En synthèse d'images, le principal calcul à effectuer pour générer une image a été formalisé dans une équation appelée équation du rendu [Kajiya1986]. Cette équation est la intègre la conservation de l'énergie dans le transport de la lumière. Elle stipule que l'énergie lumineuse renvoyée, par les objets d'une scène, dans une direction donnée est égale à la somme de l'énergie émise et réfléchie par ceux-ci. De plus, l'énergie réfléchie par un élément de surface est définie comme la convolution de l'éclairement incident avec une fonction de réflectance. Cette dernière modélise le matériau (au sens physique) de l'objet et joue le rôle d'un filtre directionnel et énergétique dans l'équation du rendu, simulant ainsi la manière dont la surface se comporte vis-à-vis d'une réflexion. Dans ce mémoire de thèse, nous introduisons de nouvelles représentations pour la fonction de réflectance ainsi que pour la représentation de l'éclairement incident. Dans la première partie de ce mémoire, nous proposons deux nouveaux modèles pour représenter la fonction de réflectance. Le premier modèle s'inscrit dans une démarche artistique et est destiné à faciliter la création et l'édition des reflets spéculaires. Son principe est de laisser l'utilisateur peindre et esquisser les caractéristiques (forme, couleur, gradient et texture) du reflet spéculaire dans un plan de dessin paramétrisé en fonction de la direction de la réflexion miroir de la lumière. Le but du second modèle est de représenter de manière compacte et efficace les mesures des matériaux isotropes. Pour ce faire, nous introduisons une nouvelle représentation à base de polynômes rationnels. Les coefficients de ces derniers sont obtenus à l'aide d'un processus d'approximation qui garantit une solution optimale au sens de la convergence. Dans la seconde partie de ce mémoire, nous introduisons une nouvelle représentation volumétrique pour l'éclairement indirect représenté directionnellement à l'aide de vecteurs d'irradiance. Nous montrons que notre représentation est compacte et robuste aux variations géométriques et qu'elle peut être utilisée comme système de cache pour du rendu temps réel ou non, ainsi que dans le cadre de la transmission progressive des données (\textit{streaming}). Enfin, nous proposons deux types de modifications de l'éclairement incident afin de mettre en valeur les détails et les formes d'une surface. Le première modification consiste à perturber les directions de l'éclairement incident tandis que la seconde consiste à en modifier l'intensité. / In image synthesis, the main computation involved to generate an image is characterized by an equation named rendering equation [Kajiya1986]. This equation represents the law of energy conservation. It stipulates that the light emanating from the scene objects is the sum of the emitted energy and the reflected energy. Moreover, the reflected energy at a surface point is defined as the convolution of the incoming lighting with a reflectance function. The reflectance function models the object material and represents, in the rendering equation, a directional and energetic filter that describes the surface behavior regarding the reflection. In this thesis, we introduce new representations for the reflectance function and the incoming lighting. In the first part of this thesis, we propose two new models for the reflectance function. The first model is targeted for artists to help them create and edit highlights. Our main idea is to let the user paint and sketch highlight characteristics (shape, color, gradient and texture) in a plane parametrized by the incident lighting direction. The second model is designed to represent efficiently isotropic material data. To achieve this result, we introduce a new representation of the reflectance function that uses rational polynomials. Their coefficients are computed using a fitting process that guarantees an optimal solution regarding convergence. In the second part of this thesis, we introduce a new volumetric structure for indirect illumination that is directionally represented with irradiance vector. We show that our representation is compact and robust to geometric variations, that it can be used as caching system for interactive and offline rendering and that it can also be transmitted with streaming techniques. Finally, we introduce two modifications of the incoming lighting to improve the shape depiction of a surface. The first modification consists in warping the incoming light directions whereas the second one consists in scaling the intensity of each light source.

