Issue 4

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https://diglib.eg.org/handle/10.2312/92

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    Adaptable Splatting for Irregular Volume Rendering
    (Blackwell Publishers Ltd and the Eurographics Association, 1999) Wang, Wencheng; Wu, Enhua
    By employment of a footprint table in conducting intensity integration, splatting method has been very successful in rendering regular data volumes. Recently, the method has also been extended to render irregular data volumes. However, since samples in irregular volumes vary greatly in size and shape, the footprint table is unable to be employed in an efficient manner. This hinders the application of splatting approach from being used in the irregular volume case. In this paper, an adaptable splatting method is proposed, which provides an efficient way to integrate color intensity in terms of footprint table for the samples in various sizes. Experiments show that the new method may be used to produce better images without extra expense.
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    Announcements
    (Blackwell Publishers Ltd and the Eurographics Association, 1999)
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    Book Reviews
    (Blackwell Publishers Ltd and the Eurographics Association, 1999)
    Books reviewed:Maeda, John. Design by NumbersKnuth, Donald E. Digital TypographyFarin, G., Bieri, H., Brunnet, G. and Derose, T. (Editors). Geometric ModellingKnudson, Jonathan. Java 2D GraphicsHege, H.-C. and Polthier, K. (Editors). Mathematical VisualizationPickover, Clifford (Editor). Chaos and Fractals: A Computer Graphical JourneyFlake, Gary William. The Computational Beauty of Nature: Computer Explorations of Fractals, Chaos, Complex Systems and AdaptationStrothotte, Thomas. Computational Visualization, Graphics, Abstraction and InteractivityRuss, John C. The Image Processing Handbook (3rd edition)
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    Editorial
    (Blackwell Publishers Ltd and the Eurographics Association, 1999) Coquillart, Sabine; Seidel, Hans-Peter
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    Eurographics
    (Blackwell Publishers Ltd and the Eurographics Association, 1999)
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    Event Reports
    (Blackwell Publishers Ltd and the Eurographics Association, 1999)
    Eurographics '99Eurographics '99 Awards10th Eurographics Workshop on RenderingSiggraph '992000 Cover Competition
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    G1 Hierarchical Bezier Surface over Arbitrary Meshes
    (Blackwell Publishers Ltd and the Eurographics Association, 1999) Bercovier, M.; Volpin, O.
    This paper presents a method for constructing composite surfaces based on a collection of quadrilateral patches. A global parameterization using bilinear quadrilateral meshes and FEM like minimization procedure are introduced. Smoothing conditions such as C1 and G1 are handled by constraint equation and a related duality argument is implemented. The surfaces that can be constructed in this way include conforming and non-conforming connections (3 n 6, T-nodes) between elementary patches. Non-manifold surfaces are automatically treated also by this data structure. The underlying quadratic programming with linear constraints is solved by duality methods. Hierarchical data structure with bordering matrices methods are implemented to deal with local refinement (subdivision). The present work details the actual implementation for the case of Bezier patches.
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    Hermitian B-Splines
    (Blackwell Publishers Ltd and the Eurographics Association, 1999) Grisoni, Laurent; Blanc, Carole; Schlick, Christophe
    This paper proposes to study a spline model, called HB-splines, that is in fact a B-spline representation of Hermite splines, combined with some restriction on the differential values at segment boundaries. Although this model does not appear able to offer something new to the computer graphics community, we think that HB-splines deserve to be considered for themselves because they embed many interesting features. First, they include all the classical properties required in a geometric modeling environment (convex hull, local control, arbitrary orders of parametric or geometric continuity). Second, they have a nice aptitude for direct manipulation (i.e. manipulation without using control points). For this purpose, we propose a new graphic widget, called control sails, that offers the user an intuitive way to specify local properties (position, tangent, curvature) of a curve or a surface. Finally, they provide an elegant formulation of a biorthogonal wavelet family, that permits multiresolution manipulations of the resulting curves or surfaces, in a very efficient way.
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    Reflectance Models with Fast Importance Sampling
    (Blackwell Publishers Ltd and the Eurographics Association, 1999) Neumann, Laszlo; Neumann, Attila; Szirmay-Kalos, Laszlo
    We introduce a physically plausible mathematical model for a large class of BRDFs. The new model is as simple as the well-known Phong model, but eliminates its disadvantages. It gives a good visual approximation for many practical materials: coated metals, plastics, ceramics, retro-reflective paints, anisotropic and retro-reflective materials, etc. Because of its illustrative properties it can be used easily in most commercial software and because of its low computational cost it is practical for virtual reality. The model is based on a special basic BRDF definition, which meets the requirements of reciprocity and of energy conservation. Then a class of BRDFs is constructed from this basic BRDF with different weight functions. The definition of such weight functions requires the user to specify the profile of the highlights, from which the weight function is obtained by derivation. It is also demonstrated how importance sampling can be used with the new BRDFs.
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    Synchronisation and Load Balancing for Parallel Hierarchical Radiosity of Complex Scenes on a Heterogeneous Computer Network
    (Blackwell Publishers Ltd and the Eurographics Association, 1999) Meneveaux, Daniel; Bouatouch, Kadi
    In this paper we propose a SPMD parallel hierarchical radiosity algorithm relying on a novel partitioning method which may apply to any kind of architectural scene. This algorithm is based on MPI (Message Passing Interface), a communication library which allows the use of either a heterogeneous set of concurrent computers or a parallel computer or both. The database is stored on a common directory and accessed by all the processors (through NFS in case of a network of computers). As the objective is to handle complex scenes such as building interiors, to cope with the problem of memory size, only a subset of the database resides in memory of each processor. This subset is determined with the help of a partitioning into 3D cells, clustering and visibility calculations. A graph expressing visibility between the resulting clusters is determined, partitioned (with a new method based on classification of K-means type) and distributed amongst all the processors. Each processor is responsible for gathering energy (using the Gauss-Seidel method) only for its subset of clusters. In order to reduce the disk transfers due to downloading these subsets of clusters, we use an ordering strategy based on the traveling salesman algorithm. Dynamic load balancing relies on a task stealing approach while termination is detected by configuring the processors into a ring and moving a token around this ring. The parallel iterative resolution is of group iterative type. Its mathematical convergence is proven in the appendix.