Algorithms are presented that enable the use of vector graphics representations of images in texture maps for 3D real time rendering. Vector graphics images are resolution independent and can be zoomed arbitrarily without losing detail or crispness. Many important types of images, including text and other symbolic information, are best represented in vector form. Vector graphics textures can also be used as transparency mattes to augment geometric detail in models via trim curves. Spline curves are used to represent boundaries around regions in standard vector graphics representations, such as PDF and SVG. Antialiased rendering of such content can be obtained by thresholding implicit representations of these curves. The distance function is an especially useful implicit representation. Accurate distance function computations would also allow the implementation of special effects such as embossing. Unfortunately, computing the true distance to higher order spline curves is too expensive for real time rendering. Therefore, normally either the distance is approximated by normalizing some other implicit representation or the spline curves are approximated with simpler primitives. In this thesis, three methods for rendering vector graphics textures in real time are introduced, based on various approximations of the distance computation. The first and simplest approach to the distance computation approximates curves with line segments. Unfortunately, approximation with line segments gives only C0 continuity. In order to improve smoothness, spline curves can also be approximated with circular arcs. This approximation has C1 continuity and computing the distance to a circular arc is only slightly more expensive than computing the distance to a line segment. Finally an iterative algorithm is discussed that has good performance in practice and can compute the distance to any parametrically differentiable curve (including polynomial splines of any order) robustly. This algorithm is demonstrated in the context of a system capable of real-time rendering of SVG content in a texture map on a GPU. Data structures and acceleration algorithms in the context of massively parallel GPU architectures are also discussed. These data structures and acceleration structures allow arbitrary vector content (with space-variant complexity, and overlapping regions) to be represented in a random-access texture.

Algorithms are presented that enable the use of vector graphics representations of images in texture maps for 3D real time rendering. Vector graphics images are resolution independent and can be zoomed arbitrarily without losing detail or crispness. Many important types of images, including text and other symbolic information, are best represented in vector form. Vector graphics textures can also be used as transparency mattes to augment geometric detail in models via trim curves. Spline curves are used to represent boundaries around regions in standard vector graphics representations, such as PDF and SVG. Antialiased rendering of such content can be obtained by thresholding implicit representations of these curves. The distance function is an especially useful implicit representation. Accurate distance function computations would also allow the implementation of special effects such as embossing. Unfortunately, computing the true distance to higher order spline curves is too expensive for real time rendering. Therefore, normally either the distance is approximated by normalizing some other implicit representation or the spline curves are approximated with simpler primitives. In this thesis, three methods for rendering vector graphics textures in real time are introduced, based on various approximations of the distance computation. The first and simplest approach to the distance computation approximates curves with line segments. Unfortunately, approximation with line segments gives only C0 continuity. In order to improve smoothness, spline curves can also be approximated with circular arcs. This approximation has C1 continuity and computing the distance to a circular arc is only slightly more expensive than computing the distance to a line segment. Finally an iterative algorithm is discussed that has good performance in practice and can compute the distance to any parametrically differentiable curve (including polynomial splines of any order) robustly. This algorithm is demonstrated in the context of a system capable of real-time rendering of SVG content in a texture map on a GPU. Data structures and acceleration algorithms in the context of massively parallel GPU architectures are also discussed. These data structures and acceleration structures allow arbitrary vector content (with space-variant complexity, and overlapping regions) to be represented in a random-access texture.

This thesis describes two new techniques for enhancing the rendering quality of cartoon characters in toon-shading applications. The proposed methods can be used to improve the output quality of current cel shaders. The first technique which uses 2D image-based algorithms, enhances the silhouettes of the input geometry and reduces the computer generated artefacts. The silhouettes are found by using the Sobel filter and reconstructed by Bezier curve fitting. The intensity of the reconstructed silhouettes is then modified to create a stylised appearance. In the second technique, a new hair model based on billboarded particles is introduced. This method is found to be particularly useful for generating toon-like specular highlights for hair, which are important in cartoon animations. The whole rendering framework is implemented in C++ using the OpenGL API. OpenGL extensions and GPU programming are used to take the advantage of the functionalities of currently available graphics hardware. The programming of graphics hardware is done using Cg, a high level shader language.

