EG1986

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    A Quad-Tree Algorithm for Displaying a 2-Dimensional Slice of an N-Dimensional Weighted Voronoi Tessellation
    (The Eurographics Association, 1986) Angell, Ian O.; Moore, Richard E.M.; A.A.G. Requicha
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    Methods for Cross-Sectional Design of B-Spline Surfaces
    (The Eurographics Association, 1986) Woodward, Charles D.; A.A.G. Requicha
    The complexity of free-form surface construction and interaction can often be reduced with methods of crosssectional design. A number of such methods, includin sweeps, skinning and surface interpolation are described in this paper for the B-spline surfaces. The methods are demonstrated with examples using the CUBES subroutine package.
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    An Adaptive Graphics Interface for Effective Visual Representation
    (The Eurographics Association, 1986) Holynski, Marek; Garneau, Robert; Lewis, Elaine; A.A.G. Requicha
    This paper presents a progression of experimental work aimed at incorporating principles of graphic presentation and preferences of users into a computer graphics system. These standard-s for effective visual representation of data are based on empirically developed criteria. Several different approaches for obtaining these criteria from picture attributes are described. First, relevant attributes are verified using a series of pictures created with a menu-driven program. Then representation criteria are developed by an automatic rule acquisition program in the form of condition-action rules. These rules can be utilized by an adaptive graphics system that can generate, change and refine images interactively. Practical applications are suggested.
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    The Integrated Display Controller (IDC) for VLSI-Design Workstations
    (The Eurographics Association, 1986) Strk, Jrgen; A.A.G. Requicha
    A display controller to accelerate the updating of the frame buffer in raster displays is presented. The advantage of a frame buffer system is the ability to display pictures of any complexity, flicker free. The disadvantage is the great amount of pixel data, which must be updated, when the picture is changed. The Integrated Display Controller (IDC) described in this paper gets its name from the fact, that both a pixel plane and a processor are integrated on a single chip. An internal logical unit, a shifter and special memory are provided to process complete rows and columns of pixels, or some part of them in parallel All operations are performed in one bus cycle, which means that all the pixels addressed in the row or column are modified at the same time. Due to the special organization of the IDC, time consuming operations like block transfer or scrolling can be done significantly faster than in conventional systems. An experimental IDC with a lower screen resolution is developed to demonstrate the feasibility of the design. It is intended for use in VLSI-design workstations, where a great quantity of data has to be manipulated.
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    Memory Organization for a Cubic Frame Buffer
    (The Eurographics Association, 1986) Kaufman, Arie; A.A.G. Requicha
    A special memory organization of a cubic voxel-based frame buffer is presented. The memory of voxels is divided into n modules of voxels each. The k-th module groups together all the principal diagonal planes within the cubic frame buffer, that their sequential index is k mod (n ). This organization guarantees that all the n voxels which constitute a row in any direction parallel to the axes reside in different modules, permitting the retrieval of all the voxels of a row simultaneously. This memory layout is the heart of a voxel-based CUBE Architecture for three-dimensional graphics. The architecture employs three processors which access the memory, to input, manipulate, and view the image within the memory. The unique memory organization enables these processors and the entire system to cope with real-time constraints.
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    Deformations of Sweep Objects in Solid Modelling
    (The Eurographics Association, 1986) Post, Frits H.; Klok, Fopke; A.A.G. Requicha
    Deformations, such as bending, twisting and tapering, are important operations for modifying the shape of solid objects. In this paper, we present methods to deform objects defined by sweeping. A closed 2D polygon (the contour) moves along a 3D polyline (the trajectory), thus producing a polygonal approximation of a generalized cylinder. During sweeping, the contour can be incrementally scaled and rotated, resulting in tapered and twisted objects. Also, smoothly bent objects can be produced by performing local rounding operations on trajectories. The methods have been implemented in the solid modeller PLAMO, in which the deformed sweep objects can be used, as well as other types of bodies, as primitives in a CSG tree.
