EG1981 Proceedings (Technical Papers)

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ABSTRACT DATA TYPE BASED PROGRAMMING STYLE AND COMPUTER GRAPHICS
(The Eurographics Association, 1981) Giloi, W. K.; J. L. Encarnacao
The next generation of "intelligent" industrial robots will necessitate off-line programming systems in which generative graphics (picture generation) and cognitive graphics (picture understanding) is combined. This will require programming languages that comprise graphical data types. The classical implementation of a graphical programming system in the form of a procedure package deals with representations of graphical objects and thus does not provide graphical data types. However, modern abstract data type based languages allow graphical data types to be introduced as user-defined abstract data types. The features of such a language, CLU, is discussed, and the implementation of a graphical data type in CLU is illustrated by a simple example.
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.
AN APPROACH TO A CALCULATION-MINIMIZED HIDDEN LINE ALGORITHM
(The Eurographics Association, 1981) Hornung, Christoph; J. L. Encarnacao
Hidden line algorithms based on picture primitives only cannot recognize the areas of a picture completely visible or invisible. By testing each primitive of these areas they produce an overhead of calculations. Moreover they waste time by calculating the hidden lines explicitely and outputting the remaining edges. This paper describes a method which rather computes the visible parts of a picture than excludes the invisible ones. Furtheron an approach to recognize complete visible areas instead of single visible edges is made. A comparison with other techniques shows the qualitatively better computation time.
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.
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.
COMPUTER AIDED DESIGN LANGUAGE 'CADLAN'
(The Eurographics Association, 1981) Bigelmaier, Anton; Brunner, Helmut; Strack, Helmut; J. L. Encarnacao
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.
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.
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.
FAST INTERACTIVE GRAPHIC ANALYSIS AND PRESENTATION OF IRREGULARLY SPACED LATA z(x,y)
(The Eurographics Association, 1981) Hartwig, R. R.; J. L. Encarnacao
This is a method to be applied in R&D. 1. A surface is generated, containing exactly all given points z(x,y). 2. The degree of accuracy is gradually specified. One can swap 'ACCURACY for SPEED'. 3. 'Out of the picture' iso-lines, z-values, gradients, curves, curved cuts, etc. are specified interactively, and drawn, and 'converted into numerical data'. 4. Such data can be used for calculations, or for further presentations, etc... VISUAL VALUATION' and NUMERICAL CALCULATION are compound in a tool for 'cyclic' interactive analysis.
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.
A GKS IMPLEMENTATION FOR METEOROLOGICAL APPLICATIONS
(The Eurographics Association, 1981) Ducrot, A.; Lemaire, A.; Watkins, H.; J. L. Encarnacao
In this paper we describe a GKS implementation made at ECMWF and we point out some problems encountered related to the definition of GKS 6.2 and to the necessity to adapt to the meteorogical applications.
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.
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.
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.
THE IMPACT OF COMPUTER GRAPHICS ON INDUSTRIAL PRODUCT DEVELOPMENT
(The Eurographics Association, 1981) Vlietstra, J.; J. L. Encarnacao
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.
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.
A Revolution in Hardware Systems Design and its Implications for the Graphics Community
(The Eurographics Association, 1981) Clark, James H.; J. L. Encarnacao

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