Issue 3

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https://diglib.eg.org/handle/10.2312/45

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    At Last an ISO C Binding of GKS
    (Blackwell Science Ltd and the Eurographics Association, 1991) Bakker, Miente
    The C4 bindings of GKS1 and other semantic computer graphics standards like GKS-3D2 and PHIGS3 are long overdue. While GKS was completed in 1985 and GKS-3D2 (and PHIGS3) became an international standard in 1988, none of their C bindings could be standardized, for the simple reason that the C language itself was not a standard. Instead, a host of de facto GKS/C bindings9 appeared.This paper will give the flavour of the ISO C binding5,6 of GKS- the main features will be outlined.1983 CR Categories: D.3.0,I.3.0,I.3.4.
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    Cartographic Algorithms: Problems of Implementation and Evaluation and the Impact of Digitising Errors
    (Blackwell Science Ltd and the Eurographics Association, 1991) Visvalingam, M.; Whyatt, J.D.
    Cartographic generalisation remains one of the outstanding challenges in digital cartography and Geographical Information Systems (GIS). It is generally assumed that computerisation will lead to the removal of spurious variability introduced by the subjective decisions of individual cartographers. This paper demonstrates through an in-depth study of a line simplification algorithm that computerisation introduces its own sources of variability. The algorithm, referred to as the Douglas-Peucker algorithm in cartographic literature, has been widely used in image processing, pattern recognition and GIS for some 20 years. An analysis of this algorithm and study of some implementations in wide use identify the presence of variability resulting from the subjective decisions of software implementors. Spurious variability in software complicates the processes of evaluation and comparison of alternative algorithms for cartographic tasks. No doubt, variability in implementation could be removed by rigorous study and specification of algorithms. Such future work must address the presence of digitising error in cartographic data. Our analysis suggests that it would be difficult to adapt the Douglas-Peucker algorithm to cope with digitising error without altering the method.
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    Computer Art from Numerical Methods
    (Blackwell Science Ltd and the Eurographics Association, 1991) Szyszkowicz, Mieczyslaw
    Zero-finding methods, Euler s method and the numerical algorithms elaborated as package subroutines are studied by using a computer graphics technique. The patterns obtained show chaotic behaviour (science) and beauty of numerical algorithms (art).
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    Fat curves
    (Blackwell Science Ltd and the Eurographics Association, 1991) Yao, C.; Rokne, J.
    Fat curves in two-dimensional Euclidean space are discussed. Previous work on fat curves is reviewed and a new definition is given for a fat curve having a smooth axis. The joining of two fat curves is discussed and a technique for scan-converting fat curves is presented.
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    The GKS Input Model in Manifold
    (Blackwell Science Ltd and the Eurographics Association, 1991) Soede, Dirk; Arbab, Farhad; Herman, Ivan; Ten Hagen, Paul J. W.
    This paper describes the specification of the GKS input model in Manifold. The aim of the work reported in this paper was two-fold: first, to review the communication patterns implied by the GKS input model, and second, to evaluate the suitability of the Manifold language as a tool for defining complex dynamic interaction patterns that are common in non-trivial user interfaces.The GKS input model is also adopted by all more recent ISO graphics standard documents. A more formal scrutiny of the inter-communication of the components of this model, excluding the implementation details of their functionality, is instructive in itself. It can reveal directions for improvement of its shortcomings and for generalization of its strengths for the ongoing effort to define the functionality of future graphics packages.Manifold is a language for describing inter-process communications. Processes in Manifold communicate by means of buffered communication links called streams and by reacting to events raised asynchronously by other processes. Our experience shows that Manifold is a promising tool for describing systems of cooperating parallel processes. Our Manifold specification of the GKS input model offers a very flexible way to structure user defined logical input devices. Furthermore, it is simple and modular enough to allow easy extensions to include more functionality by local modifications. As such, it can serve as a basis for possible extensions and enhancements envisioned for future graphics packages.1987 CR Categories: C.1.2, C.1.3, C.2.m, D.1.3, F.1.2, I.1.3, I.3.6, I.3.4.1885 Mathematical Subject Classification: 68N99, 68Q10,68U05.
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    Search for the Intersection Polygon of any Two Polygons: Application to the Garment Industry
    (Blackwell Science Ltd and the Eurographics Association, 1991) Mangen, Alain; Lasudry, Nadine
    One of the biggest problems usually encountered by the clothes manufacturer consists of placing various pattern parts on a rectangular area in such a way that the waste of material between the pieces is minimized.To bring some automated help in this field, computer programs need first to handle the complicated contours of the pieces. One needs not only to check the overlap of two contiguous patterns, but also to compute their precise area of intersection, allowing in this way the use of some kind of combinatorial optimization.In a wider context, it is possible to design a general purpose algorithm, able to build the complete structure representing the intersection of two polygons. It is remarkable that the same algorithm can also be used, with only a few modifications, to compute the union and the difference of any two polygons.