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    A Multiprocessor Architecture For High-Quality Interactive Displays
    (The Eurographics Association, 1986) Sutherland, Robert J.; A.A.G. Requicha
    A multiprocessor array coupled to a deep framebuffer is proposed as the basis for an interactive user environment of high quality. Several aspects of such an architecture are considered, improvements on previous approaches are suggested, and two designs of high-performance displays based on standard LSI components are described.
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    A Pixel-Parallelhidden Surface Algorithm For Constructive Solid Geometry
    (The Eurographics Association, 1986) Jansen, Frederik W.; A.A.G. Requicha
    VLSI techniques have greatly enlarged the possibilities to design new frame buffer architectures with parallel processing capabilities down to the pixel level. For these pixel processor systems a parallel hidden surface algorithm is presented for displaying objects defined with Constructive Solid Geometry. The algorithm is based on a CSG evaluation with bitwise operations and multiple scanning of the primitives.
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    A Multiple Application Graphics Integrated Circuit - MAGIC
    (The Eurographics Association, 1986) Agate, M.; Finch, H.R.; Garel, A.A.; Grimsdale, R.L.; Simmonds, A.C.; Lister, P. F.; A.A.G. Requicha
    MAGIC is a geometry processor which Corms a part of a graphics system based on parallel processing. The number of MAGIC processors required is dictated by the desired system performance. Each unit is capable of controlling the transformation of points and edges from the co-ordinate system of the world model into screen co-ordinates, and performing the associated clipping operations. The proposed VLSI implementation of these transformations is intended to be sufficiently flexible for additional operations such as texture mapping and ray tracing to be supported.
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    A consistent algorithm to fill triangles and triangular patches
    (The Eurographics Association, 1986) Overveld, C.W.A.M. van; Lierop, M.L.P van; A.A.G. Requicha
    In this paper an algorithm is described for filling triangles in 3D. Since this algorithm uses integer arithmetic only, it is not hampered by inconsistencies that normally arise due to finite machine precision. Moreover, the same algorithm is used for both curved and flat triangular patches.
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    A Visualisation Tool for (Landscape) Architects
    (The Eurographics Association, 1986) Lankhorst, Mrs. J. Roos - Klein; A.A.G. Requicha
    In a small and crowded country such as the Netherlands both the government and the individual people are very concerned with what is happening in their environment. Apart from the ecological impacts, the visual effects of new developments are often a very important issue. In this respect a realistic visualisation of future developments can be very useful. Described here is the product of the first stage of a research programme aimed at providing visualistion aids for landcape architects and building designers. Besides showing future developments to the people involved, this tool should enable the building designer to evaluate the aesthetics of a design with respect to the surroundings. Moreover it should enable the landscape architect to "reshape" the landscape by adding, removing and editing artifacts and natural elements on the the graphics screen.
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    A Portable Graphical Display System For The Partially Sighted
    (The Eurographics Association, 1986) DUNLOP, G.R.; B.Sc.,; B.E.(Hons),; Ph.D.,; M.I.E.E.,; C.Elec.Eng.,; A.A.G. Requicha
    A portable reading aid based on a graphical display system has been developed for partially sighted persons. This graphical display system incorporates dual microprocessor control of a flat panel AC plasma display and a solid state fibre optics camera. The unique camera uses coherent fibre optics for image dissection so that a synthetic viewing aperture is generated from a single linear imaging device. The lensless camera utilises proximity focusing and switchable electronic magnification settings from 4 to 64. The graphical display produces neon orange images which are refreshed at almost 100 Hz to give bright flicker free images which are suitable for viewing either directly or with only the peripheral vision available to many partially sighted people.
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    Towards the Construction of Graphical Interfaces on the Basis of Geometric Models
    (The Eurographics Association, 1986) Prospero, Manuel Joao; Messina, Luiz Ary; A.A.G. Requicha
    Dialogue control and dialogue object structures are the outlined concepts developed in this paper. Phases of a CAD-Process are presented to show an outstanding application for the concepts The use of logic programming dealing with geometric structures performs the innovative elements to enable the construction of more flexible graphical interfaces, which can operate as information collectors and structure checks in design processes.
