Volume 04 (1985)

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    3D Icons and Architectural CAD
    (Blackwell Publishing Ltd and the Eurographics Association, 1985) Aish, Robert
    3D computer input has been a recurring challenge to engineers developing effective CAD systems. The approach adopted in this paper attempts to address a specific type of 3D input which is applicable to architecture and some engineering design tasks. In these processes, the object being designed is often an assembly of defined components. In a conventional graphics based CAD system these components are usually represented by graphical Icons which are displayed on the graphics screen and are arranged by the user. The system described here consists of 3D modelling elements which the user physically assembles to form his design. Each modelling element contains an element processor consisting of a machine readable label, data paths and control logic. The CAD system interrogates the elements. The logic within the element processors and the data paths are then used to interrogate other adjacent elements in the model. This system can therefore be considered as a "user generated""machine readable" modelling system. In an architectural application this provides the user with a system of 3D Icons with which to model and evaluate the built environment.
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    Affiliation Agreement
    (Blackwell Publishing Ltd and the Eurographics Association, 1985)
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    AFFILIATION AGREEMENT
    (Blackwell Publishing Ltd and the Eurographics Association, 1985)
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    APEX and STRETCH: A Practical Form for the Conic Arc
    (Blackwell Publishing Ltd and the Eurographics Association, 1985) Gossling, T.H.; Stokes, S.T.S
    This paper presents formulae and results from a practical implementation of a conic arc specified in terms of its end-points and other descriptors, based on the three numeric factors, bulge, shear and squash, described in an earlier paper. The parametric form for the derivative is given, from which are found the normals from a given point to the arc, and formulae for splitting off one or more parts from it. A method of chordal approximation for plotting purposes is also presented, and the effects of applying transformations are discussed.
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    An Application of Geodesic Curves to Sail Design
    (Blackwell Publishing Ltd and the Eurographics Association, 1985) Haw, R.J.
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    Arbitrary Area Filling in a Fast Procedure
    (Blackwell Publishing Ltd and the Eurographics Association, 1985) Ying, Dao-Ning; Feng, Xing
    A representation for area filling is described which allows shading of an area that may have both straight lines and circular arc edges and include holes within its boundaries. For efficiency an elimination algorithm which has a waiting line list and a currently active line list is adopted. For calculating intersections, a more time saving method is used. The algorithm and some practical examples are discussed. The main features of the algorithm are execution with high speed and less storage requirement. The program is written both in BASIC and FORTRAN 77 and could be executed on a microcomputer such as APPLE II, IBM-P/C etc. The sample outputs shown in this paper are generated by the APPLE II with high efficiency.
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    Better Understanding through Formal Specification
    (Blackwell Publishing Ltd and the Eurographics Association, 1985) Duce, D. A.; Fielding, E. V. C.
    The Graphical Kernel System (GKS) is now registered as an ISO International Standard for computer graphics programming. One of the major innovations of the Standard is the bundled specification of aspects, a mechanism which gives the applications programmer the ability to tailor the appearance of a picture independently on each of the workstations on which it is displayed, using the capabilities of the workstations. GKS also incorporates the traditional method of individual specification of aspects in which each workstation does the best it can to represent global aspect values. In this paper a formal specification technique, the Vienna Development Method (VDM), is used to describe aspect specification. The GKS model of aspect specification is progressively constructed from simpler models. Properties of these simpler models are formulated and the specifications are proved to conform to these. The properties are then traced through the more complex models. The paper demonstrates the applicability of formal specification to the design of graphics software and the ability of formal techniques to catalyse the deeper understanding of designs.
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    Bias Compensation for Photon Maps
    (Blackwell Publishing, Inc and Eurographics Association, 1985) Enderle, Guenter; Arnold, David
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    Book Review
    (Blackwell Publishing Ltd and the Eurographics Association, 1985) Oliver, Martin
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    Book Reviews
    (Blackwell Publishing Ltd and the Eurographics Association, 1985)
    A Programmer’s Geometry by A. Bowyer and J. Woodwark.Computer Aided Design: Fundamentals and System Architecture by J. Encaracao and E.G. Schlechtendahl.
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    Browsing High Definition Colour Pictures
    (Blackwell Publishing Ltd and the Eurographics Association, 1985) Willis, Philip; Milford, David
    The authors describe a method of presenting colour pictures which allows users to browse by panning and zooming. The pictures are seen as though on a 512 by 512 by 12 bit framestore, but are defined to 4096 by 4096. The implementation allows the entire picture to be seen in overview, with fine details averaged, or to be zoomed in upon with finer detail progressively revealed by a sequence of twofold linear magnifications. Further zooming, beyond the resolution of the picture data, automatically produces a conventional pixel replication effect. In addition, the picture may be panned vertically or horizontally.
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    Calendar of Events
    (Blackwell Publishing Ltd and the Eurographics Association, 1985)
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    Calendar of Events
    (Blackwell Publishing Ltd and the Eurographics Association, 1985)
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    Calendar of Events
    (Blackwell Publishing Ltd and the Eurographics Association, 1985)
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    Calendar of Events
    (Blackwell Publishing Ltd and the Eurographics Association, 1985)
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    Colour Graphics-Blessing or Ballyhoo?
    (Blackwell Publishing Ltd and the Eurographics Association, 1985) Murch, Gerald M.
    The human visual system-s capacity and capability to process colour can be applied as a design criterion for colour information displays. This paper reviews key elements in the visual domain of colour, encompassing the visual, perceptual, and cognitive modes and develops a series of recommendations for effective colour usage based on these elements.
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    A Compressed Data Structure for Surface Representation
    (Blackwell Publishing Ltd and the Eurographics Association, 1985) Cottingham, Marion S.
    One of the standard methods of simplifying the task of obtaining a shaded image of a solid object is to represent it by a polyhedron. Another method is to use sculptured surface modelling which represents surfaces by collections of surface patches. Using either method the surfaces can be approximated by facets, which are simple to shade according to photometry information.To obtain a smooth image in regions of high curvature, the surface would typically be required to have hundreds or thousands of facets. Because of the large number of facets involved, it is extremely important that geometrical and topological information is stored in an efficient manner. This information must include all that is required for an unambiguous representation of the solid(s) in question.The compressed data structure (CDS) is suitable for this purpose, and is capable of defining the majority of surfaces. The structure is intended to minimise the amount of data stored, with as much information as possible being implied. The CDS can be easily generated knowing the order of the vertices defining the surface.
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    Computer Animation and Art Slide Competition
    (Blackwell Publishing Ltd and the Eurographics Association, 1985) Rambert, Patrick
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    Computers and Art
    (Blackwell Publishing Ltd and the Eurographics Association, 1985) Smith, B Reffin
    The use of computers in art is not new: examples are given of past and present applications. Three categories are mentioned: computer as tool, as origin of concepts and metaphors, and as controller. The use of the computer in art gives rise to the idea of computing as representation- rather than just information-processing. Thus the computer can be said to 'belong' to artists and designers, and can be seen as a qualitative device. It is argued that computing is 'really' an art or design activity, and that this has implications for art, design and computing.
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    Concerning the Specification of User Interfaces
    (Blackwell Publishing Ltd and the Eurographics Association, 1985) Duce, D. A.