EG1983 Proceedings (Technical Papers)

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    Fast Previewing Techniques in Raster Graphics
    (The Eurographics Association, 1983) Jansen, F.W.; Wijk, J.J. van; P.J.W. ten Hagen
    The long processing times inherent in the use of raster graphics techniques for the shading of complex scenes, complicate the design and debugging of a picture. The efficiency of the picture-generating process can, however, be improved by adding several interactive facilities to the system. In particular, fast previewing techniques are valuable for checking the modeling and for getting a good impression in an early stage of the picture-definition process. A discussion of raster graphics system design is followed by examples of fast pre-viewing techniques for the shading and texture mapping of surface models and for the shading of solid models using a raycasting technique.
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    A Delaunay-Based Method for Surface Approximation
    (The Eurographics Association, 1983) Floriani, L.De; Falcidieno, B.; C.Pienovi,; P.J.W. ten Hagen
    This paper describes a method for constructing a surface representation model from a given set of data points.A Triangulated Irregular. Network has been chosen as data structure, thus representing the surface as a set of contiguous non -overlapping and irregurarly shaped triangular facets.The proposed method makes use of a Delaunay triangular grid adapted to non-convex domains. Using only representative subsets of the given set of points, the method allows the construction of approximating surfaces which rest within a predefined tolerance.
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    GKS-300 - PASCAL Implementation of the Graphical Kernel System (GKS) on a Minicomputer Based Graphical Workstation
    (The Eurographics Association, 1983) Schmitgen, Günther; P.J.W. ten Hagen
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    Non-Rectangular Surface Patches Suitable for Inclusion in a B-Spline Surface
    (The Eurographics Association, 1983) Sabin, M.A.; P.J.W. ten Hagen
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    Closed 2D Contour Algorithms for 3D Reconstruction
    (The Eurographics Association, 1983) Huijsmans, D. P.; P.J.W. ten Hagen
    In collaboration with the department of Anatomy a software package (FORTRAN 77) for 3D reconstruction of anatomical material is under development. Input material consists of a series of planparallel slices of an embedded specimen. 3D reconstruction of volume segments with closed 3D surface boundaries is achieved by taking closed 2D contour boundaries within each intersecting plane.
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    Syntactic Methods in Computer Graphics
    (The Eurographics Association, 1983) Slavik, P.; P.J.W. ten Hagen
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    Refinement of the Stress Contour Plots by the Local Interpolations, Extrapolations ans Averaging
    (The Eurographics Association, 1983) Draskovic, Z.; Berkovic, M.; P.J.W. ten Hagen
    The purpose of this paper is an attempt to improve the stress contour plots for the simplest two-dimensional finite elements. The proposed approach is achieved by the use of the simple local interpolations, extrapolations and averaging of the existing stress analysis results. The usual and the proposed, refined procedure are compared for two typical examples.
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    Interactive Graphical Planning
    (The Eurographics Association, 1983) Jackson, Michael J.; Clark, Tony; P.J.W. ten Hagen
    Accurate planning is an essential part of efficient project management, but computer-aided techniques have, in the past, not fulfilled their potential in this important field, This paper describes how interactive graphics techniques have been used to help the planner in the design of his programme of work and in the dissemination of his recommended plan.
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    The GHOST-80 Colour Raster Extensions
    (The Eurographics Association, 1983) Prior, W.A.J.; Sutherland, R.J.; P.J.W. ten Hagen
    The GHOST Graphical Output System has been developed over a long period. The most recent version, GHOST-80 has been enhanced with routines for colour raster displays. The integration of these routines with the existing package is described and their ease of use is emphasised.
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    On Developing a GKS Driver Architecture for Raster Workstations
    (The Eurographics Association, 1983) Rix, Joachim; P.J.W. ten Hagen
    The use of raster graphics devices needs adapting to graphics applications. The first graphics standard, the Graphics Kernel System GKS, defines a logical interface on an application and device independent level. The workstation driver maps the logical GKS functions to device functions. First some special raster device facilities are outlined and then it is shown how to use them within the driver. To reduce the amount of driver implementations a common driver concept is sought here, especially for raster devices.
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    Fast Access to Archival Information Stored on Optical Memory Discs
    (The Eurographics Association, 1983) Bittner, H.; Krömker, D.; Lenzer, R.; Olsowski, H.D.; P.J.W. ten Hagen
    A database processor based on a multi-microprocessor system managing archival data was developed for the use in local area networks. To grant fast and easy access from office workstations to heterogeneous information stored on optical memory discs, a new strategy of storing data and handling user requests was designed.
