A iluminação indireta é capaz de elevar consideravelmente a qualidade visual de cenas renderizadas, mas é também uma operação custosa. Por este motivo, há muito esforço de pesquisa voltado para a renderização de iluminação indireta em tempo real. Apesar de atualmente existirem técnicas poderosas para a iluminação indireta em tempo real, elas fornecem ao artista apenas um controle grosseiro do equilíbrio entre qualidade e desempenho. Nós propomos uma Malha de Luzes Virtuais para calcular a iluminação indireta difusa numa cena, inspirados pelo uso de outras malhas auxiliares, como Malhas de Navegação e Malhas de Colisão. Uma Malha de Luzes Virtuais (MLV) é uma malha simplificada de luzes poligonais usadas para aproximar a luz refletida pela geometria real. Juntamente com a MLV, nós projetamos uma estrutura de dados de aceleração para atingir um desempenho eficiente com iluminação indireta usando uma MLV complexa. O uso da MLV apresenta algumas características vantajosas: maior controle artístico dos atributos da iluminação indireta; a possibilidade de integração com técnicas existentes como animação esquelética e geração procedural; e integração simples com ferramentas e processos de produção de arte existentes. Nossos resultados experimentais mostram que a iluminação indireta controlada por artistas é uma alternativa viável a métodos existentes. / Indirect illumination on a rendered scene can add a great deal to its visual quality, but it is also a costly operation. Therefore, a lot of research targets how to render indirect illumination in real-time. While powerful techniques for real-time indirect illumination currently exist, they provide only coarse-grained artistic control over the trade-off between quality and speed. We propose a Virtual Light Mesh to compute the scene’s diffuse indirect illumination, inspired by the use of other current auxiliary meshes such as Navigation Meshes and Collision Meshes. A Virtual Light Mesh (VLM) is a simplified mesh of polygonal lights used to approximate the light bounced by the real geometry. Together with the VLM, we design an acceleration data structure for efficient indirect illumination performance with a complex VLM. The use of VLM presents some positive properties: greater artistic control of the indirect illumination characteristics; the possibility of integration with existing techniques such as skeletal animation and procedural generation; and simple integration into existing asset production tools and pipelines. Our experimental results show that artist controlled indirect illumination is a viable alternative to existing methods.

Produzir imagens de alta qualidade por computador, no menor tempo possível, que sejam convincentes ao público alvo, utilizando-se de maneira ótima todos os recursos computacionais à disposição, é uma tarefa que envolve uma cadeia de processos específicos, sendo um grande desafio ainda nos dias de hoje. O presente trabalho apresenta um estudo sobre toda esta cadeia de processos, com foco na avaliação de métodos de Iluminação Global empregados na Síntese de Imagens fotorrealistas para as áreas de Animação e Efeitos Visuais. Com o objetivo de auxiliar o usuário na tarefa de produzir imagens fotorrealistas de alta qualidade, foram realizados experimentos envolvendo diversas cenas de teste e seis métodos de Iluminação Global do Estado da Arte: Path Tracing, Light Tracing, Bidirectional Path Tracing, Metropolis Light Transport, Progressive Photon Mapping e Vertex Connection and Merging. O sintetizador escolhido para execução do experimento foi o Mitsuba Renderer. Para avaliação da qualidade dos resultados, duas métricas perceptuais foram adotadas: o Índice de Similaridade Estrutural SSIM e o Previsor de Diferenças Visuais HDR-VDP-2. A partir da avaliação dos resultados, foi construído um Guia de Recomendações para o usuário, indicando, com base nas características de uma cena arbitrária, o método de Iluminação Global mais adequado para realizar a síntese das imagens. Por fim, foram apontados caminhos de pesquisa para trabalhos futuros, sugerindo o emprego de classificadores, métodos de redução de parâmetros e Inteligência Artificial a fim de automatizar o processo de produção de imagens fotorrealistas e de alta qualidade. / The task of generating high quality computer images in the shortest time possible, believable to the targets audience perception, using all computational resources available, is still a challenging procedure, composed by a chain of specific processes. This work presents a study of this chain, focusing on the evaluation of Global Illumination methods used on the Synthesis of Photorealistic Images, in the areas of Animation and Visual Effects. To achieve the goal of helping users to produce high-quality photorealistic images, two experiments were proposed containing several test scenes and six State-of-the-Art Global Illumination methods: Path Tracing, Light Tracing, Bidirectional Path Tracing, Metropolis Light Transport, Progressive Photon Mapping and Vertex Connection and Merging. In order to execute the tests, the open source renderer Mitsuba was used. The quality of the produced images was analyzed using two different perceptual metrics: Structural Similarity Index SSIM and Visual Difference Predictor HDR-VDP-2. By analyzing results, a Recommendation Guide was created, providing suggestions, based on an arbitrary scenes characteristics, of the most suitable Global Illumination method to be used in order to synthesize images from the given scene. In the end, future ways of research are presented, proposing the use of classifiers, parameter reduction methods and Artificial Intelligence, in order to build an automatic procedure to generate high quality photorealistic images.