Cette thèse introduit un cadre théorique pour l'étude de différents schémas d'échantillonnage dans un domaine sphérique, et de leurs effets sur le calcul d'intégrales pour l'illumination globale. Le calcul de l'illumination (du transport lumineux) est un composant majeur de la synthèse d'images réalistes, qui se traduit par l'évaluation d'intégrales multidimensionnelles. Les schémas d'intégration numériques de type Monte-Carlo sont utilisés intensivement pour le calcul de telles intégrales. L'un des aspects majeurs de tout schéma d'intégration numérique est l'échantillonnage. En effet, la façon dont les échantillons sont distribués dans le domaine d'intégration peut fortement affecter le résultat final. Par exemple, pour la synthèse d'images, les effets liés aux différents schémas d'échantillonnage apparaissent sous la forme d'artéfacts structurés ou, au contrire, de bruit non structuré. Dans de nombreuses situations, des résultats complètement faux (biaisés) peuvent être obtenus à cause du schéma d'échantillonnage utilisé pour réaliser l'intégration. La distribution d'un échantillonnage peut être caractérisée à l'aide de son spectre de Fourier. Des schémas d'échantillonnage peuvent être générés à partir d'un spectre de puissance dans le domaine de Fourier. Cette technique peut être utilisée pour améliorer l'erreur d'intégration, car un tel contrôle spectral permet d'adapter le schéma d'échantillonnage au spectre de Fourier de l'intégrande. Il n'existe cependant pas de relation directe entre l'erreur dans l'intégration par méthode de Monte-Carlo et le spectre de puissance de la distribution des échantillons. Dans ces travaux, nous proposons une formulation de la variance qui établit un lien direct entre la variance d'une méthode de Monte-Carlo, les spectres de puissance du schéma d'échantillonnage ainsi que de l'intégrande. Pour obtenir notre formulation de la variance, nous utilisons la notion d'homogénéité de la distribution des échantillons qui permet d'exprimer l'erreur de l'intégration par une méthode de Monte-Carlo uniquement sous forme de variance. À partir de cette formulation de la variance, nous développons un outil d'analyse pouvant être utilisé pour déterminer le taux de convergence théorique de la variance de différents schémas d'échantillonnage proposés dans la littérature. Notre analyse fournit un éclairage sur les bonnes pratiques à mettre en œuvre dans la définition de nouveaux schémas d'échantillonnage basés sur l'intégrande / This dissertation introduces a theoretical framework to study different sampling patterns in the spherical domain and their effects in the evaluation of global illumination integrals. Evaluating illumination (light transport) is one of the most essential aspect in image synthesis to achieve realism which involves solving multi-dimensional space integrals. Monte Carlo based numerical integration schemes are heavily employed to solve these high dimensional integrals. One of the most important aspect of any numerical integration method is sampling. The way samples are distributed on an integration domain can greatly affect the final result. For example, in images, the effects of various sampling patterns appear in the form of either structural artifacts or completely unstructured noise. In many cases, we may get completely false (biased) results due to the sampling pattern used in integration. The distribution of sampling patterns can be characterized using their Fourier power spectra. It is also possible to use the Fourier power spectrum as input, to generate the corresponding sample distribution. This further allows spectral control over the sample distributions. Since this spectral control allows tailoring new sampling patterns directly from the input Fourier power spectrum, it can be used to improve error in integration. However, a direct relation between the error in Monte Carlo integration and the sampling power spectrum is missing. In this work, we propose a variance formulation, that establishes a direct link between the variance in Monte Carlo integration and the power spectra of both the sampling pattern and the integrand involved. To derive our closed-form variance formulation, we use the notion of homogeneous sample distributions that allows expression of error in Monte Carlo integration, only in the form of variance. Based on our variance formulation, we develop an analysis tool that can be used to derive theoretical variance convergence rates of various state-of-the-art sampling patterns. Our analysis gives insights to design principles that can be used to tailor new sampling patterns based on the integrand

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.

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.

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.