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    High Level Language Support for 3-Dimensional Graphics
    (The Eurographics Association, 1983) Duhovnik, Joze; Kimura, Fumihiko; Sata, Toshio; P.J.W. ten Hagen
    In the paper the design process is analysed and a new model of the design process which is usefull in CAD is explained. At working a construction with the computer we have to consider the function and form. The function defines the capacity of the construction and the usefulness dependet on the connection machine-nature. With the form we define the possibility of manufacturing and usefulness dependet on the connection man-machine, For a successful working of the function and the form we use geometrical modelling and word processing, The interaction between man-computer can the most easily be done with sketching (form) and speech (words). In the paper the data input with sketching is explained using keyboard instead of speech. In the appendix an example of working the construction by our method is presented.
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    A Geometric Data Manager
    (The Eurographics Association, 1983) Tikkanen, M.; Mantyla, M.; Tamminen, M.; P.J.W. ten Hagen
    GWB/DMS is the data management subsystem of GWB, the Geometric Work-Bench. I t has been designed specifically for three-dimensional computeraided design applications. As the data definition and manipulation take place with extensions of high-level language constructs, GWB/DMS offers a direct migration from an independent "in-core" application to one using a database. Besides, the user can define additional access paths using geometric or conventional indices. The interactive nature of design is taken into account by including a simple transaction control mechanism. Transparency in ordinary programming and efficiency are the main design criteria of GWB/DMS. Its novelties are: 1) geometric indices facilitating access by location, 2) address calculation as the main access method and 3) tools for controlling the "physical closeness" of database objects.
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    XGKS - A Multitask Implementation of GKS
    (The Eurographics Association, 1983) Herman, I.; T.Tolnay-Knefely,; Vincze, A.; P.J.W. ten Hagen
    A multitask design for GKS is presented, a realization aiming small computers and intelligent graphic hardware.
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    A High Level Interface to the Graphical Kernel System - GKS
    (The Eurographics Association, 1983) Watkins, H.K.; P.J.W. ten Hagen
    A Graphical Package is described with particular reference to the petroleum industry. One of its design aims is that it should act as a user interface to GKS and be as user friendly as possible. As a further design aim, it has to be capable of implementation as a stand-alone graphics package in situations where GKS is not. available. The implications of these design aims are outlined.
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    Towards GKS Binding to PASCAL
    (The Eurographics Association, 1983) Antoy, Sergio; Dettori, Giuliana; P.J.W. ten Hagen
    When binding GKS to the Pascal programming language some problems arise which are not trivial, Problems related to the use of a library, to the passing of array parameters to procedures and to the definition of suitable types for GKS data must be carefully discussed, since each of these does not have a unique solution, A proposal for solving the above problems is presented in this paper.
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    Computer Graphic Presentation of Road Data
    (The Eurographics Association, 1983) Koren, Hans; Holbaek-Hanssen, Erik; Tjugen, Olav H.; Wiborg, Trond; P.J.W. ten Hagen
    This paper presents a system for plotting traffic accidents and other data related to roads, on computer drawn maps. A method for simultaneous presentation of many different aspects of the road is also described.
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    Depth Sorting by Windowing
    (The Eurographics Association, 1983) Gangnet, Michel; P.J.W. ten Hagen
    In this paper we present the first version of a new algorithm for hidden-surface and hidden-line elimination which applies primarily to the generation of indoor perspective views of simple building models. The algorithm is very efficient and though being an object space algorithm its run-time depends only on the complexity of the generated picture. The algorithm is recursive and uses extensively the coherence given by the adjacencies of the rooms within a building. Extensions to more complex models are considered.
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    Standard Graphics as a Geometric Modelling Device
    (The Eurographics Association, 1983) Takala, T.; P.J.W. ten Hagen
    A view is taken on geometric modelling systems as abstract data types. Having this frame of reference, the Device Independent Segment Storage of standard graphics is considered, and found to possess useful capability of modelling. The unused potential can be benefit simply by adding a few new inquiry functions, which give the application program an access to the individual primitives stored in segments. Even more advantage can be got i f semantics other than just grouping of items can be assigned to the segments. For example, in 3D graphics, a group of polygons can be labeled to mean a solid. A flexible framework (AGX) is built for experiments, and the feasibility of the concepts presented here is demonstrated by practical applications.
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    Inverse Perspective Mapping in Scanline Order onto Non-Planar Quadrilaterals
    (The Eurographics Association, 1983) Hourcade, J.C.; Nicolas, A.; P.J.W. ten Hagen
    Mapping textures onto three dimensional objects should resolve two class of problem ; first find a correspondence between the texture and the displayed object, secondly filter the texture according the display grid and the texture grid. Our work presents a review of existing mapping techniques on polygons and patches, gives and evaluates an algorithm for mapping texture on quadrilaterals taking into account particular constraints of scanline order hidden surface algorithms.