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Item GRAPHIC DISPLAYS IN THE COMPUTER AIDED DESIGN OF LIFT SYSTEMS(The Eurographics Association, 1982) Barney, G.C.; D.S. Greenaway and E.A. WarmanThe sizing of lift systems to meet passenger demands is normally carried out in a quantitative way by calculation. Nothing is done to determine the quality of service provided. This paper describes how a computer aided design suite using discrete simulation techniques coupled to extensive graphic displays overcomes these deficiencies.Item Faster Phong Shading via Angular Interpolation(Blackwell Publishing Ltd and the Eurographics Association, 1989) Kuijk, AAM.; Blake, E.H.One of the most successful algorithms that brought realism to the world of 3D image generation is Phong shading. It is an algorithm for smooth shading meshes of planar polygons used to represent curved surfaces. The level of realism and depth perception that can be obtained by Phong shading is attractive for 3D CAD applications and related areas. However, per pixel computation costs which were too high and/or artifacts, introduced by some of the more efficient evaluation methods and apparent only when displaying moving objects, are major factors mat blocked the common usage of Phong shading in highly interactive applications.In this paper we present angular interpolation for Phong shading planar polygons. Angular interpolation was a method especially designed to meet requirements as imposed by special purpose hardware we developed1, but turned out to be generally applicable. The angular interpolation method appears to be very efficient and reduces artifacts when displaying moving objects. Ideally a shading algorithm imposes no need for subdivision of patches as presented by the solid modelling system. Shading calculation via angular interpolation yields such an ideal algorithm. We will describe two alternative evaluation methods that trade off evaluation cost against level of accuracy. They both can handle light source and view point at arbitrary distances, but differ in level of accuracy. As a consequence these alternative evaluation methods do impose restrictions on the topology of patches and light sources. However, generally, the limitations imposed by these alternative shading methods are much more liberal than the limitations on patch size imposed by the geometry.The most economic evaluation method we present can incrementally compute the colour intensity along a scanline by two additions per pixel. The methods presented are generally applicable and can easily be implemented in hardware.Item Algorithm for Clipping Arbitrary Polygons(Blackwell Publishing Ltd and the Eurographics Association, 1989) Andreev, Rumen D.Item Free-Form Surfaces Modeling by Evolution Simulation(Eurographics Association, 1988) Lienhardt, PascalWe present in this paper a procedural method for modeling free-form, planar surfaces subdivisions, which allows simulating evolutions of such subdivisions. This method is founded on the common principles deduced from corpuscular phenomena modeling method (particle systems), and method for vegetal trees modeling by simulation of evolution. These principles are : - use of a discrete model, which is a set of basic elements, from which time discretization is deduced, -proper activity of basic elements; these methods consists in simulating the behaviour of these elements; - characterization of modelled object evolution, which is achieved by "functions" associated to basic elements; - priority of topology over geometry. A surface is defined as a set of surface elements, supported by a rooted, planar tree. A surface is initially reduced to a point. Surface evolution characterization and control are exclusively exerted through this tree. This method is applied to image synthesis and animation of natural shapes, especially vegetal shapes.Item Towards a Z-Buffer and Ray-Tracing Multimode System based on Parallel Architecture and VLSI chips(The Eurographics Association, 1986) P.Lemy,; W. StrasserAfter the hidden surfaces algorithms for 3D rastergraphics, hardware design isthe main problem, for many applicat ions, such as : Audiovisual animat ions. CADCAM,and simulation.After a short description of our CUBI 7 system (a 3D real-time Z-buffer system),and its CRISTAL module which increases RAY-TRACING computations, we present ourhardware project based on :-Parallel architecture for RAY-TRACING, special effects ; This module is alsouseful for pre-processing the image : (rotations, clipping, perspective transform... ).-A or Z-BUFFER which will be designed on VLSI chips polygon filling will be alsodesigned with pipe-lined chips."Item Computer Generation of Penrose Tilings(Blackwell Publishing Ltd and the Eurographics Association, 1988) Rangel-Mondragon, J.; Abas, S.J.Item Evaluation of Standard Graphics Packages(Blackwell Publishing Ltd and the Eurographics Association, 1987) Klok, FopkeIn order to compare the quality of different implementations of GKS, the ISO0 standard for computer graphics, an evaluation method for GKS implementations is presented. It is based upon several groups of criteria. One group of criteria is concerned with performance, by which we understand here the memory requirements and time requirements for programs using GKS functions. A program that measures the performance of GKS packages is presented. Results of this evaluation method with several commercially available GKS implementations are described in summary. A checklist for evaluation of standard graphics packages is added as an appendix.Item HUTWINDOWS: AN APPROACH TO USER INTERFACE DEVELOPMENT(The Eurographics Association, 1985) Koivunen, Marja-Riitta; Mntyl, Martti; C.E. VandoniThe design and implementation of good graphical user interfaces is a difficult task requiring good taste and proper tools. The HutWindows system under development at Helsinki University of Technology is intended to be an easy-to-use set of tools for implementing a graphical user interface to an application having a simple text-oriented interface. It provides a single input channel for interleaved input from a collection of non-overlapping windows, and output primitives for the display of text and graphics. All details of the user interface are effectively hidden from the application, and can be modified by the user without touching the application code.Item Ray Tracing Rational B-Spline Patches in VLSI(The Eurographics Association, 1987) Schneider, Bengt-Olaf; Fons Kuijk and Wolfgang StrasserRational B-spline surfaces make it possible to merge the concepts of freeform surfaces and that of surfaces described by rational polynomials especially conic sections. For ray tracing it is crucial to determine the intersection between ray and object. Therefore an algorithm is developed that is suitable for a VLSI implementation. Some alternatives for the implementation of this algorithm are presented and discussed. The paper concludes with a discussion of some problems and possible further developments.Item A Three-Dimensional Shaded Display Method for Voxel-Based Representation(The Eurographics Association, 1985) OHASHI, Toshiaki; UCHIKI, Tetsuya; TOKORO, Mario; C.E. VandoniIn this paper, methods for displaying solid objects represented by a three-dimensional array of voxels are described. The Linear Interpolating Projection Method is proposed as a method by which such objects can be projected onto the screen in perspective. In order to shade the projected images, the Depth only Shading Method is proposed. These methods are so simple that three-dimensional perspective images with shading can be produced rapidly. This paper also describes an architecture based on these methods for generating animation interactively.