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Start date: 1988 × Author: Bouatouch, Kadi ×

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Now showing 1 - 10 of 27
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    EUROGRAPHICS 2016: Tutorials Frontmatter
    (Eurographics Association, 2016) Sousa, A. Augusto; Bouatouch, Kadi;
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    ATIP: A Tool for 3D Navigation inside a Single Image with Automatic Camera Calibration
    (The Eurographics Association, 2006) Boulanger, Kevin; Bouatouch, Kadi; Pattanaik, Sumanta; Louise M. Lever and Mary McDerby
    Automatic Tour Into the Picture (ATIP) is an extension of the Tour Into the Picture method [HAA97] that allows an approximative but visually convincing 3D walk-through inside a single image by rendering a box textured using the input image data. The original algorithm requires a long and tedious user interaction to determine the box dimensions and the perspective parameters, and imposes several constraints on the input image orientation. The goal of this paper is to present a framework providing fully automatic and fast camera calibration for any view orientation without using a calibration target. Our method reduces the user interaction, hence only a couple of seconds are required between the input image loading and the final walk-through.
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    Spatial Directional Radiance Caching
    (The Eurographics Association and Blackwell Publishing Ltd, 2009) Gassenbauer, Vaclav; Krivanek, Jaroslav; Bouatouch, Kadi
    We present a new approach for accelerated global illumination computation in scenes with glossy surfaces. Our algorithm combines sparse illumination computation used in the radiance caching algorithm with BRDF importance sampling. To make this approach feasible, we extend the idea of lazy illumination evaluation, used in the caching approaches, from the spatial to the directional domain. Using importance sampling allows us to apply caching not only on low-gloss but also on shiny materials with high-frequency BRDFs, for which the radiance caching algorithm breaks down.
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    An adaptive Discretization Method For Radiosity
    (Blackwell Science Ltd and the Eurographics Association, 1992) Languenou, Eric; Bouatouch, Kadi; Tellier, Pierre
    When using radiosiiy, the visual quality of the rendered images strongly depends on the method employed for discretizing the scene into patches. A too fine discretization may give rise to artifacts, while with a coarse discretization areas with high radiosity gradient may appear. To overcome these problems, the discretization must adapt to the scene. That is, the interaction between two patches must account for the distance between them as well as their surface area. In other words, surfaces far away are discretized less finely than nearby surfaces. These aspects are considered by the new adaptive discretiration method described in this paper. It performs both discretization and system resolution at each iteration of the shooting process, allowing then interactivity.
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    A Progressive Algorithm for Three Point Transport
    (Blackwell Publishers Ltd and the Eurographics Association, 1999) Dumont, Reynald; Bouatouch, Kadi; Gosselin, Philippe
    When computing global illumination in environments made up of surfaces with general Bidirectional Reflection Distribution Functions, 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 hierarchical three point algorithm to compute global illumination in the presence of glossy reflection. We present in this paper some improvements we brought to this method: shooting, "lazy" push-pull, photometric subdivision criterion, etc. Then we will show how our new method takes into account non-planar surfaces in the hierarchical resolution process.
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    Improving Performance and Accuracy of Local PCA
    (The Eurographics Association and Blackwell Publishing Ltd., 2011) Gassenbauer, Václav; Krivánek, Jaroslav; Bouatouch, Kadi; Bouville, Christian; Ribardière, Mickaël; Bing-Yu Chen, Jan Kautz, Tong-Yee Lee, and Ming C. Lin
    Local Principal Component Analysis (LPCA) is one of the popular techniques for dimensionality reduction and data compression of large data sets encountered in computer graphics. The LPCA algorithm is a variant of kmeans clustering where the repetitive classification of high dimensional data points to their nearest cluster leads to long execution times. The focus of this paper is on improving the efficiency and accuracy of LPCA. We propose a novel SortCluster LPCA algorithm that significantly reduces the cost of the point-cluster classification stage, achieving a speed-up of up to 20. To improve the approximation accuracy, we investigate different initialization schemes for LPCA and find that the k-means++ algorithm [AV07] yields best results, however at a high computation cost. We show that similar ideas that lead to the efficiency of our SortCluster LPCA algorithm can be used to accelerate k-means++. The resulting initialization algorithm is faster than purely random seeding while producing substantially more accurate data approximation.
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    Automatic Aesthetics-based Lighting Design with Global Illumination
    (The Eurographics Association, 2014) Léon, Vincent; Gruson, Adrien; Cozot, Rémi; Bouatouch, Kadi; John Keyser and Young J. Kim and Peter Wonka
    In computer graphics, lighting plays an important role in the appearance of a scene. A change in the configuration of light sources can lead to different aesthetics in the final rendered image. Lighting design becomes increasingly complex when using sophisticated global illumination techniques. In this paper, we present a new approach to automatically design the lighting configuration according to the aesthetic goal specified by the user as a set of target parameters. Target parameters are used to set up an objective function which is minimized using an optimization method. The results show that our method can be used to automatically design a lighting configuration that will give to the final image a classic photographic look.
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    Bayesian and Quasi Monte Carlo Spherical Integration for Illumination Integrals
    (The Eurographics Association, 2014) Marques, Ricardo; Bouville, Christian; Bouatouch, Kadi; Nicolas Holzschuch and Karol Myszkowski
    The spherical sampling of the incident radiance function entails a high computational cost. Therefore the illumination integral must be evaluated using a limited set of samples. Such a restriction raises the question of how to obtain the most accurate approximation possible with such a limited set of samples. We need to ensure that sampling produces the highest amount of information possible by carefully placing the limited set of samples. Furthermore we want our integral evaluation to take into account not only the information produced by the sampling but also possible information available prior to sampling. In this tutorial we focus on the case of hemispherical sampling for spherical Monte Carlo (MC) integration. We will show that existing techniques can be improved by making a detailed analysis of the theory of MC spherical integration. We will then use this theory to identify and improve the weak points of current approaches, based on very recent advances in the fields of integration and spherical Quasi-Monte Carlo integration.
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    Experimenting with a Parallel Ray-Tracing Algorithm on a Hypercube Machine
    (Eurographics Association, 1988) Priol, Thierry; Bouatouch, Kadi
    A parallel space tracing algorithm is presented. It subdivides the scene into regions. These latter are distributed among the processors of an iPSC hypercube machine designed by Intel company. Each processor subdivides its own region into cells to accelerate the ray tracing algorithm. Processors communicate by means of messages. The pyramidal shape of the regions allows the deletion of the primary ray messages. A method of performing a roughly uniform load distribution is proposed.
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    Example‐Based Colour Transfer for 3D Point Clouds
    (© 2021 Eurographics ‐ The European Association for Computer Graphics and John Wiley & Sons Ltd, 2021) Goudé, Ific; Cozot, Rémi; Le Meur, Olivier; Bouatouch, Kadi; Benes, Bedrich and Hauser, Helwig
    Example‐based colour transfer between images, which has raised a lot of interest in the past decades, consists of transferring the colour of an image to another one. Many methods based on colour distributions have been proposed, and more recently, the efficiency of neural networks has been demonstrated again for colour transfer problems. In this paper, we propose a new pipeline with methods adapted from the image domain to automatically transfer the colour from a target point cloud to an input point cloud. These colour transfer methods are based on colour distributions and account for the geometry of the point clouds to produce a coherent result. The proposed methods rely on simple statistical analysis, are effective, and succeed in transferring the colour style from one point cloud to another. The qualitative results of the colour transfers are evaluated and compared with existing methods.