Volume 05 (1986)
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Item A Monte Carlo Approach for ? Placement in Fractal-Dimension Calculations for Waveform Graphs(Blackwell Publishing Ltd and the Eurographics Association, 1986) Pickover, C.A.Many diverse and complicated objects of nature and math possess the quality of self-similarity, and algorithms which produce self-similar shapes provide a way for computer graphics to represent natural structures. For a variety of studies in signal processing and shape-characterization, it is useful to compare the structures of many different "objects". Unfortunately, large amounts of computer time are needed as prerequisite for rigorous self-similarity characterization and comparison. The present paper describes a fast computer technique for the characterization of self-similar shapes and signals based upon Monte Carlo methods. The algorithm is specifically designed for digitized input (e.g. pictures, acoustic waveforms, analytic functions) where the self-similarity is not obvious from visual inspection of just a few sample magnifications. A speech waveform graph is used as an example, and additional graphics are included as a visual aid for conceptualizing the Monte Carlo process when applied to speech waveforms.Item EUROGRAPHICS Membership(Blackwell Publishing Ltd and the Eurographics Association, 1986)Item Algorithms for Handling the Fill Area Primitive of GKS(Blackwell Publishing Ltd and the Eurographics Association, 1986) Shinde, Yogesh N.; Mudur, S.P.The fill area primitive of GKS (Graphical Kernel System)1 is one of the more powerful features which differentiates it from earlier device independent graphics software and systems. Its specification is extremely general in the form of a closed boundary, possibly self-intersecting, and whose interior can be filled in a variety of styles. However a complete implementation of this primitive is very complex. It is difficult to find a single graphics workstation incorporating this primitive in hardware or firmware. Most GKS implementations will have to include software for simulating the appearance of this primitive on the commonly available displays and hard-copy graphics devices. Correct and efficient algorithms are necessary for developing this software. Because of the generality many of the existing algorithms are not directly applicable. In this paper we describe:1. a new algorithm for clipping a fill area polygon, using what we have named as the Bridge Technique.2. implementation of a plane sweep algorithm, by Nievergelt and Preparata,2 for solid filling and hatching, particularly applicable to vector devices.3. extension of the plane sweep algorithm for filling with any given pattern on raster as well as vector devices.The algorithms have been designed to work for all special cases as well. In fact they have been implemented having in mind the fill area set primitive of GKS-3D extension.3 All these algorithms have been very successfully implemented in a commercially available GKS implementation, namely indoGKS.Item Two Algorithms for Decomposing a Polyhedron into Convex Parts(Blackwell Publishing Ltd and the Eurographics Association, 1986) Szilvasi-Nagy, M.Two algorithms are presented for splitting a polyhedron into convex components: one for the case of a simple polyhedron and one for a more general case, when the polyhedron may have ring-shaped faces and cavities. The time requirement in both cases is O(DNlogN), where D is the number of concave dihedral angles and N is the number of edges. The algorithm for the simple oasis produces at most D+ 1 convex pieces which is the minimal number of the convex components.Item Calendar of Events(Blackwell Publishing Ltd and the Eurographics Association, 1986)Item EDITORIAL(Blackwell Publishing Ltd and the Eurographics Association, 1986)Item EUROGRAPHICS -86 - A Personal View(Blackwell Publishing Ltd and the Eurographics Association, 1986) Morrow, T. M.Item Calendar of Events(Blackwell Publishing Ltd and the Eurographics Association, 1986)Item Overlap Operations and Raster Graphics(Blackwell Publishing Ltd and the Eurographics Association, 1986) Thomas, A.L.This paper outlines the development of a volume and surfaces modelling system for use with raster graphic displays. The ideas are presented in a historical framework to make the reasoning behind the design decisions clear and to indicate the main influences which have guided the work. There are two outcomes of importance: a language form for defining volumes and surfaces and hardware to convert this representation directly into a display. The hardware provides hidden-line or hidden-area removal as a display primitive which, in an appropriate implementation, can be fast enough to support a range of real-time display applications. Linked to this hidden-line, hidden-area removal facility is an ability to provide interference tests for objects that are being moved around in a scene. Again there appears to be a hierarchy of applications ranging in complexity from interactive volume editing to robot control and vision systems. The new facilities complement existing point and line based display operations, on which most current displays- hardware is based. A good case is emerging for integrating the two approaches into a single hardware implementation for CAD workstations and for simulator display systems.Item EUROGRAPHICS General Assembly(Blackwell Publishing Ltd and the Eurographics Association, 1986)Item International Cooperation for Computer Graphics(Blackwell Publishing Ltd and the Eurographics Association, 1986) Sneddon, MarkItem Calendar of Events(Blackwell Publishing Ltd and the Eurographics Association, 1986)Item Offers to EUROGRAPHICS Members(Blackwell Publishing Ltd and the Eurographics Association, 1986)Item Biom orphs: Computer Displays of Biological Forms Generated from Mathematical Feedback Loops(Blackwell Publishing Ltd and the Eurographics Association, 1986) Pickover, C.A.A computer graphics algorithm is used to create complicated forms resembling invertebrate organisms. These natural morphologies are generated through the iteration of mathematical transformations. Several illustrations are chosen as examples of the diversity of biological structures which result from this technique.Item EDITORIAL(Blackwell Publishing Ltd and the Eurographics Association, 1986) Arnold, David; Enderle, GuenterItem Proposed Revisions to the EUROGRAPHICS UK Chapter Constitution(Blackwell Publishing Ltd and the Eurographics Association, 1986)Item Image Generation by Space Sweep(Blackwell Publishing Ltd and the Eurographics Association, 1986) Muller, H.A method of using spatial coherence in image generation by raytracing is presented. The idea is to trace a set of rays in parallel. This is carried out by space sweep. Space sweep consists of moving a plane through the object space. The rays intersected by the plane are organized into a dynamic data structure R for range searching. When an object is met by the sweeping plane, those rays intersecting the object are found by a range search with the object in R. Exact complexity bounds are given for this algorithm, as well as details to allow practical application of this approach in image operation.Item EUROGRAPHICS -87 Welcome to Amsterdam(Blackwell Publishing Ltd and the Eurographics Association, 1986)Item The Association for Computing in Art and Design Education (ACADE)(Blackwell Publishing Ltd and the Eurographics Association, 1986)Item EUROGRAPHICS -87 - Amsterdam(Blackwell Publishing Ltd and the Eurographics Association, 1986)