Volume 09 (1990)
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Item 3D Display: Synthetic Image Generation and Visual Effect Simulation(Blackwell Publishing Ltd and the Eurographics Association, 1990) Theoharis, T. A.; Travis, A. R. L.; Wiseman, N. E.Two viewing models are presented for a promising type of three dimensional display: they are based on parallel oblique and perspective oblique projections respectively. A detailed simulation compares the quality of the images that will be produced by each projection type and points out potential problems. The time necessary to alter the image of the three dimensional display will be comparable to that of conventional displays by the use of a simple parallel processing scheme.Item 3D MODELLING AND MOTION OF DEFORMABLE SOLIDS FROM 2D IMAGES(Eurographics Association, 1990) Neveu, Marc; Faudot, DominiqueOur work purpose is to elaborate a geometric and motional model for deformable solids, known only by a very small number of general crosssections images. We start from a generic 3D model of the studied solid we distort according to detected boundaries in the above mentioned images. To give the solid motion model, our work uses moving point constraints and inbetweening methods on an image sequence : we select keyframes on which we interpolate characteristic points. Then we use Coons patches to compute the inbetween frames and realize an animation? On an echocardiographic application, we obtained good results in the model precision and detected edges by image processing similar to cardiologists' hand drawn edges. Besides, the model distortion, characteristic points tracking and 2D motion simulation are encouraging, although improvements are necessary.Item ADAPTIVE POLYGONIZATION OF IMPLICIT SURFACES USING SIMPLICIAL DECOMPOSITION AND BOUNDARY CONSTRAINTS(Eurographics Association, 1990) Velho, LuizThis paper presents a method to generate a polygonal approximation of implicit surfaces. Space partitioning by simplicial decomposition is used to sample the surface, which provides an unambiguous framework for polygon creation. Simplices are adaptively subdivided in order to faithfully represent the surface with a minimum number of elements. The space subdivision is done recursively, without the need of additional data structures to keep track of the process, which usually results in large memory requirements. Furthermore, boundary constraints are imposed on the surface tesselation to overcome the problem of discontinuities usually associated with adaptive methods.Item An Approach to Hierarchical Input Devices(Blackwell Publishing Ltd and the Eurographics Association, 1990) Duce, D. A.; Liere, R van; Hagen, P.J.W. tenThis paper shows how a formal description of the GKS input model can be extended to include hierarchically structured input devicesItem AN APPROACH TO IMPROVE THE RELIABILITY OF BOOLEAN OPERATION ON A PAIR OF POLYHEDRA(Eurographics Association, 1990) Li, Xinyou; Sun, Jiaguang; Tang, ZeshengIt is essential and pressing to improve reliability of Boolean operations in geometric modelling systems. The Boolean operations in commercial systems now available are not reliable enough because of numerical calculation errors. Numerical calculation errors hinder us from determining set membership classifications exactly. Some classifications are ambiguous because they are dependent on adopted computing tolerance. Thereby interrelated classifications may conflict with each other and it is very difficult to get correct results of Boolean operations In many cases. We introduce a reliable Boolean operation algorithm which solves the conflicts among interrelated classifications before implementation of Boolean operation by use of reasoning technique. The algorithm has replaced the modelling module of the geometric modelling system GENS 2.0 to form a new system GENS 2.1 on Apollo and Sun workstations. According to tests and compared with Geomod 3.9 and I/ENS, GENS 2.1 is much more reliable.Item AN APPROACH TO THE FORMAL SPECIFICATION OF THE COMPONENTS OF AN INTERACTION(Eurographics Association, 1990) Faconti, Giorgio P.; Paterno, FabioIn this paper we present the preliminary results from a work aiming to the formal specification af a model suitable for the description of interactive graphics program within the framework defined by the Reference Model for Computer Graphics Systems, actually under development within the International Organization for Standardization. The architecture defined by the Computer Graphics Reference Model, at its actual state of development, is shortly presented with particular attention paid to the concepts used in the paper. Following, the components of a basic interaction are identified and described as a set of independent communicating processes, referred to as an interactor. The relationships between interactors are described in terms of the communication between their component processes by using ECSP-like constructs.Item The Architecture of a Prototype System for Drawing Data Structures(Eurographics Association, 1990) Ding, Chen; Mateti, PrabhakerAutomatic drawing of aesthetically pleasing data structure diagrams is a challenging problem which has attracted much research attention. In building such a system, we are confronted with four basic problems: (1) proper user involvement, (2) good user customization facilities, (3) aesthetics, and (4) efficiency. Each of the above problems has been