Un problème d'illumination inverse appliqué aux tunnels routiers

Ce rapport décrit ume méthode de recherche des meilleures configurations dans les tunnels routiers satisfaisant à une contrainte de niveaux d'éclaireme- nts suffisants. L'objectif est d'être capable, en partant des niveaux d'éclairements requis sur la chausseé, de remonter aux caractéristiques des sources, des murs, de la chaussée les plus appropriées, ainsi que de déterminer le nombre de sourcesàutiliser et leurs placements dans le tunnel. Il s'agit donc conceptuellement d'un problème de simulation inverse dépendant de nombreux paramètres que nous avons traité de façon originale afin de rendre sa complexité raisonnable. L'obtention de la courbe de luminances minimales est basée sur la notion de contraste et de perception visuelle des objets tout en tenant compte des phénomènes d'éblouissements que subit un automobilisteàl'approche du tunnel (on pourra consulter la thèse [13] partie 3). Le logiciel développé permet d'obtenir la configuration de tunnel optimale par rapport à la définition d'une certaine fonction coût (par exemple de coût de revient minimal) et satisfaisant aux contraintes de niveaux requi

Automatisation de la Méthode de Tour Into The Picture

La méthode de Tour Into the Picture (TIP) est une technique de rendu basé image. Son principe consiste à convertir une seule image en un ensemble de 5 polygones de coordonnées exprimées dans un repère 3D. A chacun de ces polygones est associée une texture représentant une partie de l'image redressée. Ensuite il est facile de naviguer dans la scène représentée par ces 5 polygones. Cette approche a deux inconvénients majeurs : le premier est l'obligation de régler un grand nombre de paramètres manuellement, le deuxième est l'ensemble de restrictions concernant la prise de vue originale (position et orientation). La méthode que nous proposons réduit au minimum les interventions de l'utilisateur et permet un maximum de liberté pour la prise de vue ; nous avons nommé cette méthode Automatic Tour Into the Picture (ATIP). Nous proposons aussi des méthodes efficaces pour extraire des lignes et points de fuite nécessaires à l'étalonnage de caméra à partir d'une seule image

Multiview Autostereoscopic Displays

This report describes the different technologies used par the manufacturers of autostereoscopic displays which are also called 3D displays. It also presents some existing 3D displays as well as the problems of resampling inherent in this kind of display. Next, it introduces more particularly the NEWSIGHT 3D displays as well as the interleaving of 8 views used by this kind of 3D display. The implementation of this interleaving on the CPU and on the GPU (programmable graphic cards) is also described

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Foreword to the special section on recent advances in graphics and interaction

This special section on Recent Advances in Graphics and In- teraction features the papers submitted to Computers & Graphics (C&G) and presented at the 2021 edition of the International Conference on Graphics and Interaction – ICGI’2021 – which was held on November 4 and 5, 2021 at the Faculty of Engineering of the University of Porto, Portugal, as a joint organization with the Eurographics Portuguese Chapter — GPCG.FCT -Fundação para a Ciência e a Tecnologia(undefined

A directional occlusion shading model for interactive direct volume rendering

Volumetric rendering is widely used to examine 3D scalar fields from CT/MRI scanners and numerical simulation datasets. One key aspect of volumetric rendering is the ability to provide perceptual cues to aid in understanding structure contained in the data. While shading models that reproduce natural lighting conditions have been shown to better convey depth information and spatial relationships, they traditionally require considerable (pre)computation. In this paper, a shading model for interactive direct volume rendering is proposed that provides perceptual cues similar to those of ambient occlusion, for both solid and transparent surface-like features. An image space occlusion factor is derived from the radiative transport equation based on a specialized phase function. The method does not rely on any precomputation and thus allows for interactive explorations of volumetric data sets via on-the-fly editing of the shading model parameters or (multi-dimensional) transfer functions while modifications to the volume via clipping planes are incorporated into the resulting occlusion-based shading

A Progressive Algorithm For Three Point Transport

When computing global illumination in environments made up of surfaces with general Bidirectionnal Reflection Distribution Function, a three point formulation of the rendering equation can be used. Brute-force algorithms can lead to a linear system of equations whose matrix is cubic, which is expensive in time and space. The hierarchical approach is more efficient. Aupperle et al. proposed a hierchical three point algorithm to compute global illumination in presence of glossy reflection. We present in this paper some improvements we brought to this method: shooting, "lazy" push-pull, photometric subdivision criterion... Then we will show how our new method takes into account non-planar surfaces in the hierarchical resolution process