Global illumination is an important factor when striving for photo realism in computergraphics. This thesis describes why this is the case, and why global illumination is considered acomplex problem to solve. The problem becomes even more demanding when considering realtime purposes. Resent research has proven it possible to produce global illumination in realtime. Therefore the subject of this thesis is to compare and evaluate a number of those methods. An implementation is presented based on the Imperfect shadow maps method, which per se isbased on instant radiosity and reflective shadow maps. The implementation is able to renderplausible global illumination effects in real time, for fully dynamic scenes. With conclusions that while it demonstrably is possible to provide believable global illum-ination in real time, it is not without shortcomings. In every case approximations or restrictionshas to be done to some extent, sometimes leading to wrong results. Though in most cases, notvisually unpleasing by a great deal. The final conclusion is that global illumination is possible on current hardware, with believablequality and good speed. Showing great potential for future implementations on next generationof hardware.

A iluminação indireta é capaz de elevar consideravelmente a qualidade visual de cenas renderizadas, mas é também uma operação custosa. Por este motivo, há muito esforço de pesquisa voltado para a renderização de iluminação indireta em tempo real. Apesar de atualmente existirem técnicas poderosas para a iluminação indireta em tempo real, elas fornecem ao artista apenas um controle grosseiro do equilíbrio entre qualidade e desempenho. Nós propomos uma Malha de Luzes Virtuais para calcular a iluminação indireta difusa numa cena, inspirados pelo uso de outras malhas auxiliares, como Malhas de Navegação e Malhas de Colisão. Uma Malha de Luzes Virtuais (MLV) é uma malha simplificada de luzes poligonais usadas para aproximar a luz refletida pela geometria real. Juntamente com a MLV, nós projetamos uma estrutura de dados de aceleração para atingir um desempenho eficiente com iluminação indireta usando uma MLV complexa. O uso da MLV apresenta algumas características vantajosas: maior controle artístico dos atributos da iluminação indireta; a possibilidade de integração com técnicas existentes como animação esquelética e geração procedural; e integração simples com ferramentas e processos de produção de arte existentes. Nossos resultados experimentais mostram que a iluminação indireta controlada por artistas é uma alternativa viável a métodos existentes. / Indirect illumination on a rendered scene can add a great deal to its visual quality, but it is also a costly operation. Therefore, a lot of research targets how to render indirect illumination in real-time. While powerful techniques for real-time indirect illumination currently exist, they provide only coarse-grained artistic control over the trade-off between quality and speed. We propose a Virtual Light Mesh to compute the scene’s diffuse indirect illumination, inspired by the use of other current auxiliary meshes such as Navigation Meshes and Collision Meshes. A Virtual Light Mesh (VLM) is a simplified mesh of polygonal lights used to approximate the light bounced by the real geometry. Together with the VLM, we design an acceleration data structure for efficient indirect illumination performance with a complex VLM. The use of VLM presents some positive properties: greater artistic control of the indirect illumination characteristics; the possibility of integration with existing techniques such as skeletal animation and procedural generation; and simple integration into existing asset production tools and pipelines. Our experimental results show that artist controlled indirect illumination is a viable alternative to existing methods.

