Este trabalho apresenta uma nova técnica de visualização que aproveita as vantagens do rendering volumétrico direto e do rendering de superfícies em um ambiente híbrido. O método faz uso de uma pré-visualização sobre o bordo do volume que viabiliza uma interação em tempo real com objetos volumétricos modelados por meio de malhas não estruturadas. Além disso, essa nova abordagem de visualização é paralelizável e pode se acelerada com placas gráficas comuns. / This work presents a new visualization technique that exploits the advantages of direct volume rendering and surface rendering in a hybrid environment. The method developed here makes use of a pre-visualization on the volume boundary to enable real time interaction with unstructured volumetric meshes. Furthermore, this new visualization approach can be implemented on existing parallel architectures and speed up by conventional graphical hardware.

[pt] Ray-Casting é uma técnica muito usada em visualizção volumétrica para a criação de imagens médicas, a partir de dados obtidos por ressonância magnética (MRI) e tomografias computadorizadas (CT). No entanto, ray- casting tem um alto custo computacional que resulta em um processo de visualização lento, o que compromete a interatividade necessária para uma boa compreensão do conjunto de dados tri-dimensionais.Este trabalho propõe estratégias para a otimização do algoritmo de ray-casting e para melhorar sua eficiência. Além disso, esta tese investiga o uso em um ambiente de computação distribuída, através de um protocolo de comunicação entre estações de trabalho heterogêneas e não dedicadas, conectadas em uma rede local.As idéias propostas foram implementadas em duas versões do algoritmo, uma sequencial e uma paralela. Os resultados obtidos com essas implementações em conjuntos de dados reais mostram que é possível obter tempo interativo com as máquinas disponíveis atualmente e em condições normais de uso da rede local por outros usuários. / [en] Ray-Casting is a useful volume visualization technique applied to medical images such as computer tomography (CT) and magnetic resonance image (MRI). It has, however, a high computational cost that results in a slow rendering process, which compromises the interactivity that is necessary for a good comprehension of the three-dimensional data set. This work proposes optimization strategies to the ray- casting algorithm to improve its effciency. To enhance, even further, the thesis investigates the use of a distributed computer environment through a communication protocol between heterogeneous and non- dedicate LAN-connected workstations. The ideas proposed here were implemented in two versions of the algorithm, one se- quential and one parallel. Test results, obtained with these implementations and real data sets, show that it is possible to obtain interactive time with the current available machines.

Este trabalho apresenta uma nova técnica de visualização que aproveita as vantagens do rendering volumétrico direto e do rendering de superfícies em um ambiente híbrido. O método faz uso de uma pré-visualização sobre o bordo do volume que viabiliza uma interação em tempo real com objetos volumétricos modelados por meio de malhas não estruturadas. Além disso, essa nova abordagem de visualização é paralelizável e pode se acelerada com placas gráficas comuns. / This work presents a new visualization technique that exploits the advantages of direct volume rendering and surface rendering in a hybrid environment. The method developed here makes use of a pre-visualization on the volume boundary to enable real time interaction with unstructured volumetric meshes. Furthermore, this new visualization approach can be implemented on existing parallel architectures and speed up by conventional graphical hardware.

Volume rendering is a research area within scientific visualisation, where images are computed from volumetric data sets for visual exploration. Such data sets are typically generated by Computer aided Tomography, Magnetic Resonance Imaging, Positron Emission Tomography or gained from simulations. The data sets are usually interpreted using optical models that assign optical properties to the volume and define the illumination and shading behaviour. Volume rendering techniques may be divided into three classes: object-order, image-order or hybrid methods. Image-order or ray casting methods shoot rays from the view plane into the volume and simulate the variation of light intensities along those rays. Object-order techniques traverse the volume data set and project each volume element onto the view plane. Hybrid volume rendering techniques combine these two approaches. A very popular object-order rendering method is called splatting. This technique traverses the volume data set and projects the optical properties of each volume element onto the view plane. This thesis consists of two parts. The first part introduces two new splatting methods, collectively called high-resolution splatting, which are based on standard splatting. Both high-resolution splatting methods correct errors of splatting by applying major modifications. We propose the first method, called fast high-resolution splatting, as an alternative to standard splatting. It may be used for quick previewing, since it is faster than standard splatting and the resulting images are significantly sharper. Our second method, called complete high-resolution splatting, improves the volume reconstruction, which results in images that are very close to those produced by ray casting methods. The second part of the thesis incorporates wavelet analysis into high-resolution splatting. Wavelet analysis is a mathematical theory that decomposes volumes into multi-resolution hierarchies, which may be used to find coherence within volumes. The combination of wavelets with the high-resolution splatting method has the two advantages. Firstly the extended splatting method, called high-resolution wavelet splatting, can be directly applied to wavelet transformed volume data sets without performing an inverse transform. Secondly when visualising wavelet compressed volumes, only a small fraction of the wavelet coefficients need to be projected. For all three versions of the new high-resolution splatting method, complexity analyses, comprehensive error and performance analyses as well as implementation details are discussed.

