EG1981 Proceedings (Technical Papers)

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Graphics Standards - Where are we ?
(The Eurographics Association, 1981) Hagen, Paul J.W. ten; J. L. Encarnacao
An overview is given of the state of the standardization efforts of ISO/TC97/SC5/WG2, which currently concentrate on GKS. The standardization activities are illustrated by presenting a recently incorporated concept of bundling. An outlook on future activities Is presented.
A HARDWARE APPROACH TO THE CORE SYSTEM OF ACM/SIGGRAPH
(The Eurographics Association, 1981) Möller, Gerd; J. L. Encarnacao
A new structure of the picture generation pipeline for a high-performance vector refresh graphic system is proposed. This pipeline consists of a graphic processor calculating the viewing transformations, a refresh buffer storing the partly-transformed display-file, a display processor controlling the refresh, a transformation generator calculating the image transformations and a digital vector and character generator. The realization and the advantages of this graphic system are described.
SGL APPLICATION - DEFINITION AND PRACTICAL USE
(The Eurographics Association, 1981) Cunha, J.D.; J. L. Encarnacao
This paper describes our experience in the development of an application using the SGL system presented in previous publications ( [2] [3] ). Special attention is paid to the pos sibilities and limitations due to GKS concepts (the SGL is implemented on top of the GKS), SGL architecture, computer confi guration and the high-level programming language (SIMULA-67) . The definition of the application and its practical use are con sidered separately.
STATE OF THE ART IN COMPUTER GRAPHICS: A SIGGRAPH PERSPECTIVE
(The Eurographics Association, 1981) Badler, Norman I.; Ellis, Robert A.; J. L. Encarnacao
VOICE RECOGNITION IN A GRAPHIC SYSTEM
(The Eurographics Association, 1981) Gnettner, Wolfgang; J. L. Encarnacao
Voice recognition is discussed as a useful tool in interactive graphics. Two applications in electronical design and surveying are described. First results show an increased input speed, a low error probability and more convenient conditions for work.
A GKS INTERFACE TO A REALTIME ORIENTED RASTER WORKSTATION FOR CAD APPLICATIONS
(The Eurographics Association, 1981) Lindner, R.; Rix, J.; J. L. Encarnacao
The interface of the Graphical Kernel System GKS is examined with respect to the demands of realtime raster graphics. First the computation time for the different transformations is estimated, to show the great gap between the requirements of realtime operations and the capabilities of conventional minicomputers. It is shown, how the GKS interface supports or with some extensions may support the execution of most of the transformations by a special hardware in the raster workstation.
THE GEOMETRIC WORKBENCH (GWB) - AN EXPERIMENTAL GEOMETRIC MODELING SYSTEM
(The Eurographics Association, 1981) Mäntylä, Martti; Takala, Tapio; J. L. Encarnacao
The Geometric workbench (GWB), an experimental. geometric modeling system, is described. It is based on a hybrid representation scheme, where solids are represented by CSG volume trees and boundary representations. Boundary representations are described with so called Euler operators. The operators used in GWB guarantee topological and a wide class of geometric validity constraints for the solid. upon Euler operators, sweep operators and parametrized shapes have been implemented. Representations may be stored into a data base in a procedural format. Based on the model, line figures may be drawn and volume properties of the solids may be calculated. GWB is based on a general infrastructure (workbench) approach of system construction. The beneficiance of this approach is demonstrated.
CAPITOL : A LOW COST 3-D MODELLING AND VISUALIZATION SYSTEM FOR INTERIOR DESIGNERS AND ARCHITECTS
(The Eurographics Association, 1981) Webster, C. A. G.; J. L. Encarnacao
The CAPITOL system aims to provide a flexible but low cost 3-D modelling and visualization system which can be used as an integral part of the creative aesthetic and visual design process by interior designers and architects. Speed and scene complexity trade offs within the confines of a small personal computer resulting in only wire frame images being provided but otherwise the range of facilities offered is quite comprehensive.
A Revolution in Hardware Systems Design and its Implications for the Graphics Community
(The Eurographics Association, 1981) Clark, James H.; J. L. Encarnacao
APPLICATION OF GINO-F TO USE DISPLAY FILE TECHNIQUES ON RASTER SCAN DISPLAYS
(The Eurographics Association, 1981) Bramer, B; Sutcliffe, D C; J. L. Encarnacao
Raster scan displays are now available at lower costs than vector refresh displays. While many offer more facilities such as fill area and colour or greyscale capabilities, few offer a display file facility. It is desirable to use raster scan displays from line drawing graphics packages with support for devices with display files and so a project was undertaken to use an external display file with raster scan displays. A special device driver was written, for the GINO-F graphics package, with facilities for picture segmentation, segment identification using light pen simulation and picture segment manipulation.
EXPERIENCES IN THE DESIGN AND SUPPORT OF A GRAPHICS DEVICE DRIVER INTERFACE
(The Eurographics Association, 1981) Reed, Theodore N.; J. L. Encarnacao
The Common Graphics System (CGS) was developed at the Los Alamos National Laboratory. A standard device driver interface was defined for graphics device drivers and for use by user-callable graphics subroutine packages. This paper describes the existing CGS device driver interface, the experience we gained using it, and the extended interface capable of supporting more powerful graphics devices. The relationship between this interface and the CGS Metafile is also discussed.
