EG1981 Proceedings (Technical Papers)

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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.
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.
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.
MOVIE.BYU - 1981
(The Eurographics Association, 1981) Christiansen, H. N.; Stephenson, M. B.; Nay, B. J.; Ervin, D. G.; Hales, R. F.; J. L. Encarnacao
MOVIE.BYU facilitates the display of three-dimensional mathematical, topological, and architectural models as line drawings or as continuous tone shaded images. This software provides the capability to clip and cap three dimensional systems: modify geometry, displacement, and/or scalar function files; generate new models or title representations; and convert contour line definitions into polygonal element mosaics. The 1981 edition features "bomb proof" free format input: enhanced clipping and capping of solids: routines for the description and display of functions of two variables: and new display options. A mini-computer version of the system, MINI-MOVIE.BYU, features a disk resident data base. A device driver for the Tektronix 4027 color graphics terminal is also available.
USER GUIDANCE IN INTERACTIVE SYSTEMS - THE ROLE OF GRAPHICAL FEATURES
(The Eurographics Association, 1981) Trispel, S.; Günther, K.; J. L. Encarnacao
Users of technical systems become increasingly involved in computer controlled dialogues of various forms. One kind of dialogue is of the interrogative form based on the exchange of alphanumeric and symbolic strings via keyboard terminal. Other kinds make use of more sophisticated information display modalities in combination with various data input modalities. Each configuration depends on the type of task and user. There is the expert user of a CAD system on one hand, and the non-expert user of a medical information system on the other. This paper investigates the requirements for non-expert menu dialogue design as it relates to the visual interface. The relevance of certain graphical features, based on the capabilities of today's graphics terminals, is discussed. It is concluded that the design of those interactive systems, which rely mostly on the visual interface, can and must extensively incorporate advanced graphical features in an intelligent manner. User guidance as an aspect of system intelligence can thereby be enhanced significantly.
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.
TELIDON: WHERE VIDEOTEX MEETS COMPUTER GRAPHICS
(The Eurographics Association, 1981) Newman, Hannah; J. L. Encarnacao
Videotex is a system by which information can be accessed from central data bases by the general public. By the use of a television receiver augmented by a micro-computer controlled interface device, a user can access pages of information over a communications medium. Telidon uses a coding method for the transmission of graphical and textual information which is device and communication channel independent. Pictures are encoded using geometric primitives called Picture Description Instructions. Standards for graphics metafiles are being developed. Cornpatibility of Telidon and computer graphics can be obtained by developing a graphics metafile in which the requirements for both are satisfied.
EXTRACTING LINE MAPS FROM IMAGES
(The Eurographics Association, 1981) Jimenez, Javier; Navalon, Jose L.; J. L. Encarnacao
We present methods to vectorize automatically information given in raster form, the algorithms used are discussed briefly, and results for some test cases are presented. The compression of information is discussed as well as some theoretical models.
COMPUTER AIDED DESIGN LANGUAGE 'CADLAN'
(The Eurographics Association, 1981) Bigelmaier, Anton; Brunner, Helmut; Strack, Helmut; J. L. Encarnacao

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