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Item A Means to Improve the GKS-3D/PHIGS Output Pipeline Implementation(Eurographics Association, 1987) Herman, Ivan; Reviczky, JanosThe 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.Item On The Projective Invariant Representation of Conies in Computer Graphics(Blackwell Publishing Ltd and the Eurographics Association, 1989) Herman, IvanA general formulation for conies and conic arcs for the purpose of computer graphics is given, based on principles and theorems of projective geometry. This approach allows the approximation of these curves by line segments to be postponed in the graphics output pipeline- it results in a more compact storage, faster approximation algorithms and smoother outlook of the curves.Item 2.5 Dimensional Graphics Systems(Eurographics Association, 1989) Herman, IvanThe outline of an extension of traditional 2D graphics systems is given. This extension is aimed at supporting a three dimensional application program, without incorporating full viewing into the general graphics system itself. The resulting system might be very advantageous for large application programs which have their own three dimensional facilities.Item Modelling Clip: Some More Results(Blackwell Publishing Ltd and the Eurographics Association, 1990) Hubl, Josef; Herman, IvanThe modedling clip of the PHIGS ISO Standard is mathematically analysed. The most important result of this analysis is the fact that the projective image of a modding clip body (that is a not necessarily bounded convex body in space) is simply the union of two convex bodies. Furthermore, it will also be proved that in some cases one of these two bodies is empty. This fact makes the implementation of the modelling clip fairly straightforward and makes it also possible to use all already existing results on clipping against general convex bodies without change.Item Tree Visualisation and Navigation Clues for Information Visualisation(Blackwell Publishers Ltd and the Eurographics Association, 1998) Herman, Ivan; Delest, Maylis; Melancon, GuyInformation visualisation often requires good navigation aids on large trees, which represent the underlying abstract information. Using trees for information visualisation requires novel user interface techniques, visual clues, and navigational aids. This paper describes a visual clue: using the so-called Strahler numbers, a map is provided that indicates which parts of the tree are interesting. A second idea is that of "folding" away subtrees that are too "different" in some sense, thereby reducing the visual complexity of the tree. Examples are given demonstrating these techniques, and what the further challenges in this area are.Item 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.Item New Methods for Improving the GKS Fill Area Output Primitive(Blackwell Publishing Ltd and the Eurographics Association, 1987) Herman, Ivan; Reviczky, JanosThe fill area primitive is one of the most powerful primitives of GKS and its derivatives (GKS-3D, PHIGS etc.). Since its specrfication is extremely general, it is important to explore new approaches to achieve higher performance in its implementation. In this paper fast algorithms are presented for special situations, which can be included, together with appropriate tests, into a complete GKS output pipeline. As a result, a speed improvement With a factor of two may be achieved in important practical cases.