We investigate some problems commonly found when dealing with stereo images. Working within the context of visual effects for films, we explore software solutions to issues arising with stereo images captured on-set. These images originate from a wide variety of hardware which may or may not provide additional data support for post-production needs. Generic software solutions are thus greatly to be preferred. This dissertation documents contributions in the following three areas. Each project was undertaken at Double Negative and investigated with the aim of improving the post-production pipeline for 3D films. Colour matching is the process whereby the colours of one view from a stereo pair are matched with those of the other view. This process is necessary due to the fact that slight differences in hardware and viewing angle can result in some surprisingly large colour discrepancies. Chapter 3 presents a novel approach to colour matching between stereo pairs of images, with a new tool for visual effects artists given in section 6.2.Vertical alignment of stereo images is key to providing a comfortable experience for the viewer, yet we are rarely presented with perfectly aligned footage from the outset. In chapter 4 we discuss the importance of correcting misalignments for both the final audience and the artists working on these images. We provide a tool for correcting misalignments in section 6.3.Disparity maps are used in many areas of post-production, and so in chapter 5 we investigate ways in which disparity map generation can be improved for the benefit of many existing tools at Double Negative. In addition, we povide an extensive exploration of the requirements of 3D films in order to make them presentable in the cinema. Through these projects, we have provided improvements to the stereo workflow and shown that academic research is a necessary component of developing tools for the visual effects pipeline. We have provided new algorithms to improve the 3D experience for moviegoers, as well as artists, and conclude by discussing the future work that will provide further gains in the field.

Nos últimos anos a utilização de pontos como primitiva gráfica básica vem mostrandose uma poderosa e versátil ferramenta para a computação gráfica. Considerável esforço de pesquisa vem sendo dedicado para encontrar formas eficientes de aquisição, representação, processamento, renderização e animação para conjuntos de pontos. As representações baseadas em pontos têm-se destacado como uma estratégia eficiente em computação desde que se tornou comum extrair modelos geométricos a partir de Scanners 3D, os quais geram grandes quantidades de pontos que aproximam a geometria do objeto. Este trabalho apresenta um conjunto de métodos para tratar a visibilidade aproximada para nuvens de pontos sem informação de conectividade e topologia. Primeiramente é proposto uma abordagem baseada em clusters para acelerar o operador de remoção de pontos proposto por Katz et al. A principal motivação para esta otimização é a possibilidade de conseguir um equilíbrio entre a velocidade e a qualidade do resultado. Também é apresentado uma técnica de renderização baseada em pontos acelerada por hardware chamada Surface Splatting. Esta abordagem utiliza mapeamento de textura com alpha blending para aproximar um filtro de reamostragem Elliptical Weighted Average no espaço de objeto. Juntamente com o Geometry Shader das modernas placas gráficas, produz de forma eficiente imagens de alta qualidade de superfícies amostradas por surfels. Por último é proposto um novo operador de remoção de pontos ocultos acelerado por hardware baseados na técnica de splatting juntamente com um operador morfológico de erosão modificado para reduzir o efeito de silhuetas no resultado final do operador. A motivação para a criação deste novo operador é a baixa eficiência demonstrada pelos métodos existentes para a utilização em aplicações em tempo real onde as nuvens de pontos são muito densas. Todas as técnicas apresentadas neste trabalho podem ser utilizadas em visualização científica com taxas interativas, em particular na visualização direta de geometria baseada em pontos. / In recent years the use of points as a fundamental graphics primitive has proved to be a powerful and versatile tool for computer graphics. Considerable research has been devoted to the efficient representation, modeling, processing, rendering and animation of point-sampled geometry. The point-based representation has gained increasing attention in computer graphics because 3D scanning systems easily extract large information from real-world objects. On the other hand, point sets are more flexible when compared to triangle meshes, because they are not required to maintain consistent topological information. This work presents a set of tools to determine the visibility and also to render a point-based geometry efficiently. Firstly, a cluster-based approach is proposed to speed up the hidden point removal operator proposed by Katz et al. The main idea of this study is to trade-off speed and quality in dynamic scenes of moving or deforming point clouds. After that, a hardware based point rendering technique called Surface Splatting is introduced. This approach uses the texture mapping with alpha blending and the Geometry Shader to approximate the Elliptical Weighted Average filter in object space. This efficient technique produces high quality images as surfel-based geometry. Finally, a new hidden point removal operator is presented. This operator, based on the splatting technique and also hardware accelerated, applies a morphological erosion operation in the depth buffer to reduce the silhouette effect in the final image. The motivation to develop a new operator is the low efficiency demonstrated by existing hidden point removal methods in real time applications, where the point cloud is very dense. All the techniques introduced in this work can be used in scientific visualization with interactive frame rates, particularly when visualizing point-based geometry sets.

