Has files: true × Start date: 2000 × Author: Bouatouch, Kadi × End date: 2009 ×

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Now showing 1 - 7 of 7
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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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    Making Radiance and Irradiance Caching Practical: Adaptive Caching and Neighbor Clamping
    (The Eurographics Association, 2006) Krivánek, Jaroslav; Bouatouch, Kadi; Pattanaik, Sumanta; Zára, Jirí; Tomas Akenine-Moeller and Wolfgang Heidrich
    Radiance and irradiance caching are efficient global illumination algorithms based on interpolating indirect illumination from a sparse set of cached values. In this paper we propose an adaptive algorithm for guiding spatial density of the cached values in radiance and irradiance caching. The density is adapted to the rate of change of indirect illumination in order to avoid visible interpolation artifacts and produce smooth interpolated illumination. In addition, we discuss some practical problems arising in the implementation of radiance and irradiance caching, and propose techniques for solving those problems. Namely, the neighbor clamping heuristic is proposed as a robust means for detecting small sources of indirect illumination and for dealing with problems caused by ray leaking through small gaps between adjacent polygons.
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    Radiance Cache Splatting: A GPU-Friendly Global Illumination Algorithm
    (The Eurographics Association, 2005) Gautron, Pascal; Krivánek, Jaroslav; Bouatouch, Kadi; Pattanaik, Sumanta; Kavita Bala and Philip Dutre
    Fast global illumination computation is a challenge in several fields such as lighting simulation and computergenerated visual effects for movies. To this end, the irradiance caching algorithm is commonly used since it provides high-quality rendering in a reasonable time. However this algorithm relies on a spatial data structure in which nearest-neighbors queries and data insertions are performed alternately within a single rendering step. Due to this central and permanently modified data structure, the irradiance caching algorithm cannot be easily implemented on graphics hardware. This paper proposes a novel approach to global illumination using irradiance and radiance cache: the radiance cache splatting. This method directly meets the processing constraints of graphics hardware since it avoids the need of complex data structure and algorithms. Moreover, the rendering quality remains identical to classical irradiance and radiance caching. Our renderer shows an implementation of our algorithm which provides a significant speedup compared to classical irradiance caching.
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    A Novel Hemispherical Basis for Accurate and Efficient Rendering
    (The Eurographics Association, 2004) Gautron, Pascal; Krivanek, Jaroslav; Pattanaik, Sumanta; Bouatouch, Kadi; Alexander Keller and Henrik Wann Jensen
    This paper presents a new set of hemispherical basis functions dedicated to hemispherical data representation. These functions are derived from associated Legendre polynomials. We demonstrate the usefulness of this basis for representation of surface reflectance functions, rendering using environment maps and for efficient global illumination computation using radiance caching. We show that our basis is more appropriate for hemispherical functions than spherical harmonics. This basis can be efficiently combined with spherical harmonics in applications involving both hemispherical and spherical data.
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    A Directional Occlusion Shading Model for Interactive Direct Volume Rendering
    (The Eurographics Association and Blackwell Publishing Ltd., 2009) Schott, Mathias; Pegoraro, Vincent; Hansen, Charles; Boulanger, Kévin; Bouatouch, Kadi; H.-C. Hege, I. Hotz, and T. Munzner
    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.
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    A Bayesian Monte Carlo Approach to Global Illumination
    (The Eurographics Association and Blackwell Publishing Ltd, 2009) Brouillat, Jonathan; Bouville, Christian; Loos, Brad; Hansen, Charles; Bouatouch, Kadi
    Most Monte Carlo rendering algorithms rely on importance sampling to reduce the variance of estimates. Importance sampling is efficient when the proposal sample distribution is well-suited to the form of the integrand but fails otherwise. The main reason is that the sample location information is not exploited. All sample values are given the same importance regardless of their proximity to one another. Two samples falling in a similar location will have equal importance whereas they are likely to contain redundant information. The Bayesian approach we propose in this paper uses both the location and value of the data to infer an integral value based on a prior probabilistic model of the integrand. The Bayesian estimate depends only on the sample values and locations, and not how these samples have been chosen. We show how this theory can be applied to the final gathering problem and present results that clearly demonstrate the benefits of Bayesian Monte Carlo.