Chapter 6.1.3. --- Save as --- p.67 / Chapter 6.1.4. --- Exit --- p.67 / Chapter 6.2. --- Visual results --- p.67 / Chapter 6.3. --- An operation example --- p.75 / Chapter 6.4. --- Performance of parallel algorithm --- p.78 / Chapter 7. --- Conclusion and Future Work --- p.84 / Chapter 7.1. --- Conclusion --- p.84 / Chapter 7.2. --- Future Work --- p.84 / Reference --- p.86 / Appendix A Matrix Inversion --- p.89 / Appendix B Derivation of Equation 6.1 --- p.92 / Appendix C Derivation of (6.2) --- p.93

by Yu-Hang Siu. / Thesis (M.Phil.)--Chinese University of Hong Kong, 1998. / Includes bibliographical references (leaves 74-80). / Abstract also in Chinese. / Abstract --- p.iii / Acknowledgements --- p.v / Chapter 1 --- Introduction --- p.1 / Chapter 1.1 --- Volume Visualization --- p.2 / Chapter 1.2 --- Virtual Environment --- p.11 / Chapter 1.3 --- Approach --- p.12 / Chapter 1.4 --- Thesis Overview --- p.13 / Chapter 2 --- Contour Extraction --- p.15 / Chapter 2.1 --- Concept of Intelligent Scissors --- p.16 / Chapter 2.2 --- Dijkstra's Algorithm --- p.18 / Chapter 2.3 --- Cost Function --- p.20 / Chapter 2.4 --- Summary --- p.23 / Chapter 3 --- Volume Cutting --- p.24 / Chapter 3.1 --- Basic idea of the algorithm --- p.25 / Chapter 3.2 --- Intelligent Scissors on Surface Mesh --- p.27 / Chapter 3.3 --- Internal Cutting Surface --- p.29 / Chapter 3.4 --- Summary --- p.34 / Chapter 4 --- Three-dimensional Intelligent Scissors --- p.35 / Chapter 4.1 --- 3D Graph Construction --- p.36 / Chapter 4.2 --- Cost Function --- p.40 / Chapter 4.3 --- Applications --- p.42 / Chapter 4.3.1 --- Surface Extraction --- p.42 / Chapter 4.3.2 --- Vessel Tracking --- p.47 / Chapter 4.4 --- Summary --- p.49 / Chapter 5 --- Implementations in a Virtual Environment --- p.52 / Chapter 5.1 --- Volume Cutting --- p.53 / Chapter 5.2 --- Surface Extraction --- p.56 / Chapter 5.3 --- Vessel Tracking --- p.59 / Chapter 5.4 --- Summary --- p.64 / Chapter 6 --- Conclusions --- p.68 / Chapter 6.1 --- Summary of Results --- p.68 / Chapter 6.2 --- Future Directions --- p.70 / Chapter A --- Performance of Dijkstra's Shortest Path Algorithm --- p.72 / Chapter B --- IsoRegion Construction --- p.73