attacked separately in the past. In this paper, we describe a prototype which brings the above four issues together and builds a powerful, usable, and natural automatic diagram drawing system.Item AUTOMATIC MODELLING OF NATURAL SCENES FOR GENERATING SYNTHETIC MOVIES(Eurographics Association, 1990) Koch, ReinhardA model based analysis by synthesis algorithm is presented. It combines image analysis and synthesis techniques to obtain a three dimensional scene description and to generate synthetic movies out of that scene description. A 3D model world is generated automatically out of TV image sequences containing 3D objects with naturally textured surfaces. The objects are projected into the 2D image domain and compared with subsequent images of the sequence to be analyzed. Differences between input and synthesized images serve to extract shape, motion and surface texture parameters and to adapt the 3D model scene. The model data base can be manipulated to generate synthetic movies with highly realistic, natural looking images.Item Book Reviews(Blackwell Publishing Ltd and the Eurographics Association, 1990)Book reviewed in this article:Reviewer: Ralph Martin. University of Wales College of CardiffItem Book Reviews(Blackwell Publishing Ltd and the Eurographics Association, 1990)Book reviewed in this article:Advances in Computer Graphics V Purgathofer, W., and Schiinhut, J. (editors)An Introduction to Ray Tracing, Glassner, AS. (editor)Item A Browser for Large Directed Graphs(Blackwell Publishing Ltd and the Eurographics Association, 1990) Bovey, J. D.The paper describes an experimental graph browsing tool which provides fast interactive browsing on very large graphs. The particular graph for which the program was developed is based on the distributed tile system of a group of workstations but there is no reason why the same techniques should not be used on graphs from other sources.Item Calendar of Events(Blackwell Publishing Ltd and the Eurographics Association, 1990)Item Calendar of Events(Blackwell Publishing Ltd and the Eurographics Association, 1990)Item Calendar of Events(Blackwell Publishing Ltd and the Eurographics Association, 1990)Item Call for Participation: Computer Graphics and Education 91(Blackwell Publishing Ltd and the Eurographics Association, 1990)Item CHARACTERIZATION OF TOPOGRAPHIC SURFACES(Eurographics Association, 1990) Falcidieno, Bianca; Spagnuolo, MichelaThis paper presents a method for extracting and representang features of a topographic surface approximated by triangular tales An algorithm as given which computes characteristic regions (a. e. regions having concave, convex or planar shape), characteristic lanes (ridges, ravines, generic creases) and characteristic points (maxima, minima, saddle points) The result as a new surface description an terms of an attributed hypergraph representation called Characteristic Region Configuration Graph, an which characteristic regions are considered the basic describers of the surface shape and correspond to the nodes of the graph, whale the arcs and hyperarcs represent the relationships between regions derived from characteristic lanes and pointsItem COLOR IMAGE RECONSTRUCTION FROM NONUNIFORM SPARSE SAMPLES USING A THIN PLATE MODEL(Eurographics Association, 1990) Metaxas, Dimitris; Milios, EvangelosIn this paper we solve the problem of reconstructing a color image from sparse, noisy, and nonuniformly distributed color measurements. We apply a method for reconstructing a surface from sparse depth measurements to each of the R, G and B components of the color data, by treating each as a surface, with depth measurements being the R, G and B values. We apply this method to the reconstruction of nonuniformly distributed sparse color data from even 12.5% of the pixels, if no discontinuities are given and from 6.25% of the pixels, if the discontinuities are given. Also we present results of reconstructing a corrupted version of the original image with Gaussian noise of zero-mean and standard deviation 30 from 25% of the data, for color levels between 0 and 255. The applicability of the method is independent of the choice of the color space used.Item COLOR SHADING IN 2D SYNTHESIS(Eurographics Association, 1990) Bourdin, J.J.; Braquelaire, J.P.In interactive 2D synthesis applications, features for filling regions are generally elementary (uniform colouring, filling with a regular pattern.. .). Interactive design of 2D colour shadings raises two major problems: the difficulty of specifying a shading precisely, and the rapidity of related filling algorithms. In this paper, we propose a model to specify 2D colour shading of a region by decomposing it into two components: a support describing the “shape” of the shading, and a colouring function defined on this shape. We then present an incremental algorithm for support generation.Item Colour Illustrations(Eurographics Association, 1990) -Item Combining Graphics and Windowing Standards in the XGKS System(Blackwell Publishing Ltd and the Eurographics Association, 1990) Rogers, Greg; Sung, Kelvin; Kubitz, WilliamIn the past few years we have seen the acceptance of standards for both two and three dimensional computer graphics. Also during this time, the workstation community has converged on a common windowing system. This paper discusses the problems encountered in implementing graphics standards such as GKS and PHIGS PLUS within the X Window System environment.