A iluminação indireta é capaz de elevar consideravelmente a qualidade visual de cenas renderizadas, mas é também uma operação custosa. Por este motivo, há muito esforço de pesquisa voltado para a renderização de iluminação indireta em tempo real. Apesar de atualmente existirem técnicas poderosas para a iluminação indireta em tempo real, elas fornecem ao artista apenas um controle grosseiro do equilíbrio entre qualidade e desempenho. Nós propomos uma Malha de Luzes Virtuais para calcular a iluminação indireta difusa numa cena, inspirados pelo uso de outras malhas auxiliares, como Malhas de Navegação e Malhas de Colisão. Uma Malha de Luzes Virtuais (MLV) é uma malha simplificada de luzes poligonais usadas para aproximar a luz refletida pela geometria real. Juntamente com a MLV, nós projetamos uma estrutura de dados de aceleração para atingir um desempenho eficiente com iluminação indireta usando uma MLV complexa. O uso da MLV apresenta algumas características vantajosas: maior controle artístico dos atributos da iluminação indireta; a possibilidade de integração com técnicas existentes como animação esquelética e geração procedural; e integração simples com ferramentas e processos de produção de arte existentes. Nossos resultados experimentais mostram que a iluminação indireta controlada por artistas é uma alternativa viável a métodos existentes. / Indirect illumination on a rendered scene can add a great deal to its visual quality, but it is also a costly operation. Therefore, a lot of research targets how to render indirect illumination in real-time. While powerful techniques for real-time indirect illumination currently exist, they provide only coarse-grained artistic control over the trade-off between quality and speed. We propose a Virtual Light Mesh to compute the scene’s diffuse indirect illumination, inspired by the use of other current auxiliary meshes such as Navigation Meshes and Collision Meshes. A Virtual Light Mesh (VLM) is a simplified mesh of polygonal lights used to approximate the light bounced by the real geometry. Together with the VLM, we design an acceleration data structure for efficient indirect illumination performance with a complex VLM. The use of VLM presents some positive properties: greater artistic control of the indirect illumination characteristics; the possibility of integration with existing techniques such as skeletal animation and procedural generation; and simple integration into existing asset production tools and pipelines. Our experimental results show that artist controlled indirect illumination is a viable alternative to existing methods.

In computer graphics, lighting is an important area. To simulate shadows from area light sources, indirect lighting and shadows from indirect light, a class of algorithms commonly known as global illumination algorithms can be used. Ambient occlusion is an approximation to global illumination that can emulate shadows from area light sources and shadows from indirect light, giving very soft shadows. For real-time applications, ambient occlusion can be precomputed and stored in maps or per vertex. However, that can only be done with good results if the geometry is static. Therefore, a number of methods that can handle more or less dynamic scenes have been introduced in the recent years. In this thesis, a collection of ambient occlusion methods for dynamic objects and procedural environments will be described. The main contribution is the introduction of a novel method that handles ambient occlusion for procedural environments. Another contribution is a description of an implementation of Screen Space Ambient Occlusion (SSAO). SSAO is an algorithm that calculates approximate ambient occlusion in real-time by using the depths of surrounding pixels. It handles completely dynamic scenes with good performance. The method for procedural environments handles the scenario where a number of building blocks are procedurally assembled at run-time. The idea is to precompute an ambient occlusion map for each building block where the self-occlusion is stored. In addition, an ambient occlusion grid is precomputed for each block to accommodate the inter-block occlusion. At run-time, after the building blocks have been assembled, the ambient occlusion from the grids is blended with the ambient occlusion from the maps to generate new maps, valid for the procedural environment. Following that, the environment can be rendered with high quality ambient occlusion at almost no cost, in the same fashion as for a static environment where the ambient occlusion maps can be completely precomputed.

This thesis explores Voxel Cone Tracing as a possible Global Illumination solutionon mobile devices.The rapid increase of performance on low-power graphics processors hasmade a big impact. More advanced computer graphics algorithms are now possi-ble on a new range of devices. One category of such algorithms is Global Illumi-nation, which calculates realistic lighting in rendered scenes. The combinationof advanced graphics and portability is of special interest to implement in newtechnologies like Virtual Reality.The result of this thesis shows that while possible to implement a state of theart Global Illumination algorithm, the performance of mobile Graphics Process-ing Units is still not enough to make it usable in real-time.