A spherical gaussian framework for bayesian Monte Carlo rendering of glossy surfaces

The Monte Carlo method has proved to be very powerful to cope with global illumination problems but it remains costly in terms of sampling operations. In various applications, previous work has shown that Bayesian Monte Carlo can significantly outperform importance sampling Monte Carlo thanks to a more effective use of the prior knowledge and of the information brought by the samples set. These good results have been confirmed in the context of global illumination but strictly limited to the perfect diffuse case. Our main goal in this paper is to propose a more general Bayesian Monte Carlo solution that allows dealing with non-diffuse BRDFs thanks to a spherical Gaussian-based framework. We also propose a fast hyperparameters determination method which avoids learning the hyperparameters for each BRDF. These contributions represent two major steps towards generalizing Bayesian Monte Carlo for global illumination rendering. We show that we achieve substantial quality improvements over importance sampling at comparable computational cost.Fundação para a Ciência e a Tecnologia (FCT) within project PEst-OE/EEI/UI0752/201

Contrôle de caméra virtuelle à base de partitions spatiales dynamiques

Le contrôle de caméra virtuelle est aujourd'hui un composant essentiel dans beaucoup d'applications d'infographie. Malgré cette importance, les approches actuelles restent limitées en terme d'expressivité, d'interactivité et de performances. Typiquement, les éléments de style ou de genre cinématographique sont difficiles à modéliser et à simuler dû à l'incapacité des systèmes actuels de calculer simultanément des points de vues, des trajectoires et d'effectuer le montage. Deuxièmement, elles n'explorent pas assez le potentiel créatif offert par le couplage potentiel d'un humain et d'un système intelligent pour assister les utilisateurs dans une tâche complexe de construction de séquences cinématographiques. Enfin, la plupart des approches existantes se basent sur des techniques d'optimisation dans un espace de recherche 6D, qui s'avèrent coûteuses et donc inadaptées à un contexte interactif. Dans cette thèse, nous proposons tout d'abord un cadre unique intégrant les quatre aspects clés de la cinématographie (le calcul de point de vue, la planification de trajectoires, le montage et la visibilité). Ce cadre expressif permet de simuler certaines dimensions de style cinématographique. Nous proposons ensuite une méthodologie permettant de combiner les capacités d'un système automatique avec une interaction utilisateur. Enfin, nous présentons un modèle de contrôle de caméra efficace qui réduit l'espace de recherche de 6D à 3D. Ce modèle a le potentiel pour remplacer un certain nombre de formulations existantes.Virtual camera control is nowadays an essential component in many computer graphics applications. Despite its importance, current approaches remain limited in their expressiveness, interactive nature and performances. Typically, elements of directorial style and genre cannot be easily modeled nor simulated due to the lack of simultaneous control in viewpoint computation, camera path planning and editing. Second, there is a lack in exploring the creative potential behind the coupling of a human with an intelligent system to assist users in the complex task of designing cinematographic sequences. Finally, most techniques are based on computationally expensive optimization techniques performed in a 6D search space, which prevents their application to real-time contexts. In this thesis, we first propose a unifying approach which handles four key aspects of cinematography (viewpoint computation, camera path planning, editing and visibility computation) in an expressive model which accounts for some elements of directorial style. We then propose a workflow allowing to combine automated intelligence with user interaction. We finally present a novel and efficient approach to virtual camera control which reduces the search space from 6D to 3D and has the potential to replace a number of existing formulations.RENNES1-Bibl. électronique (352382106) / SudocSudocFranceF

Tone mapping HDR panoramas for viewing in Head Mounted Displays

Head-mounted displays enable a user to view a complete environment as if he/she was there; providing an immersive experience. However, the lighting in a full environment can vary significantly. Panoramic images captured with conventional, Low Dynamic Range (LDR), imaging of scenes with a large range of lighting conditions, can include areas of under- or over-exposed pixels. High Dynamic Range (HDR) imaging, on the other hand, is able to capture the full range of detail in a scene. However, HMDs are not currently HDR and thus the HDR panorama needs to be tone mapped before it can be displayed on the LDR HMD. While a large number of tone mapping operators have been proposed in the last 25 years, these were not designed for panoramic images, or for use with HMDs. This paper undertakes a two part subjective study to investigate which of the current, state-of-the-art tone mappers is most suitable for use with HMD