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Item A New Algorithm of Space Tracing Using a CSG Model(Eurographics Association, 1987) Bouatouch, Kadi; Madani, M.O.; Priol, Thierry; Arnaldi, BrunoThis paper describes a new algorithm of space tracing. Scenes are modeled by a CSG tree. Space is subdivided regularly into 3D regions called boxes. With each box is associated a subtree which is the restriction of the whole scene CSG tree to primitives belonging to this box. A 3D grid is used to access boxes.Item An adaptive Discretization Method For Radiosity(Blackwell Science Ltd and the Eurographics Association, 1992) Languenou, Eric; Bouatouch, Kadi; Tellier, PierreWhen 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.Item Experimenting with a Parallel Ray-Tracing Algorithm on a Hypercube Machine(Eurographics Association, 1988) Priol, Thierry; Bouatouch, KadiA 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.Item A VLSI Chip for Ray Tracing Bicubic Patches(Eurographics Association, 1989) Bouatouch, Kadi; Saouter, Yannick; Candela, Jean CharlesThis paper deals with the integration of a VLSI chip dedicated to ray tracing bicubic patches. A recursive subdivision algorithm is embedded in this chip. The recursion stops when the termination conditions are met. A software implementation allowed for the determination of key parameters which influenced the choice of the proposed chip' architecture. Only some modules of the chip are, at the present time, simulated and laid out, the rest is being implemented. A detailed description of the chip' modules is given.Item Theoretical Developments on Polygonal Approximation of Parametric Surfaces for Ray Tracing(Blackwell Publishing Ltd and the Eurographics Association, 1988) Bouatouch, KadiSome theoretical extensions are brought to Koparkar and Mudur s method which deals with a polygonal approximation of parametric surfaces using potential extrema. The proposed extensions allow the determination of both the existence and the equation of a curve solution of potential extrema. Solutions are given to solve the crack problem and to avoid the artificats due to an inexact ray-surface intersection point near the silhouette or on the higher curvature regions. Moreover, two methods of ray tracing surfaces are proposed.Item Low Sampling Densities using a psychovisual approach(Eurographics Association, 1991) Bouville, Christian; Tellier, Pierre; Bouatouch, KadiIt has long been observed that the keenness of sight is lower for diagonal directions than for horizontal or vertical ones. This anisotropy of the human eye response can be exploited by using a non-orthogonal sampling pattern with a reduced sampling density. After an introduction to the two-dimensional sampling theory, it is shown that quincunx sampling is well suited to this characteristic. Then a sampling scheme based on this approach is described. This effectively leads to halving the sampling density and thereby the computing time of ray-traced pictures.Item Fast Wavelet Radiosity Method(Blackwell Science Ltd and the Eurographics Association, 1994) Pattanaik, Sumanta N.; Bouatouch, KadiWavelet analysis has been found [1] to be very useful for functional representation and accurate global solution of radiosity. In radiosity we deal with functions in 2D and 4D spaces. Under such conditions, the biggest bottleneck in applying this wavelet analysis seems to be the large number of multidimensional inner products. In this paper, we propose (i) the use of interpolating wavelets for fast inner product computation and consequently for faster wavelet radiosity solution (ii) the use of hierarchical decomposition technique for determining the smoothness of the radiosity function for optimal adaptive subdivision.