La simulation d'éclairage est un processus qui s'avère plus complexe (temps de calcul, coût mémoire, mise en œuvre complexe) aussi bien pour les matériaux brillants que pour les matériaux lambertiens ou spéculaires. Afin d'éviter le calcul coûteux de certains termes de l'équation de luminance (convolution entre la fonction de réflexion des matériaux et la distribution de luminance de l'environnement), nous proposons une nouvelle structure de données appelée Source Surfacique Équivalente (SSE). L'utilisation de cette structure de données nécessite le pré-calcul puis la modélisation du comportement des matériaux soumis à divers types de sources lumineuses (positions, étendues). L'exploitation d'algorithmes génétiques nous permet de déterminer les paramètres des modèles de BRDF, en introduisant une première source d'approximation. L'approche de simulation d'éclairage utilisée est basée sur un cache de luminance. Ce dernier consiste à stocker l'éclairement incident sous forme de SSE en des points appelés enregistrements. Durant la simulation d'éclairage, l'environnement lumineux doit également être assimilé à un ensemble de sources surfaciques équivalentes (en chaque enregistrement) qu'il convient de définir de manière dynamique. Cette phase constitue une deuxième source d'erreur. Toutefois, l'incertitude globale ne se réduit pas au cumul des approximations réalisées à chaque étape. Les comparatives réalisées prouvent, au contraire, que l'approche des Sources Surfaciques Équivalentes est particulièrement intéressante pour des matériaux rugueux ou pour les matériaux très brillants placés dans des environnements relativement uniformes. L'utilisation de SSE a permis de réduire considérablement à la fois le coût mémoire et le temps de calcul. Une fois que les SSE sont calculés en chaque enregistrement et pour un certain nombre de points de vue, nous proposons une nouvelle méthode de visualisation interactive exploitant les performances des GPU (carte graphique) et s'avérant plus rapide que les méthodes existantes. Enfin nous traiterons le cas où les grandeurs photométriques sont spectrales, ce qui est très important lorsqu'il s'agit de réaliser des simulations d'éclairage précises. Nous montrerons comment adapter les zones d'influence des enregistrements en fonction des gradients de luminance et de la géométrie autour des enregistrements. / Radiance caching methods have proven efficient for global illumination. Their goal is to compute precisely illumination values (incident radiance or irradiance) at a reasonable number of points lying on the scene surfaces. These points, called records, are stored in a cache used for estimating illumination of other points in the scene. Unfortunately, with records lying on glossy surfaces, the irradiance value alone is not sufficient to evaluate the reflected radiance; each record should also store the incident radiance for all incident directions. Memory storage can be reduced with projection techniques using spherical harmonics or other basis functions. These techniques provide good results with low shininess BRDFs. However, they get impractical for shininess of even moderate value since the number of projection coefficients increase drastically. In this paper, we propose a new radiance caching method, that handles highly glossy surfaces, while requiring a low memory storage. Each cache record stores a coarse representation of the incident illumination thanks to a new data structure called Equivalent Area light Sources (EAS), capable of handling fuzzy mirror surfaces. In addition, our method proposes a new simplification of the interpolation process since it avoids the need for expressing and evaluating complex gradients. Moreover, we propose a new GPU based visualisation method which exploits these EAS data structure. Thus, interactive rendering is done faster than existing methods. Finally, physical ligting simulations need to manipulate spectral physical quantities. We demonstrate in our work how these quantities can be handle with our technic by adapting the record influence zone depending on the radiance gradients and the geometry around the records.

This thesis deals with problem of computation of global illumination in real-time. Two methods are described. Namely Reflective Shadow Maps and Light Propagation Volumes. The first of them deals with the problem by using extended Shadow Mapping algorithm. The second one uses scene embedded into a 3D grid together with Spherical harmonics to compute light propagation in the scene. Furthermore this thesis contains results of measurement of the rendering speed of the Light Propagation Volumes algorithm with various settings on several machines. Quality of the resulting output of the algorithm is also evaluated.

This thesis deals with the estimation of global illumination of a~scene. Global illumination is expressed as a~physical simulation in connection with illumination methods used in current computer graphics. In the practical part there is expressed an implementation of global illumination estimation using photon maps.