by Tsang Kwok Hang Elton. / Thesis submitted in: December 1998. / Thesis (M.Phil.)--Chinese University of Hong Kong, 1999. / Includes bibliographical references (leaves 78-83). / Abstract also in Chinese. / Chapter 1 --- Introduction --- p.1 / Chapter 2 --- Virtual-hand Recognition --- p.5 / Chapter 2.1 --- Hand model --- p.6 / Chapter 2.1.1 --- Hand structure --- p.6 / Chapter 2.1.2 --- Motions of the hand joints --- p.8 / Chapter 2.2 --- Hand-tracking technologies --- p.9 / Chapter 2.2.1 --- Glove-based tracking --- p.10 / Chapter 2.2.2 --- Image-based tracking --- p.12 / Chapter 2.3 --- Problems in virtual-hand recognition --- p.13 / Chapter 2.3.1 --- Hand complexity --- p.13 / Chapter 2.3.2 --- Human variations --- p.13 / Chapter 2.3.3 --- Immature hand-tracking technologies --- p.14 / Chapter 2.3.4 --- Time-varying signal --- p.14 / Chapter 2.3.5 --- Efficiency --- p.14 / Chapter 3 --- Previous Work --- p.16 / Chapter 3.1 --- Posture and gesture recognition algorithms --- p.16 / Chapter 3.1.1 --- Template Matching --- p.17 / Chapter 3.1.2 --- Neural networks --- p.18 / Chapter 3.1.3 --- Statistical classification --- p.20 / Chapter 3.1.4 --- Discontinuity matching --- p.21 / Chapter 3.1.5 --- Model-based analysis --- p.23 / Chapter 3.1.6 --- Hidden Markov Models --- p.23 / Chapter 3.2 --- Hand-input systems --- p.24 / Chapter 3.2.1 --- Gesture languages --- p.25 / Chapter 3.2.2 --- 3D modeling --- p.25 / Chapter 3.2.3 --- Medical visualization --- p.26 / Chapter 4 --- Posture Recognition --- p.28 / Chapter 4.1 --- Fuzzy concepts --- p.28 / Chapter 4.1.1 --- Degree of membership --- p.29 / Chapter 4.1.2 --- Certainty factor --- p.30 / Chapter 4.1.3 --- Evidence combination --- p.30 / Chapter 4.2 --- Fuzzy posture recognition system --- p.31 / Chapter 4.2.1 --- Objectives --- p.32 / Chapter 4.2.2 --- System overview --- p.32 / Chapter 4.2.3 --- Input parameters --- p.33 / Chapter 4.2.4 --- Posture database --- p.36 / Chapter 4.2.5 --- Classifier --- p.37 / Chapter 4.2.6 --- Identifier --- p.40 / Chapter 5 --- Performance Evaluation --- p.42 / Chapter 5.1 --- Experiments --- p.42 / Chapter 5.1.1 --- Accuracy analysis --- p.43 / Chapter 5.1.2 --- Efficiency analysis --- p.46 / Chapter 5.2 --- Discussion --- p.48 / Chapter 5.2.1 --- Strengths and weaknesses --- p.48 / Chapter 5.2.2 --- Summary --- p.50 / Chapter 6 --- Posture Database Editor --- p.51 / Chapter 6.1 --- System architecture --- p.51 / Chapter 6.1.1 --- Hardware configuration --- p.51 / Chapter 6.1.2 --- Software tools --- p.53 / Chapter 6.2 --- User interface --- p.54 / Chapter 6.2.1 --- Menu bar --- p.55 / Chapter 6.2.2 --- Working frame and data frame --- p.56 / Chapter 6.2.3 --- Control panel --- p.56 / Chapter 7 --- An Application: 3D Virtual World Modeler --- p.59 / Chapter 7.1 --- System Design --- p.60 / Chapter 7.2 --- Common operations --- p.62 / Chapter 7.3 --- Virtual VRML Worlds --- p.65 / Chapter 8 --- Conclusion --- p.70 / Chapter 8.1 --- Summaries on previous work --- p.70 / Chapter 8.2 --- Contributions --- p.73 / Chapter 9 --- Future Work --- p.75 / Bibliography --- p.78

Through immersive stereoscopic displays and natural user interfaces, virtual reality (VR) is capable of offering the user a sense of presence in the virtual space, and has been long expected to revolutionize how people interact with virtual content in various application scenarios. However, with many technical challenges solved over the last three decades to bring low cost and high fidelity to VR experiences, we still do not see VR technology used frequently in many seemingly suitable applications. Part of this is due to the lack of expressiveness and efficiency of traditional “simple and reality-based� 3D user interfaces (3DUIs). The challenge is especially obvious when complex interaction tasks with diverse requirements are involved, such as editing virtual objects from multiple scales, angles, perspectives, reference frames, and dimensions. A common approach to overcome such problems is through hybrid user interface (HUI) systems that combine complementary interface elements to leverage their strengths. Based on this method, the first contribution of this dissertation is the proposal of Force Extension, an interaction technique that seamlessly integrates position-controlled touch and rate-controlled force input for efficient multi-touch interaction in virtual environments. Using carefully designed mapping functions, it is capable of offering fluid transitions between the two contexts, as well as simulating shear force input realistically for multi-touch gestures. The second contribution extends the HUI concept into immersive VR by introducing a Hybrid Virtual Environment (HVE) level editing system that combines a tablet and a Head-Mounted Display (HMD). The HVE system improves user performance and experience in complex high-level world editing tasks by using a “World-In-Miniature� and 2D GUI rendered on a multi-touch tablet device to compensate for the interaction limitations of a traditional HMD- and wand-based VR system. The concept of Interaction Context (IC) is introduced to explain the relationship between tablet interaction and the immersive interaction, and four coordination mechanisms are proposed to keep the perceptual, functional, and cognitive flow continuous during IC transitions. To offer intuitive and realistic interaction experiences, most immersive 3DUIs are centered on the user’s virtual avatar, and obey the same physics rules of the real world. However, this design paradigm also employs unnecessary limitations that hinders the performance of certain tasks, such as selecting objects in cluttered space, manipulating objects in six degrees of freedom, and inspecting remote spaces. The third contribution of this dissertation proposes the Object Impersonation technique, which breaks the common assumption that one can only immerse in the VE from a single avatar, and allows the user to impersonate objects in the VE and interact from their perspectives and reference frames. This hybrid solution of avatar- and object-based interaction blurs the line between travel and object selection, creating a unique cross-task interaction experience in the immersive environment. Many traditional 3DUIs in immersive VR use simple and intuitive interaction paradigms derived from real world metaphors. But they can be just as limiting and ineffective as in the real world. Using the coordinated HUI or HVE systems presented in this dissertation, one can benefit from the complementary advantages of multiple heterogeneous interfaces (Force Extension), VE representations (HVE Level Editor), and interaction techniques (Object Impersonation). This advances traditional 3D interaction into the more powerful hybrid space, and allows future VR systems to be applied in more application scenarios to provide not only presence, but also improved productivity in people’s everyday tasks.