Malhas simpliciais são utilizadas em várias áreas da Computação Gráfica e Engenharia, como por exemplo, em vizualização, simulação, prototipação, além de outras aplicações. Este tipo de malha é, geralmente, utilizada como aproximações discretas de espaços contínuos, onde eles oferecem representações flexíveis e eficientes. Muito esforço é gasto visando gerar malhas de boa qualidade, porém, em alguns casos as malhas acabam sendo modificadas. Entretanto, este tipo de operação é geralmente custosa e inflexível, o que pode resultar na geraão de malhas bem diferentes das originais. A habilidade de manipular cenas dinâmicas revela-se um dos problemas mais desafiadores da computação gráfica. Este trabalho propõe um método alternativo para atualizar malhas simpliciais que vai além de mudanças geométricas e topológicas. Tal método explora uma das propriedade das Tringulações de Delaunay com Pesos, que permite a usá-las para definir implicitamente as relações de conectividade de uma malha. Ao contrário de manter as informações de conectividade explicitamente, a atual abordagem simplesmente armazena uma coleção de pesos associados a cada vértice. Além disso, criamos um algoritmo para calcular uma Tringulação de Delaunay com Pesos a partir de uma dada triangulação. O algoritmo consiste em uma busca em largura que atribui pesos aos vértices, e uma estratégia de de subdivisão para assegurar que a triangulação reconstruída será correspondente à original. Este método apresenta diversas aplicações e, em particular, permite a criação de um sistema simples de realizar combinação entre triangulações, que será ilustrada com exemplos em 2D e 3D. / Simplicial meshes are used in many fields of Computer Graphics and Engineering, for instance, in visualization, simulation, prototyping, among other applications. This kind of mesh is often used as discrete approximations of continuous spaces, where they offer flexible and efficient representations. Considerable effort is spent in generating good quality meshes, but in some applications the meshes can be modified over time. However, this kind of operation is often very expensive and inflexible, sometimes leading to results very different from the original meshes. The ability to handle dynamic scenes reveals itself as one of the most challenging problems in computer graphics. This work proposes an alternative technique for updating simplicial meshes that undergo geometric and topological changes. It explores the property that a Weighted Delaunay Triangulation (WDT) can be used to implicitly define the connectivity of a mesh. Instead of explicitly maintaining connectivity information, this approach simply keeps a collection of weights associated to each vertex. It consists of an algorithm to compute a WDT from any given triangulation, which relies on a breadth-first traversal to assign weights to vertices, and a subdivision strategy to ensure that the reconstructed triangulation conforms with the original one. This technique has many applications and, in particular, it allows for a very simple method of merging triangulations, which is illustrated with both 2D and 3d examples.