[pt] A representação de formas é um problema fundamental em Computação Gráfica. Dentre as representações conhecidas para objetos tridimensionais, os campos de distância amostrados adaptativamente (ADFs) destacam-se por sua versatilidade. ADFs combinam os conceitos de geometria com dados volumétricos, permitem representar objetos com precisão arbitrária, e consolidam diversas operações como visualização, modelagem de níveis de detalhe, detecção de colisão, testes de proximidade, metamorfose e operações booleanas em uma única representação. Este trabalho propõe métodos para acelerar a reconstrução de ADFs estáticas, melhorar a qualidade dos campos reconstruídos, e visualizar iso-superfícies das ADFs, valendo-se do enorme poder computacional encontrado nas placas gráficas modernas (GPUs). Para que as ADFs sejam representadas de forma eficiente em placas gráficas, propõe-se o uso de uma estrutura hierárquica baseada em dispersão espacial perfeita. A renderização de ADFs é feita integralmente pela GPU, utilizando uma técnica de lançamento de raios baseada em traçado por esferas. Uma maneira de tratar as descontinuidades C0 e C1 inerentes às ADFs é sugerida para que o sombreamento das superfícies seja suave. Finalmente, o trabalho propõe um novo método de reconstrução para ADFs, capaz de representar melhor superfícies curvas. Os resultados são apresentados através de aplicações simples de visualização interativa, com ADFs geradas a partir de malhas de triângulos e sólidos primitivos. / [en] Shape representation is a fundamental problem in Computer Graphics. Among known representations for three-dimensional objects, adaptively sampled distance fields (ADFs) are noted for their versatility. ADFs combine the concepts of geometry with volume data, allow objects to be represented with arbitrary precision, and consolidate several operations - such as visualization, level-of-detail modeling, collision detection, proximity tests, morphing and boolean operations | into a single representation. This work proposes methods to accelerate the reconstruction of static ADFs, to improve the quality of reconstructed fields, and to visualize ADF isosurfaces, making use of the massive computational power found in modern graphics hardware (GPUs). In order to effciently represent ADFs on graphics cards, a hierarchical structure based on perfect spatial hashing is proposed. Rendering of ADFs is done completely on GPUs, using a ray casting technique based on sphere tracing. Means to overcome the C0 and C1 discontinuities inherent to ADFs are suggested in order to attain smoothly shaded iso-surfaces. Finally, a new reconstruction method for ADFs, which can better represent curved surfaces, is proposed. Results are presented through simple interactive visualization applications, with ADFs generated from both triangle meshes and primitive solids.

<p>Volume rendering techniques can be powerful tools when visualizing medical data sets. The characteristics of being able to capture 3-D internal structures make the technique attractive. Scanning equipment is producing medical images, with rapidly increasing resolution, resulting in heavily increased size of the data set. Despite the great amount of processing power CPUs deliver, the required precision in image quality can be hard to obtain in real-time rendering. Therefore, it is highly desirable to optimize the rendering process.</p><p>Modern GPUs possess much more computational power and is available for general purpose programming through high level shading languages. Efficient representations of the data are crucial due to the limited memory provided by the GPU. This thesis describes the theoretical background and the implementation of an approach presented by Patric Ljung, Claes Lundström and Anders Ynnerman at Linköping University. The main objective is to implement a fully working multi-resolution framework with two separate pipelines for pre-processing and real-time rendering, which uses the GPU to visualize large medical data sets.</p>

Volume rendering techniques can be powerful tools when visualizing medical data sets. The characteristics of being able to capture 3-D internal structures make the technique attractive. Scanning equipment is producing medical images, with rapidly increasing resolution, resulting in heavily increased size of the data set. Despite the great amount of processing power CPUs deliver, the required precision in image quality can be hard to obtain in real-time rendering. Therefore, it is highly desirable to optimize the rendering process. Modern GPUs possess much more computational power and is available for general purpose programming through high level shading languages. Efficient representations of the data are crucial due to the limited memory provided by the GPU. This thesis describes the theoretical background and the implementation of an approach presented by Patric Ljung, Claes Lundström and Anders Ynnerman at Linköping University. The main objective is to implement a fully working multi-resolution framework with two separate pipelines for pre-processing and real-time rendering, which uses the GPU to visualize large medical data sets.

In order to reduce the large execution time of an existing fingerprint enhancement system, a parallel implementation method based on GPU via CUDA is proposed. Firstly, the necessity and feasibility of employing parallel programming for the whole system are analyzed. Then pre-processing, global analysis, local analysis and matched filtering of the whole fingerprint enhancement system is designed, optimized and implemented respectively using parallel computing technology via CUDA. Finally, numerous fingerprints from FVC2000 databases are tested and the  obtained execution time is compared with that of the CPU based system. The results show that the execution time is significantly reduced by using the parallel implementation method based on GPU.

In this thesis, we address issues associated with programming modern heterogeneous systems while focusing on a special kind of heterogeneous systems that include multicore CPUs and one or more GPUs, called GPU-based systems.We consider the skeleton programming approach to achieve high level abstraction for efficient and portable programming of these GPU-based systemsand present our work on SkePU library which is a skeleton library for these systems. We extend the existing SkePU library with a two-dimensional (2D) data type and skeleton operations and implement several new applications using newly made skeletons. Furthermore, we consider the algorithmic choice present in SkePU and implement support to specify and automatically optimize the algorithmic choice for a skeleton call, on a given platform. To show how to achieve performance, we provide a case-study on optimized GPU-based skeleton implementation for 2D stencil computations and introduce two metrics to maximize resource utilization on a GPU. By devising a mechanism to automatically calculate these two metrics, performance can be retained while porting an application from one GPU architecture to another. Another contribution of this thesis is implementation of the runtime support for the SkePU skeleton library. This is achieved with the help of the StarPUruntime system. By this implementation,support for dynamic scheduling and load balancing for the SkePU skeleton programs is achieved. Furthermore, a capability to do hybrid executionby parallel execution on all available CPUs and GPUs in a system, even for a single skeleton invocation, is developed. SkePU initially supported only data-parallel skeletons. The first task-parallel skeleton (farm) in SkePU is implemented with support for performance-aware scheduling and hierarchical parallel execution by enabling all data parallel skeletons to be usable as tasks inside the farm construct. Experimental evaluations are carried out and presented for algorithmic selection, performance portability, dynamic scheduling and hybrid execution aspects of our work.

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