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    An Implementation of the GKS-3D/Phigs Viewing Pipeline
    (The Eurographics Association, 1986) Singleton, Karen; A.A.G. Requicha
    Following the establishment of GKS as the first international standard for computer graphics, two new standards, GKS-3D and PHIGS, are emerging which cater for three dimensional graphics. In order to display a 3-D object, a description of how it is to be viewed must be given. GKS-3D and PHIGS provide a viewing pipeline to generate the parallel or perspective view required. This paper describes in detail the functionality and an implementation of the GKS-3D/PHIGS viewing pipeline.
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    A Statistical Method For Adaptive Stochastic Sampling
    (The Eurographics Association, 1986) Purgathofer, Werner; A.A.G. Requicha
    Stochastic sampling is a good alternative to pure oversampling in terms of image quality. A method for adaptively controlling the number of required samples to the complexity of the picture is presented. The quality of the obtained picture can be controlled by two well-understandable parameters, these parameters define an error interval sire and the probability that a pixel lies within it. The usefulness of the method is described by applying it to distributed ray-tracing.
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    A General Purpose User Interface With Hierarchical Data Structure Management
    (The Eurographics Association, 1986) Janni, Alberto Di; Italiano, Margherita; A.A.G. Requicha
    This paper presents a general purpose User Interface Management System based upon a user driven menu handling and a hierarchical organization of graphic data structure. The package has mainly two purposes: one being to provide facilities to the application programmer in order to ease their tasks and the other one bei to provide a uniform enviroment to the final user. It fulfills two different tasks: it realizes the dialogue with the user and offers a complete set of high level procedures to manage graphic data. lauded attributes, like device independence, feedback at both syntactic and semantic levels, internal automatic recovery, style independent interface toward the application, management and hierarchical definition of structured graphic output, high level graphic functions and a simple definition language. Moreover this system is particularly intended to cover requirements of tools dedicated to integrated circuit design and makes use of a few devices to cut off the computation time and to optimize the memory occupation.
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    An Advanced Display System With Natural Interactivity
    (The Eurographics Association, 1986) Kankaanp, Arto; A.A.G. Requicha
    This paper describes an experimental display system that allows easy interaction with the graphics display. The user uses a pen-like device to draw directly on the display surface. The system is based on an electroluminescent flat panel with a resistive touch-sensitive surface. A pen with a conductive tip is used for direct drawing. For evaluation the display system is connected to a powerful microcomputer having a true bit-mapped graphics capability. The prototype software consists of a word processing program that includes integrated line graphics drawing capability. Text correction and formatting is done directly on the display using standard proof correction marks. Graphics drawing is done by sketching a figure on the screen with the pen and correcting it by software. The system is also evaluated using the Keystroke-Level Model by CARD et. al. [1] for accomplishing the basic editing tasks with a word processing application.
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    Mappings Between Product Data Definitions
    (The Eurographics Association, 1986) Richter, Dieter; A.A.G. Requicha
    It can be observed that existing product data interfaces are constructed by a pragmatic manner. It is not seen any theoretical approach neither for describing nor for evaluating models. In this paper an algebraic approach based on heterogeneous algebras is presented.
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    A Version Management System for Design Environments
    (The Eurographics Association, 1986) Heine, Thomas Riedel-; Köhler, Dagmar; A.A.G. Requicha
    Design environments for CAD/CAM require new techniques of version management. This work presents a concept of a largely data modelindependent version manager thus allowing easy integration into any existing database system. An implementation proposal of a version manager based on a relational database system is given.
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    Digital Synthesis Of Calligraphic Script
    (The Eurographics Association, 1986) Dooijes, E.H.; A.A.G. Requicha
    We discuss some of the problems associated with the generation of publication quality, quasi-calligraphic script from keyboard input. Our ultimate goal is the construction of a system for the production of Arabic texts, to be implemented on a microcomputer.