Métodos tradicionais de animação de fluidos têm dificuldade em resolver escoamentos que envolvem aberturas estreitas e geometrias finas. Abordagens anteriores artificialmente inflaram ou voxelizaram geometrias de objetos finos, sacrificando a geometria e topologias corretas do domínio de simulação, impedindo que o escoamento interaja corretamente com regiões estreitas. No trabalho desenvolvido, apresentamos uma técnica de simulação de fluidos que respeita geometrias complexas de maneira precisa e supera obstáculos comuns em ambientes com aberturas estreitas e geometrias finas. A nossa solução baseia-se no recorte preciso de células do grid regular, gerando uma malha conformal à geometria e topologicamente correta. Nós utilizamos uma abordagem de bordas incorporadas (cut-cells): em cada passo do tempo, a malha de triângulos representando a superfície sólida de um objeto no domínio de simulação é recortada pelas células que intercepta, potencialmente gerando múltiplas sub-células distintas. A malha resultante é conformal ao objeto incorporado e se reduz ao grid regular em regiões que não estão em contato com a superfície. Nós estendemos as abordagens tradicionais de advecção de velocidade e projeção da pressão para dar suporte a essa estrutura de malha aprimorada. Em geral, nossa abordagem é capaz de representar melhor detalhes de geometrias que são menores que uma célula do grid, corretamente recuperando condições de contorno no-slip e free-slip, enquanto mantém uma convergência para a solução da pressão de segunda ordem no espaço. Para melhorar a advecção em regiões próximas às bordas irregulares, introduzimos um método de interpolação que funciona em células poliédricas arbitrárias, utilizando-se do método de interpolação spherical barycentric coordinates (SBC). Essa abordagem possibilita que as linhas características do escoamento respeitem a geometria sem penetrá-la, em contraste com métodos tradicionais de interpolação lineares ou cúbicos. Finalmente, nós melhoramos os métodos de advecção com um método FLIP modificado. Nosso método resolve uma dificuldade inerente a advecção Semi-Lagrangiana no contexto de geometrias deslocando-se através do domínio de simulação: as células que são varridas por sólidos em locomoção perdem sua informação de velocidade e tem de ser preenchidas com velocidades extrapoladas de células vizinhas. Nosso esquema FLIP garante que a informação de velocidade viaje corretamente com as superfícies, não necessitando de nenhum método de extrapolação. / Fluid animation methods based on Eulerian grids have long struggled to resolve flows involving narrow gaps and thin solid features. Past approaches have artificially inflated or voxelized boundaries, although this sacrifices the correct geometry and topology of the fluid domain and prevents flow through narrow regions. We present a boundary-respecting fluid simulator that overcomes these challenges. Our solution is to intersect the solid boundary geometry with the cells of a background regular grid to generate a topologically correct, boundary-conforming cut-cell mesh. We extend both pressure projection and velocity advection to support this enhanced grid structure. For pressure projection, we introduce a general graph-based scheme that properly preserves discrete incompressibility even in thin and topologically complex flow regions, while nevertheless yielding symmetric positive definite linear systems. For advection, we exploit polyhedral interpolation to improve the degree to which the flow conforms to irregular and possibly non-convex cell boundaries, and propose a modified PIC/FLIP advection scheme to eliminate the need to inaccurately reinitialize invalid cells that are swept over by moving boundaries. The method naturally extends the standard Eulerian fluid simulation framework, and while we focus on thin boundaries, our contributions are beneficial for volumetric solids as well. Our results demonstrate successful one-way fluid-solid coupling in the presence of thin objects and narrow flow regions even on very coarse grids.

