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Now showing 1 - 10 of 89
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    Evaluation of Standard Graphics Packages
    (Blackwell Publishing Ltd and the Eurographics Association, 1987) Klok, Fopke
    In order to compare the quality of different implementations of GKS, the ISO0 standard for computer graphics, an evaluation method for GKS implementations is presented. It is based upon several groups of criteria. One group of criteria is concerned with performance, by which we understand here the memory requirements and time requirements for programs using GKS functions. A program that measures the performance of GKS packages is presented. Results of this evaluation method with several commercially available GKS implementations are described in summary. A checklist for evaluation of standard graphics packages is added as an appendix.
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    Ray Tracing Rational B-Spline Patches in VLSI
    (The Eurographics Association, 1987) Schneider, Bengt-Olaf; Fons Kuijk and Wolfgang Strasser
    Rational B-spline surfaces make it possible to merge the concepts of freeform surfaces and that of surfaces described by rational polynomials especially conic sections. For ray tracing it is crucial to determine the intersection between ray and object. Therefore an algorithm is developed that is suitable for a VLSI implementation. Some alternatives for the implementation of this algorithm are presented and discussed. The paper concludes with a discussion of some problems and possible further developments.
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    A Means to Improve the GKS-3D/PHIGS Output Pipeline Implementation
    (Eurographics Association, 1987) Herman, Ivan; Reviczky, Janos
    The output pipeline of GKS-3D/PHIGS isexamined to find some possible points where the implementation could be improved to raise efficiency while remaining strictly within the scope of the Standards. Some interesting results are presented in the paper which have led to a 25-30% improvement in speed when compared to a more conservative implementation.
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    An O(log N) Parallel Time Exact Hidden-LineAlgorithm
    (The Eurographics Association, 1987) Dévai, F.; Fons Kuijk and Wolfgang Strasser
    "Parallel algorithms are given for the exact solution of the hidden-line problem. Most of the parallel algorithms proposed for visibility problems in the literature give approximate solutions. and thus cannot yield an upper bound on the complexity of the particular problem. The first algorithm proposed here is worth mentioning not only for its simplicity. but also from a practical point of view: a speed up of a factor P is achieved by using P processors. l"";;P"";;N. where N is the number of edges used to describe a polygonal scene. Additionally. the problem of aliasing inherent with approximation methods is avoided.The significance of the second algorithm, which is based on the first one, is mainly on the theoretical level: it is used to establish the parallel complexity of the hidden-line problem. The sequential complexity of this problem has recently been proved to be e(N2). and now we can prove that in the parallel case the problem is in the complexity class NC, Le., it can be solved in time polynomial in logN by using a number of processors polynomial in N, assuming any reasonable model of parallel computation. More particularly, an O(logN) parallel time solution is given which cannot be further improved even if arbitrarily many processors of a concurrent read, exclusive write parallel RAM model are available."
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    Display of Solid Models with a Multi-Processor System
    (Eurographics Association, 1987) Jansen, Frederik W.; Sutherland, Robert J.
    There is a growing need for fast high-quality display of solid objects. Recently-developed custom-VLSI hardware offers high-speed display but lacks the flexibility and processing power at the pixel level to sustain the calculations and filter operations needed for realistic reflection models, texture mapping and anti-aliasing. Multi-processor systems built with general-purpose components of relatively high capacity and moderate cost provide an alternative; they also offer higher performance than single processor systems but retain their flexibility. A CSG hidden-surface algorithm based on depth-buffering and image subdivision is presented which is suitable for use with such a multi-processor system.
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    A New Algorithm of Space Tracing Using a CSG Model
    (Eurographics Association, 1987) Bouatouch, Kadi; Madani, M.O.; Priol, Thierry; Arnaldi, Bruno
    This 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.
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    A New Scan Line Algorithm for the Rendering of CGS Trees
    (Eurographics Association, 1987) Pueyo, Xavier; Mendoza, Joan Carles
    A scan line algorithm is proposed to render CSG modelled solids. Scan planes intersections are obtained by means of a proposed generalisation of Porter’s algorithm. 2-D scan plane primitives are decomposed in a way that provides a more accurate disjointness information then 3-D inclosing boxes and a simple way to class spans. Furtheremore, this scan plane organisation allows the use of most of scan line hidden surface strategies that make use of different types of coherence to speed up the visibility process.
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    An Intersecting Modification to the Bresenham Algorithm
    (Blackwell Publishing Ltd and the Eurographics Association, 1987) Skala, Viclav
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    New Algorithms for Computer Graphics
    (The Eurographics Association, 1987) Ovennars, Mark H.; Fons Kuijk and Wolfgang Strasser
    "IntroductionThe area of computational geometry deals with the study of algorithms for problems concerning geometric objects like e.g. lines, polygons, circles, etc. in the plane and in higher dimensional space. Since its introduction in 1976 by Shamos the field has developed rapidly and nowadays there are even special conferences and journals devoted to the topic. A list of publications by Edelsbrunner and van Leeuwen [6] collected in 1982 already contained over 650 papers. And this number has rapidly increased since then."
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    Generative Scene Modelling
    (Eurographics Association, 1987) Beyer, Thomas; Friedell, Mark
    We describe a new theory of scene modelling that includes generative processes as integral components of scene descriptions. A single, uniform treatment of generative processes replaces the variety of ad hoc mechanisms commonly in use. We discuss the implementation of the theory in an experimental modelling system and show that L-systems, fractals, and particle systems, as well as many specialized generative processes, become comparatively easy to define and use.