SMOOTHING A DIGITIZED CURVE BY DATA REDUCTION METHODS
(The Eurographics Association, 1981) Opheim, Harald; J. L. Encarnacao
In order to reduce storage and subsequent processing costs for a digitized cartographic curve, we may wish to reduce the data set. The data reduction method which is described in this paper, can be used on-line during the digitizing as well as afterwards on the total data set. We only wish to retain the salient points, and thus data reduction can be regarded as a tool for smoothing a curve. The paper also describes another way of smoothing, based on signal theory.
TOWN PLANNING AIDED BY AN INTEGRATED MUNICIPAL LAND INFORMATION SYSTEM
(The Eurographics Association, 1981) Eloranta, Kirsi; J. L. Encarnacao
The purpose of this paper is to describe the results of our recent land information systems research in The Institute of Geodesy at Helsinki University of Technology. Our goal is to make research on municipal systems by building pilot systems and also by studying technical implementation problems on theoretic basis. In this paper one of our pilot systems is described, the one that is designed for town planning applications. Generally the research project could be characterized by the following keywords: use of minicomputers, problem oriented approach, evolutive approach in systems design, applications oriented data base management and integration of urban land information systems.
Computer Graphics for Federal Planning in West-Germany
(The Eurographics Association, 1981) Rase, Wolf D.; J. L. Encarnacao
To satisfy the cartographic requirements for spatial analysis, planning and forecast on the federal level in West Germany the Federal Research Institute for Regional Geography and Regional Planning established a system for computer-assisted production of thematic maps. Development priority was given to choropleth and graduated symbol maps as the most important mapping techniques to display spatial disparities. Other, less frequently used techniques, e. g. network display, surface representation, perspective drawings, etc., have also been implemented to provide additional aids for visualization, and to reduce the bottlenecks in the manual production process.
THE IMPACT OF COMPUTER GRAPHICS ON INDUSTRIAL PRODUCT DEVELOPMENT
(The Eurographics Association, 1981) Vlietstra, J.; J. L. Encarnacao
SOME USEFUL BUT RATHER UNUSUAL GRAPHICAL PRIMITIVES
(The Eurographics Association, 1981) Magnenat-Thalmann, Nadia; Thalmann, Daniel; Bergeron, Philippe; J. L. Encarnacao
The MIRALIB library is a powerful graphical library which may be used with MIRA-2D, a graphical PASCAL extension as well as with the standard PASCAL language. MIRALIB includes figure algebra routines, figure measure functions, figure recognition predicates, image transformations as fitting or clearing and animation primitives. The most unusual primitives are presented with the help of a few examples.
AUTOMATIC GENERATION OF A CUBIC B-SPLINE REPRESENTATION FOR A GENERAL DIGITIZED CURVE
(The Eurographics Association, 1981) Lozover, O.; Preiss, K.; J. L. Encarnacao
Cubic B-splines are often used to represent curves and are usually specified by a process of interaction on a graphic screen between the designer and the computer. This paper describes a program which, when given a digitized curve of general shape, without a direct analytical representation, automatically finds suitable knot points and defines the cubic B-spline polygon corresponding to that curve. That B-spline polygon is used to regenerate the curve graphically. The method is generally applicable in many fields including computer aided design where a need exists to represent arbitrary curves with given accuracy. In this paper results applied to archeological vessels are shown, with a discussion of accuracy and compactness of the representation. The algorithm will accurately represent a curve, using less than 10% of the storage required if all the digitized points of the curve were stored.
TIME AND SPACE BOUNDS FOR HIDDEN LINE AND HIDDEN SURFACE ALGORITHMS
(The Eurographics Association, 1981) Schmitt, Alfred; J. L. Encarnacao
Asymptotic worst case time bounds for three hidden line algorithms are derived and analysed. The first algorithm is a brute force solution that needs at least quadratic time. The second exact hidden line algorithm is based on a classical divide and conquer strategy similar to Warnock's algorithm and the third one is completely new and uses a plane sweep. The last two algorithms need time between O(n log n) and O(n²log n) depending on properties of the class of 3D scenes used. A variant of the divide and conquer algorithm processes a suitable class of 3D scenes in linear time. These results clearly demonstrate, that the asymptotic time needed to eliminate hidden lines depends almost exclusively on properties of the scene and not so much on the cleverness of the algorithm.
THE HIGH-LEVEL GRAPHICS PROGRAMMING LANGUAGE PASCAL/GRAPH
(The Eurographics Association, 1981) W.Barth,; J.Dirnberger,; W.Purgathofer,; J. L. Encarnacao
A high-level programming language like PASCAL offers data types, variables, constants and operators, by which the programmer can reflect the actual world as a model inside the computer. The world of numbers and text has been represented in the computer for many years by various kinds of variables. The importance of computer graphics increases amazingly fast. But the developement of high-level programming languages, which include standard constructs for processing graphical informations, is far from where it could be. A good system should provide intelligible constructs, easy to learn and similar to usual programming, so that the programmer can fully concentrate upon the design of his pictures. For these purposes PASCAL/Graph*) was designed and implemented.
A NEW METHOD FOR LOCAL SMOOTH INTERPOLATION
(The Eurographics Association, 1981) Renner, Gabor; Pochop, Vladimir; J. L. Encarnacao
A new method for interpolation is presented which starts from a given set of data pints. The resulting curve consisting of a set of polynomials has tangent vector continuity in the nodes, and can have straight line sections incorporated in it, with preserved continuity properties. The interpolation is local in the sense, that the shape of the curve at a certain data pint is influenced by five data points in its neighbourhood. First the construction of tangent vectors, then the determination Of the parameter intervals are dealt with. These are selected in such a way that a quasi-natural parametrization is held along the whole curve.

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