by Edward Nai Biu Tam. / Thesis (M.Phil.)--Chinese University of Hong Kong, 1996. / Includes bibliographical references (leaves 92-93). / Abstract --- p.ii / Acknowledgement --- p.iii / Chapter 1 --- Introduction --- p.1 / Chapter 1.1 --- Problems and Definitions --- p.1 / Chapter 1.1.1 --- Spatial Data --- p.1 / Chapter 1.1.2 --- Spatial Queries --- p.2 / Chapter 1.1.3 --- Spatial Access Method --- p.3 / Chapter 1.1.4 --- Motivations --- p.4 / Chapter 1.2 --- Architecture for Parallel SAM --- p.4 / Chapter 1.2.1 --- Parameters --- p.4 / Chapter 1.3 --- Objectives of the thesis --- p.7 / Chapter 1.4 --- Overview of the thesis --- p.7 / Chapter 2 --- Review of the Literature --- p.9 / Chapter 2.1 --- R-tree --- p.9 / Chapter 2.1.1 --- Structure --- p.9 / Chapter 2.1.2 --- Searching --- p.10 / Chapter 2.1.3 --- Searching Costs --- p.11 / Chapter 2.1.4 --- Insertion --- p.14 / Chapter 2.1.5 --- Deletion --- p.15 / Chapter 2.1.6 --- Splitting Algorithm --- p.16 / Chapter 2.2 --- Independent R-tree --- p.19 / Chapter 2.2.1 --- Data Distribution --- p.19 / Chapter 2.2.2 --- Space Partition --- p.19 / Chapter 2.3 --- Super Node --- p.19 / Chapter 2.4 --- Multiplexed R-tree --- p.20 / Chapter 2.4.1 --- Node Allocation Algorithm --- p.21 / Chapter 3 --- Comparison of Different Parallel R-tree Methods --- p.23 / Chapter 3.1 --- Throughput --- p.24 / Chapter 3.2 --- Service Time --- p.32 / Chapter 3.3 --- Summary --- p.37 / Chapter 3.3.1 --- Data Distribution --- p.37 / Chapter 3.3.2 --- Space Partition --- p.37 / Chapter 3.3.3 --- Multiplexed R-trees --- p.37 / Chapter 3.3.4 --- Super-nodes --- p.37 / Chapter 3.3.5 --- Conclusions --- p.38 / Chapter 4 --- Parallel Binary R-tree --- p.39 / Chapter 4.1 --- Architecture --- p.39 / Chapter 4.1.1 --- Extension of PBR-tree --- p.41 / Chapter 4.2 --- Searching Algorithm --- p.41 / Chapter 4.2.1 --- Asynchronous --- p.41 / Chapter 4.2.2 --- Synchronous --- p.45 / Chapter 4.3 --- Performance Evaluation --- p.45 / Chapter 4.3.1 --- Asynchronous --- p.49 / Chapter 4.3.2 --- Synchronous --- p.49 / Chapter 4.3.3 --- Comparison of the Cost models --- p.52 / Chapter 4.4 --- Application of PBR-tree --- p.54 / Chapter 4.4.1 --- Experimental Setup --- p.54 / Chapter 4.4.2 --- Experimental results --- p.55 / Chapter 4.5 --- Conclusions --- p.56 / Chapter 5 --- Multiplexed Parallel R-trees --- p.60 / Chapter 5.1 --- Architecture --- p.60 / Chapter 5.2 --- Searching --- p.61 / Chapter 5.3 --- Node Allocation Algorithm --- p.61 / Chapter 6 --- Comparisons and Experiment --- p.63 / Chapter 6.1 --- Assumptions and Experimental Setup --- p.63 / Chapter 6.2 --- Experimental Results --- p.65 / Chapter 6.2.1 --- Waiting time --- p.65 / Chapter 6.2.2 --- Service time --- p.65 / Chapter 6.3 --- Experimental results for large number of processors --- p.74 / Chapter 7 --- Conclusions --- p.83 / Chapter 7.1 --- Summary --- p.83 / Chapter 7.1.1 --- Studies on the previous works --- p.83 / Chapter 7.1.2 --- Parallel Binary R-tree --- p.84 / Chapter 7.1.3 --- Multiplexed Parallel R-trees --- p.84 / Chapter 7.2 --- Future Works --- p.84 / Chapter A --- Proximity Measure --- p.86 / Chapter B --- Summary of Variables and Symbols --- p.88 / Chapter C --- Proof of Equations --- p.90 / Bibliography --- p.92

