Implementation and Analysis of an Image-Based Global Illumination Framework for Animated Environments

We describe a new framework for efficiently computing and storing global illumination effects for complex, animated environments. The new framework allows the rapid generation of sequences representing any arbitrary path in a view space within an environment in which both the viewer and objects move. The global illumination is stored as time sequences of range-images at base locations that span the view space. We present algorithms for determining locations for these base images, and the time steps required to adequately capture the effects of object motion. We also present algorithms for computing the global illumination in the base images that exploit spatial and temporal coherence by considering direct and indirect illumination separately. We discuss an initial implementation using the new framework. Results and analysis of our implementation demonstrate the effectiveness of the individual phases of the approach; we conclude with an application of the complete framework to a complex environment that includes object motion

Visualização de informação

O relatório está dividido em duas partes. Na primeira parte, é abordado o problema da visualização exactamente no que diz respeito à subtil correlação existente entre as técnicas (e respectivas metáforas), o utilizador e os dados. Na segunda parte, são analisadas algumas aplicações, projectos, ferramentas e sistemas de Visualização de Informação. Para categorizalos, serão considerados sete tipos de dados básicos subjacentes a eles: unidimensional, bidimensional, tridimensional, multi-dimensional, temporal, hierárquico, rede e workspace.O tema deste relatório é a visualização da informação. Esta é uma área actualmente muito activa e vital no ensino, na pesquisa e no desenvolvimento tecnológico. A ideia básica é utilizar imagens geradas pelo computador como meio para se obter uma maior compreensão e apreensão da informação que está presente nos dados (geometria) e suas relações (topologia). É um conceito simples, porém poderoso que tem criado imenso impacto em diversas áreas da engenharia e ciência.The theme of this report is information visualization. Nowadays, this is a very active and vital area of research, teaching and development. The basic idea of using computer generated pictures to gain information and understanding from data and relationships is the key concept behind it. This is an extremely simple, but very important concept which is having a powerful impact on methodology of engineering and science. This report is consisted of two parts. The first one, is an overview of the subtle correlation between the visual techniques, the user perception and the data. In the second part, several computer applications, tools, projects and information visualization systems are analyzed. In order to categorize them, seven basic types of data are considered: onedimensional, two- dimensional, three-dimensional, multidimensional, temporal, hierarchic, network and workspace

Giving eyes to ICT!, or How does a computer recognize a cow?

Het door Schouten en andere onderzoekers op het CWI ontwikkelde systeem berust op het beschrijven van beelden met behulp van fractale meetkunde. De menselijke waarneming blijkt mede daardoor zo efficiënt omdat zij sterk werkt met gelijkenissen. Het ligt dus voor de hand het te zoeken in wiskundige methoden die dat ook doen. Schouten heeft daarom beeldcodering met behulp van 'fractals' onderzocht. Fractals zijn zelfgelijkende meetkundige figuren, opgebouwd door herhaalde transformatie (iteratie) van een eenvoudig basispatroon, dat zich daardoor op steeds kleinere schalen vertakt. Op elk niveau van detaillering lijkt een fractal op zichzelf (Droste-effect). Met fractals kan men vrij eenvoudig bedrieglijk echte natuurvoorstellingen maken. Fractale beeldcodering gaat ervan uit dat het omgekeerde ook geldt: een beeld effectief opslaan in de vorm van de basispatronen van een klein aantal fractals, samen met het voorschrift hoe het oorspronkelijke beeld daaruit te reconstrueren. Het op het CWI in samenwerking met onderzoekers uit Leuven ontwikkelde systeem is mede gebaseerd op deze methode. ISBN 906196502

Interacting with a virtually deformable object using an instrumented glove.