Volume rendering is a research area within scientific visualisation, where images are computed from volumetric data sets for visual exploration. Such data sets are typically generated by Computer aided Tomography, Magnetic Resonance Imaging, Positron Emission Tomography or gained from simulations. The data sets are usually interpreted using optical models that assign optical properties to the volume and define the illumination and shading behaviour. Volume rendering techniques may be divided into three classes: object-order, image-order or hybrid methods. Image-order or ray casting methods shoot rays from the view plane into the volume and simulate the variation of light intensities along those rays. Object-order techniques traverse the volume data set and project each volume element onto the view plane. Hybrid volume rendering techniques combine these two approaches. A very popular object-order rendering method is called splatting. This technique traverses the volume data set and projects the optical properties of each volume element onto the view plane. This thesis consists of two parts. The first part introduces two new splatting methods, collectively called high-resolution splatting, which are based on standard splatting. Both high-resolution splatting methods correct errors of splatting by applying major modifications. We propose the first method, called fast high-resolution splatting, as an alternative to standard splatting. It may be used for quick previewing, since it is faster than standard splatting and the resulting images are significantly sharper. Our second method, called complete high-resolution splatting, improves the volume reconstruction, which results in images that are very close to those produced by ray casting methods. The second part of the thesis incorporates wavelet analysis into high-resolution splatting. Wavelet analysis is a mathematical theory that decomposes volumes into multi-resolution hierarchies, which may be used to find coherence within volumes. The combination of wavelets with the high-resolution splatting method has the two advantages. Firstly the extended splatting method, called high-resolution wavelet splatting, can be directly applied to wavelet transformed volume data sets without performing an inverse transform. Secondly when visualising wavelet compressed volumes, only a small fraction of the wavelet coefficients need to be projected. For all three versions of the new high-resolution splatting method, complexity analyses, comprehensive error and performance analyses as well as implementation details are discussed.

Volume rendering is a research area within scientific visualisation, where images are computed from volumetric data sets for visual exploration. Such data sets are typically generated by Computer aided Tomography, Magnetic Resonance Imaging, Positron Emission Tomography or gained from simulations. The data sets are usually interpreted using optical models that assign optical properties to the volume and define the illumination and shading behaviour. Volume rendering techniques may be divided into three classes: object-order, image-order or hybrid methods. Image-order or ray casting methods shoot rays from the view plane into the volume and simulate the variation of light intensities along those rays. Object-order techniques traverse the volume data set and project each volume element onto the view plane. Hybrid volume rendering techniques combine these two approaches. A very popular object-order rendering method is called splatting. This technique traverses the volume data set and projects the optical properties of each volume element onto the view plane. This thesis consists of two parts. The first part introduces two new splatting methods, collectively called high-resolution splatting, which are based on standard splatting. Both high-resolution splatting methods correct errors of splatting by applying major modifications. We propose the first method, called fast high-resolution splatting, as an alternative to standard splatting. It may be used for quick previewing, since it is faster than standard splatting and the resulting images are significantly sharper. Our second method, called complete high-resolution splatting, improves the volume reconstruction, which results in images that are very close to those produced by ray casting methods. The second part of the thesis incorporates wavelet analysis into high-resolution splatting. Wavelet analysis is a mathematical theory that decomposes volumes into multi-resolution hierarchies, which may be used to find coherence within volumes. The combination of wavelets with the high-resolution splatting method has the two advantages. Firstly the extended splatting method, called high-resolution wavelet splatting, can be directly applied to wavelet transformed volume data sets without performing an inverse transform. Secondly when visualising wavelet compressed volumes, only a small fraction of the wavelet coefficients need to be projected. For all three versions of the new high-resolution splatting method, complexity analyses, comprehensive error and performance analyses as well as implementation details are discussed.

Volume rendering is a research area within scientific visualisation, where images are computed from volumetric data sets for visual exploration. Such data sets are typically generated by Computer aided Tomography, Magnetic Resonance Imaging, Positron Emission Tomography or gained from simulations. The data sets are usually interpreted using optical models that assign optical properties to the volume and define the illumination and shading behaviour. Volume rendering techniques may be divided into three classes: object-order, image-order or hybrid methods. Image-order or ray casting methods shoot rays from the view plane into the volume and simulate the variation of light intensities along those rays. Object-order techniques traverse the volume data set and project each volume element onto the view plane. Hybrid volume rendering techniques combine these two approaches. A very popular object-order rendering method is called splatting. This technique traverses the volume data set and projects the optical properties of each volume element onto the view plane. This thesis consists of two parts. The first part introduces two new splatting methods, collectively called high-resolution splatting, which are based on standard splatting. Both high-resolution splatting methods correct errors of splatting by applying major modifications. We propose the first method, called fast high-resolution splatting, as an alternative to standard splatting. It may be used for quick previewing, since it is faster than standard splatting and the resulting images are significantly sharper. Our second method, called complete high-resolution splatting, improves the volume reconstruction, which results in images that are very close to those produced by ray casting methods. The second part of the thesis incorporates wavelet analysis into high-resolution splatting. Wavelet analysis is a mathematical theory that decomposes volumes into multi-resolution hierarchies, which may be used to find coherence within volumes. The combination of wavelets with the high-resolution splatting method has the two advantages. Firstly the extended splatting method, called high-resolution wavelet splatting, can be directly applied to wavelet transformed volume data sets without performing an inverse transform. Secondly when visualising wavelet compressed volumes, only a small fraction of the wavelet coefficients need to be projected. For all three versions of the new high-resolution splatting method, complexity analyses, comprehensive error and performance analyses as well as implementation details are discussed.

Mannheim, Univ., Diss., 2008.

Mannheim, Univ., Diss., 2008.

[pt] O principal objetivo deste trabalho é apresentar um novo método para visualização de variedades implícitas de dimensão 3 mergulhadas no R4. Esse método consiste primeiramente de um pré-processamento em CPU utilizando uma árvore 16-Tree e a Aritmética Intervalar para encontrar as regiões do domínio onde a variedade se encontra. Esses dados são posteriormente processados em GPU para efetuar a visualização, e para isso foi utilizada uma generalização da técnica Ray Casting. / [en] The main objective of this work is to present a new method for the visualization of implicit 3-manifolds in R4. This method consists primarily of a preprocessing in the CPU using a 16-tree and Interval Arithmetic to detect regions of the domain where the variety is present. These data are then processed in the GPU to perform the visualization, and for this a generalization of Ray Casting technique was adopted.