Issue 4

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https://diglib.eg.org/handle/10.2312/87

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    Announcements
    (Blackwell Publishers Ltd and the Eurographics Association, 1998)
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    Book Reviews
    (Blackwell Publishers Ltd and the Eurographics Association, 1998)
    Books reviewed:Donnelly, Daniel. Web Design: The Next GenerationHege, H.-C. and Polthier, K. (editors). Visualization and MathematicsGibson, J. D., Berger, T., Lookabaugh, T., Lindbergh, D. andBaker, R. L. Digital Compression for MultimediaMorgan, Don. Numerical Methods For DSP Systems in CWainer, Howard. Visual Revelations: Graphical Tales of Fate and Deception from Napoleon Bonaparte to Ross PerotMaestri, George. Digital Character AnimationKlimek, Grazyna and Klimek, Maciej. Discovering Curves and Surfaces with MapleTrappl, Robert and Petta, Paolo (editors). Creating Personalities for Synthetic ActorsLohmann, Gabriele. Volumetric Image AnalysisMeinhardt, Hans. The Algorithmic Beauty of Sea Shells (2nd Edition)Palanque, Philippe and Paterno, Fabio (editors) Formal Methods in Human-Computer InteractionDai, Fan (editor). Virtual Reality for Industrial Applications
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    A Fast Algorithm for Inverse Colormap Computation
    (Blackwell Publishers Ltd and the Eurographics Association, 1998) Brun, L.; Secroun, C.
    The inverse colormap operation is the process which allows an image to be displayed with a limited set of colors. In order to obtain a minimal visual distortion between the input image annd the one displayed, inverse colormap algorithms associate each color with its nearest representative. The method presented in this paper is carried out in two steps. First, the 3D Voronoi diagram implicitly used by inverse colormap algorithms is approximated using a Karhunen-Loeve transformation. Then, a correcting step is carried out in order to reduce the in uence of the first approximation. The complexity of our algorithm is independent of the size of the colormap. Moreover, its results are equal or quite close to the optimal solution.
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    Calendar of Events
    (Blackwell Publishers Ltd and the Eurographics Association, 1998)
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    Incident Light Metering in Computer Graphics
    (Blackwell Publishers Ltd and the Eurographics Association, 1998) Neumann, Laszlo; Matkovic, Kresimir; Neumann, Attila; Purgathofer, Werner
    Every rendering process consists of two steps. The first is the computing of luminance values by methods like ray tracing or radiosity, and the second step is the mapping of the computed values to values appropriate for displaying. In the last years, as alternative to simple linear scaling which maps the average value to the medium luminance, some new ways of mapping were introduced. These new methods are based on photography analogies and on human vision models. All existing methods follow, implicitly or explicitly, the reflected light metering principle. The method introduced in this paper is the first that follows the incident light metering used in professional photography and in the movie industry. Actually the irradiances are measured using a set of diffusors, which are placed automatically in the scene, and a linear scale factor based on these measurements is used to map the computed radiances to the display device. The diffusors act as half space integrators, they collect the light energy from all half space directions. The light comes from the primary light sources, or it is the result of various interreflections. The newly introduced method reproduces original colors faithfully even for scenes with very low or very high average reflectivity.
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    Event Reports
    (Blackwell Publishers Ltd and the Eurographics Association, 1998)
    Eurographics â 98 Conference, page 301Eurographics â 98 Awards, page 303EG UK â 98 Conference, page 304Cover Competition Winners, page 306
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    1998 Annual Index
    (Blackwell Publishers Ltd and the Eurographics Association, 1998)
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    Announcements
    (Blackwell Publishers Ltd and the Eurographics Association, 1998)
    Join Now! Network Service
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    Reference Models for Distributed Cooperative Visualization
    (Blackwell Publishers Ltd and the Eurographics Association, 1998) Duce, D. A.; Giorgetti, D.; Cooper, C. S.; Gallop, J. R.; Johnson, I. J.; Robinson, K.; Seelig, C. D.
    In this paper reference models for visualization systems that have appeared in the literature are surveyed and a new reference model for distributed cooperative visualization developed in the MANICORAL project (funded by the EU Telematics Programme) is described. The relationship of earlier models to the new model is discussed. A number of cooperative visualization systems that have been reported in the literature are compared in the framework of the MANICORAL model.
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    Eurographics Reports
    (Blackwell Publishers Ltd and the Eurographics Association, 1998)
    EG UK 17th Annual General Meeting, page 307, General Assembly Minutes, page 309
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    An Exhaustive Error-Bounding Algorithm for Hierarchical Radiosity
    (Blackwell Publishers Ltd and the Eurographics Association, 1998) Holzschuch, Nicolas; Sillion, Francois
    This paper presents a complete algorithm for the evaluation and control of error in radiosity calculations. Providing such control is both extremely important for industrial applications andd one of the most challenging issues remaining in global illumination research. In order to control the error, we need to estimate the accuracy of the calculation while computing the energy exchanged between two objects. Having this information for each radiosity interaction allows to allocate more resources to refine interactions with greater potential error, and to avoid spending more time to refine interactions already represented with sufficient accuracy. Until now, the accuracy of the computed energy exchange could only be approximated using heuristic algorithms. This paper presents the first exhaustive algorithm to compute fully reliable upper and lower bounds on the energy being exchanged in each interaction. This is accomplished by computing first and second derivatives of the radiosity function where appropriate, and making use of two concavity conjectures. These bounds are then used in a refinement criterion for hierarchical radiosity, resulting in a global illumination algorithm with complete control of the error incurred. Results are presented, demonstrating the possibility to create radiosity solutions with guaranteed precision. We then extend our algorithm to consider linear bounding functions instead of constant functions, thus creating simpler meshes in regions where the function is concave, without loss of precision. Our experiments show that the computation of radiosity derivatives along with the radiosity values only requires a modest extra cost, with the advantage of a much greater precision.
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    Programming Paradigms in an Object-Oriented Multimedia Standard
    (Blackwell Publishers Ltd and the Eurographics Association, 1998) Duke, D. J.; Herman, I.
    Of the various programming paradigms in use today, object-orientation is probably the most successful in terms of industrial take-up and application, particularly in the field of multimedia. It is therefore unsurprising that this technology has been adopted by ISO/IEC JTC1/SC24 as the foundation for a forthcoming International Standard for Multimedia, called PREMO. Two important design aims of PREMO are that it be distributable, and that it provides a set of media-related services that can be extended in a disciplined way to support the needs of future applications and problem domains. While key aspects of the object-oriented paradigm provide a sound technical basis for achieving these aims, the need to balance extensibility and a high-level programming interface against the realities of efficiency and ease of implementation in a distributed setting meant that the task of synthesising a Standard from existing practice was non-trivial. Indeed, in order to meet the design aims of PREMO is was found necessary to augment the basic object infrastructure with facilities and ideas drawn from other programming paradigms, in particular concepts from constraint management and data flow. This paper describes the important trade-offs that have affected the development of PREMO and explains how these are addressed through the use of specific programming paradigms.
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    Calendar of Events
    (Blackwell Publishers Ltd and the Eurographics Association, 1998)
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    Editorial
    (Blackwell Publishers Ltd and the Eurographics Association, 1998) Coquillart, Sabine; Seidel, Hans-Peter