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

A Study of Velocity-Dependent JND of Haptic Model Detail

The study of haptics, or the sense of touch in virtual reality environments, is constantly looking for improvements in modeling with a high fidelity. Highly detailed models are desirable, but they often lead to slow processing times, which can mean a loss of fidelity in the force feedback sensations. Model compression techniques are critical to balancing model detail and processing time. One of the proposed compression techniques is to create multiple models of the same object but with different levels of detail (LOD) for each model. The technique hypothesizes that the human arm loses sensitivity to forces with the increase of its movement speed. This the compression technique determines which model to use based on the user's movement speed. This dissertation examines studies how the movement speed of the user affects the user's ability to sense changes in details of haptic models. Experiments are conducted using different haptic surfaces. Their levels of detail are changed while the subject interacts with them to mimic the effects of a multiresolution compression implementation. The tests focus on the subjects' ability to differentiate changes of the surfaces at each speed. The first experiment uses curved surfaces with multiple resolutions. This test observes the sensitivity of the user when the details on the surface are small. The results show that the subjects are more sensitive to changes of small details at a lower speed than higher speed. The second experiment measures sensitivity to larger features by using trapezoidal surfaces with different angles. The trapezoidal surfaces can be seen as a low-resolution haptic model with only two vertices, and changing the angles of the trapezoids is seen as changing the radii of curvature. With the same speed settings from the first experiment applied to the subjects, the sensitivity for changes in curvature is predicted to decrease with the increase of speed. However, the results of this experiment proved otherwise. The conclusions suggest that multiresolution designs are not a straightforward reduction of LOD, even though the movement speed does affect haptic sensitivity. The model's geometry should be taken into account when designing the parameters for haptic model compression. The results from the experiments provide insights to future haptic multiresolution compression designs

Design reuse in a CAD environment

This thesis was submitted for the degree of Doctor of Philosophy and awarded by Brunel University, 09/03/1999.For many companies, design related information mainly exists as rooms of paper-based archives, typically in the form of manufacturing drawings and technical specifications. This 'static' information cannot be easily reused. The work presented in this thesis proposes a methodology to ease this problem. It defines and implements a computer-based design tool that will enable existing design families to be transformed into 'dynamic' CAD-based models for the Conceptual, Embodiment and Detailed stages of the design process. Two novel concepts are proposed here, i) the use of a Function Means Tree to store Conceptual and Embodiment design and ii) a Variant Method to represent Detailed design. In this way a definite link between the more abstract conceptual and the concrete detailed design stages is realised by linking individual detailed designs to means in the Function Means Tree. The use of the Variant Method, incorporating 'state-of-the-art' developments in Solid Modelling, Feature-Based Design and Parametric Design, allows an entire family of designs to be represented by a single Master Model. Therefore, instances of this Master Model need only be stored as a set of design parameters. This enables current design families and new design cases to be more created more efficiently. Industrial Case Studies, including a Lathe Chuck family, a Drive-End casting and a family of Filtration Systems are given to prove the methodology