by Song Zou. / Year shown on spine: 1997. / Thesis (M.Phil.)--Chinese University of Hong Kong, 1995. / Includes bibliographical references (leaves 69-[72]). / Chapter 1 --- Introduction --- p.1 / Chapter 2 --- Related works --- p.7 / Chapter 2.1 --- Spatial domain methods --- p.8 / Chapter 2.2 --- Transformation based methods --- p.9 / Chapter 2.3 --- Parallel Implement ation --- p.10 / Chapter 3 --- Parallel computation model --- p.12 / Chapter 3.1 --- Introduction --- p.12 / Chapter 3.2 --- Classifications of Parallel Computers --- p.13 / Chapter 3.3 --- The SIMD machine architectures --- p.15 / Chapter 3.4 --- The communication within the parallel processors --- p.16 / Chapter 3.5 --- The parallel display mechanisms --- p.17 / Chapter 4 --- Data preparation --- p.20 / Chapter 4.1 --- Introduction --- p.20 / Chapter 4.2 --- Original data layout in the processor array --- p.21 / Chapter 4.3 --- Shading --- p.21 / Chapter 4.4 --- Classification --- p.23 / Chapter 5 --- Fast data parallel rotation and resampling algorithms --- p.25 / Chapter 5.1 --- Introduction --- p.25 / Chapter 5.2 --- Affine Transformation --- p.26 / Chapter 5.3 --- Related works --- p.28 / Chapter 5.3.1 --- Resampling in ray tracing --- p.28 / Chapter 5.3.2 --- Direct Rotation --- p.28 / Chapter 5.3.3 --- General resampling approaches --- p.29 / Chapter 5.3.4 --- Rotation by shear --- p.29 / Chapter 5.4 --- The minimum mismatch rotation --- p.31 / Chapter 5.5 --- Load balancing --- p.33 / Chapter 5.6 --- Resampling algorithm --- p.35 / Chapter 5.6.1 --- Nearest neighbor --- p.36 / Chapter 5.6.2 --- Linear Interpolation --- p.36 / Chapter 5.6.3 --- Aitken's Algorithm --- p.38 / Chapter 5.6.4 --- Polynomial resampling in 3D --- p.40 / Chapter 5.7 --- A comparison between the resampling algorithms --- p.40 / Chapter 5.7.1 --- The quality --- p.42 / Chapter 5.7.2 --- Implement ation and cost --- p.44 / Chapter 6 --- Data reordering using binary swap --- p.47 / Chapter 6.1 --- The sorting algorithm --- p.48 / Chapter 6.2 --- The communication cost --- p.51 / Chapter 7 --- Ray composition --- p.53 / Chapter 7.1 --- Introduction --- p.53 / Chapter 7.2 --- Ray Composition by Monte Carlo Method --- p.54 / Chapter 7.3 --- The Associative Color Model --- p.56 / Chapter 7.4 --- Parallel Implementation --- p.60 / Chapter 7.5 --- Discussion and further improvement --- p.63 / Chapter 8 --- Conclusion and further work --- p.67 / Bibliography --- p.69

Lee Keung Tat. / Thesis (M.Phil.)--Chinese University of Hong Kong, 2003. / Includes bibliographical references (leaves 81-86). / Abstracts in English and Chinese. / Abstract --- p.i / Acknowledgments --- p.iii / Chapter 1 --- Introduction --- p.1 / Chapter 1.1 --- Motivation --- p.1 / Chapter 1.2 --- Contribution --- p.3 / Chapter 1.3 --- Previous Work --- p.5 / Chapter 1.4 --- Thesis Organization --- p.9 / Chapter 2 --- Overview --- p.10 / Chapter 3 --- Data Acquisition --- p.14 / Chapter 3.1 --- Acquiring the Surface Model --- p.14 / Chapter 3.2 --- Camera Calibration --- p.16 / Chapter 3.3 --- Capturing Image with Camera Pose --- p.18 / Chapter 3.3.1 --- Fastrack --- p.19 / Chapter 3.3.2 --- Tracking the Camera Pose --- p.21 / Chapter 3.3.3 --- Calibrating the Tracking System --- p.23 / Chapter 3.4 --- Summary --- p.32 / Chapter 4 --- Data Fusion --- p.33 / Chapter 4.1 --- Converting Surface Model to Point-Based Model --- p.33 / Chapter 4.2 --- Registering the Radiance Values onto the Point-Based Model --- p.36 / Chapter 4.3 --- Scattered Data Fitting --- p.40 / Chapter 4.3.1 --- Spherical Delaunay Triangulation --- p.41 / Chapter 4.3.2 --- Hierarchical Spherical Triangulation --- p.46 / Chapter 4.3.3 --- Interpolation --- p.49 / Chapter 4.4 --- Data Compression --- p.50 / Chapter 4.5 --- Summary --- p.52 / Chapter 5 --- Multiresolution Point-Based Representation and Rendering --- p.53 / Chapter 5.1 --- Multiresolution Point-Based Representation --- p.55 / Chapter 5.1.1 --- Construction --- p.57 / Chapter 5.2 --- Rendering --- p.62 / Chapter 5.2.1 --- Culling --- p.63 / Chapter 5.2.2 --- Drawing the Node --- p.66 / Chapter 5.3 --- Summary --- p.68 / Chapter 6 --- Experimental Results --- p.69 / Chapter 6.1 --- Tested Objects --- p.69 / Chapter 6.2 --- Evaluation --- p.70 / Chapter 6.3 --- Summary --- p.78 / Chapter 7 --- Conclusion --- p.79 / Chapter 7.1 --- Summary --- p.79 / Chapter 7.2 --- Future Direction --- p.80 / Bibliography --- p.81

Thesis (M.S.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 1981. / MICROFICHE COPY AVAILABLE IN ARCHIVES AND ENGINEERING. / Bibliography: leaf 72. / by Calvin McCoy Winey III. / M.S.

En informatique graphique, le rendu des matériaux occupe une place très importante dans la qualité de l’image finale. De nombreux modèles ont contribué à améliorer l’apparence des matériaux. Aujourd’hui, certains matériaux restent encore difficiles à représenter à cause de leur complexité. Parmi ceux ci,la famille des matériaux anisotropes reste peu étudiée et complexe. Dans cette thèse nous proposons une meilleure compréhension des matériaux anisotropes au travers d’un modèle pour les représenter ainsi qu’un outil permettant de mieux en contrôler l’apparence. Notre modèle de matériaux brossés ou rayés se base sur la simulation du transport lumineux au sein de la micro-géométrie d’une rayure pour restituer tous les détails en conservant des temps de rendus suffisamment courts pour rendre la scène de manière interactive.Notre outil d’édition des reflets anisotropes utilise le champ d’orientation des BRDF pour donner à l’utilisateur l’impression de dessiner ou de déformer des reflets directement sur l’objet. / In computer graphics, material appearance is a fundamental component of the final image quality. Many models have contributed to improve material appearance. Today, some materials remains hard to represent because of their complexity. Among them, anisotopic materials are especially complex and little studied. In this thesis, we propose a better comprehension of anisotropic materials providing a representation model and an editing tool to control their appearance. Our scratched material model is based on a light transport simulation in the micro-geometry of a scratch, preserves all the details and keeps an interactive rendering time. Our anisotropic reflections edition tool uses BRDF orientation fields to give the user the impression to draw or deform reflections directly on the surface.

With this work I wanted to examine how to improve readability of battlefields in top-down gamesfor VR by increasing the visual distinction between units. I analyzed three successful PC gameswithin the genre and created three different user tests to come up with my results and conclusions.The results from my VR test is compared to my non-VR tests to see what one has to do to reachthe same level of readability or better in VR. It turns out you need to put more time in to yourassets for improving readability in VR than without VR on a non-stereo display.