CHUB: um modelo cartográfico para a visualização e análise do corpo humano

Tese de Doutoramento em Tecnologias e Sistemas de Informação - Área do Conhecimento Engenharia de Programação e dos Sistemas InformáticosA visualização é a representação visual realística ou abstracta de um conjunto de dados que são gerados por modelos computacionais ou resultantes de medições físicas realizadas no mundo real. É fundamental para auxiliar as pessoas a compreenderem dados e processos complexos e pode ser classificada consoante os seus objectivos (nomeadamente a visualização científica e de informação). A correcta modelação e caracterização dos dados são partes fundamentais para a escolha de técnicas visuais eficazes e a produção de uma visualização válida. O grande desafio é exactamente o de identificar como a análise dos resultados pode e deve ser mostrada ao potencial utilizador de uma forma simultaneamente sucinta, coerente e útil. O conceito de modelação cartográfica ou álgebra de mapas foi desenvolvido por Dana Tomlin em 1983 com o Map Analysis Package1 [Sendra2000]. Um modelo cartográfico pode ser visualizado como uma colecção de mapas registados numa base cartográfica comum, em que cada mapa é uma variável sujeita a operações matemáticas tradicionais. A modelação é um processo que decorre de operações primitivas de pontos, vizinhança e regiões sobre diferentes mapas, numa lógica sequencial para interpretar e resolver problemas espaciais. Neste contexto, a sequência de operações é similar à solução algébrica de um conjunto de equações. A criação de ferramentas informáticas para a análise e visualização de dados relacionados com o corpo humano é uma área em forte expansão e de especial interesse. Apesar destas ferramentas serem muito úteis, sofrem bastante da limitação imposta pela arquitectura dos modelos utilizados para o seu desenvolvimento e consequente implementação. Isto ocorre porque estes modelos adoptam os mesmos princípios e ponderações que são aplicados a dados de natureza não humana ou biológica e tratando-os de forma independente e atómica. Por outro lado, a utilização de técnicas visuais pouco intuitivas no sentido de denotar a interdependência espacial inerente a este tipo de informação é outra limitação a salientar neste tipo de ferramentas. Os dados relacionados com o corpo humano apresentam uma forte componente espacial. Para que seja possível uma análise e investigação correctas é necessário ter isso sempre em consideração. Um bom exemplo desta situação é o diagnóstico médico. A combinação de informação oriunda de diferentes partes do corpo humano é normalmente necessária para que um médico possa diagnosticar a doença de um paciente. O acto de diagnosticar pode ser traduzido por um conjunto de operações de álgebra de mapas executadas sobre os dados relacionados com o corpo humano do paciente. Qualquer modelo que pretenda servir de base para o desenvolvimento e implementação de ferramentas informáticas orientadas para a medicina, e em especial, para a análise e visualização de dados relacionado com o corpo humano, deve incorporar os princípios fundamentais da modelação cartográfica. Desta maneira, é possível que os dados possam ser devidamente modelados e consequentemente extrapolada mais informação útil. Por outro lado, a utilização da visualização como instrumento de comunicação de resultados, com a inclusão de metáforas visuais cartográficas é outra mais-valia a ter em conta. O modelo CHUB (Cartographic Human Body), que é apresentado neste trabalho, pretende colmatar essa falha identificada no tratamento e visualização de dados relacionados com o corpo humano. Utiliza a modelação cartográfica como alicerce fundamental para a análise dos dados e a visualização científica e de informação como meio para a comunicação de resultados. Para ser possível a sua avaliação e validação foram considerados dois estudos de caso: diagnóstico da artrose no joelho e a análise de sessões de hidrocinesioterapia. Para estes dois estudos de caso foi implementado um protótipo que instancia o modelo CHUB nestes casos particulares, permitindo a sua utilização, avaliação e validação em dois domínios específicos. Os resultados obtidos após a utilização e avaliação do protótipo permitiram validar com sucesso o modelo CHUB proposto nesta tese de doutoramento.Visualization is the realistic or abstract visual representation of a dataset that is generated by computer models or resulting from physical measurements of the real world. Visualization is fundamental to help people understand data and complexes processes and can be categorized according its goals (scientific or information). The correct data model and characterization are essential to the right choice of the visualization techniques and the production of useful visualizations. The great challenge lies in how to determine that the results are showed to the final users at the same time in a coherent, useful and simple way. The cartographic model concept was developed by Dana Tomlin in 1983 with the Map Analysis Package2 [Sendra2000]. A cartographic model can be seen as a collection of maps that are registered in a cartographic database, where each map is a “variable” that can be mathematically operated. These operations may involve primitives such as points or areas of different maps, for example, in a sequential order to interpret and solve spatial problems. In this context, the sequence of operations is similar to the algebraic solution of a group of equations. The creation of automatic tools for human’s body data analysis and visualization is a field in expansion and of great interest. However these tools are very valuable, they suffer from a common limitation that is imposed by their basis architectural model. In general, they rarely represent in a suitable way biological, morphological and/or biomedical data spatial interdependency. These models treat data in an almost total focused and independent way. The human body systems and organs work as a complex machine, where each part depends strongly on the others. This dependency might be stronger or weaker to the system or organ importance on the overall patient condition. The doctor diagnoses an illness by comparing and analyzing information not only directly related to the mostly affected organ, but also to the body as a whole. In fact the doctor performs a subtle spatial analysis, and therefore, executes a typical algebraic map operation in his/her mind, when diagnosing a patient. An illness might arouse different symptoms and physiological changes in systems/organs that are not directly related to the spatial location of it. CHUB is a model that was developed taking into consideration the main principles of cartographic modelling. It structures data according to different layers of information. Each layer is associated to a specific organ and/or system, and might contain geometric data or attributes that are “human-referenced”. CHUB has not been developed as a dynamic model. It is considered that dynamic issues related to human’s body data, such as body movement, blood flow or heartbeat (besides others) will be accomplished by other models that should be used as a specialized extension to CHUB. In order to validate CHUB two cases of study were considered – osteoarthritis knee diagnosis and hydrokinetic therapy sessions analysis, proposed two strategies for its validation and a prototype implemented. This prototype allowed its utilization, evaluation and validation in two different domains. The results achieved after its utilization and test lead to a complete CHUB validation