Volume 09 (1990)
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Item Calendar of Events(Blackwell Publishing Ltd and the Eurographics Association, 1990)Item EURASIP Short Course Medical Imaging: Techniques and Trends(Blackwell Publishing Ltd and the Eurographics Association, 1990)Item Project DIGIS: Building Interactive Applications by Direct Manipulation(Blackwell Publishing Ltd and the Eurographics Association, 1990) Bos, Jan van den; Laffra, ChrisAbstractDIGIS is a design and implementation system for developers of general purpose interactive applications (IA). It is itself an interactive system that accomplishes its task by Direct Manipulation techniques, in principle without using a programming language. DIGIS is a generator in the form of a window-based workbench. It has two input sources. One is a toolkit of predetined interaction tools consisting of prototypes and instances. The other is the set of predetined application procedures thai make up the application part of the IA. The application procedures do not handle user input but may handle textual or graphical screen output. The task of the developer is to build the user interface by selecting the appropriate interaction tools. tailor them to the interface, and tie them to application procedures. This includes the visual representations of interaction tools, their prompts, echoes and feedback. In the process he maps user input to parameter lists for the application procedures, and return parameters to interface output. DIGIS will also support the detinition of composite input (interaction patterns such as sequences). Unix and X are the initiat operating environment, adaption of the input sources to PCTE. OSF/Motif, and Open Look is feasible and anticipated.The design of DIGIS is based on a hierarchical interaction model that is the second focus of this paper. The implementation will be done using PROCOL, a locally developed concurrent object-oriented language. which offers protocols that support composite input. The language is a superset of C, and therefore fully compatible with existing C libraries.ACM Categories and Subject Descriptors: D.2.2 [Software Engineering]: Tools and Techniques -user interfaces, programmer workbench-D.3.3 [Programming Language]: Language Constructs -input/output, programming structures-H.1.2 [Models and Principles]: User/Machine Systems -human factors-1.3.6 [Computer Graphics]: Methodology and Techniques - interaction techniques, ergonomics, languages:Item Shading and Shadowing with Linear Light Sources(Eurographics Association, 1990) Poulin, Pierre; Amanatides, JohnIn virtually all rendering systems, linear light sources are modeled with a series of point light sources that require considerable computing resources to produce realistic looking results. A general solution for shading surfaces illuminated by a linear light source is proposed. A formulation allowing for faster computation of the diffuse component of light reflection is derived. By assuming Phong's specular component, simple, inexpensive and convincing results are produced with the use of a Chebyshev approximation. A shadowing algorithm is also presented. As shadowing from linear light sources is expensive, two acceleration schemes, extended from ray tracing, are evaluated.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 HYPERIMAGES - AN ALTERNATIVE TO THE CONVENTIONAL DIGITAL IMAGES(Eurographics Association, 1990) Bieri, HanspeterHyperimages represent a variation of the conventional digital images which implies pixels of different dimensions within the same image. The extent of a hyperimage is the disjoint union of all pixel extents it contains, which are relatively open unit cubes with respect to the euclidean topology of the underlying space. This approach is independent of any specific dimension of image and space, respectively, and allows strict partitioning of images into subimages, not just subdividing. The applicability of hyperimages is illustrated by a number of algorithms useful in image analysis.Item General Assembly of the EUROGRAPHICS Association(Blackwell Publishing Ltd and the Eurographics Association, 1990)Item Eurographics 90 Tutorials Montreux - Switzerland - September 3-4, 1990(Blackwell Publishing Ltd and the Eurographics Association, 1990) Herman, IvanItem Computer Graphics and Computer-Aided Design Literature: A Keyword-Indexed Bibliography for the Year 1989(Blackwell Publishing Ltd and the Eurographics Association, 1990) Owen, JonItem Mathematical Models for Semi-globalized Spectral Synthesis(Eurographics Association, 1990) Anjyo, Ken-ichiSemi-globalized spectral synthesis is proposed as a new tool for three-dimensional scene description consisting of many natural objects, such as terrain, sea waves, and clouds. The method is based on the mathematical theory of spectral representation of stochastic processes. In this paper, mathematical models in the method are presented under rigorous formulation and then their stochastic properties are shown. Some simple techniques for practical improvements of the original models in depicting scenes are also explained along with the examples obtained.Item Language for Description of Geometric Configurations(Blackwell Publishing Ltd and the Eurographics Association, 1990) Barbic, Janez; Spegel, MarjanThis contribution is an informal presentation of some concepts, facts, and definitions about general configurations, as well as a description of our proposed GL/0 language for symbolic description of geometric configurations. Emphasis is placed on the demand of invariance of geometric descriptions in the spirit of the Erlangen program of Felix Klein, and on the need for separation between the notions of configuration and of segments. Some possibilities for use of the same ideas in other, not necessarily geometric domains are described.Item SIGGRAPH/EUROGRAPHICS Curriculum Review Call for Reviewers(Blackwell Publishing Ltd and the 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.Item Call for Participation: Computer Graphics and Education 91(Blackwell Publishing Ltd and the Eurographics Association, 1990)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 END USER PROGRAMMING ENVIRONMENTS : INTERACTIVE PROGRAMMING-ON-EXAMPLE IN CAD PARAMETRIC DESIGN(Eurographics Association, 1990) Girard, P.; Pierra, G.; Guittet, L.In recent years, the number of computer end-users who do not know programming has increased rapidly. This new phenomenon has spurred a great deal of research about program design using very different approaches from the usual methods, which, as is well known, are very difficult to learn [1]. This research has touched on many programming fields : physical system simulation [2], graphical interface tailoring [3] and "macros" implementation [4] [5], data base access [6], lessons programming in Computer Aided Teaching [1] ... B.A. Myers [7] suggests a useful taxonomy for classifying these different systems. The three orthogonal criteria he uses define eight categories. A system is much more suitable for end-user programming when it is : - interactive, i.e. able to quickly echo the effect of one step of program designing, - graphic, or visual, i.e. allowing program design by commands working (at least) on a bi-dimensional environment, - associated with a running example, i.e. program designing uses values representing a running example of the program. The goal of this paper is twofold. On the one hand, it looks at a domain, rarely quoted in synthetic reviews [6] [7] [4], where these techniques are often used efficiently, and where end-user programming goes beyond the experimental phase : we are referring to parametric-design in Computer Aided Design (CAD). On the other hand, it presents a graphical interactive programming-on-examples system, named LIKE, which removes most of the problems pointed out by recent studies [7] [5].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 TRIMO A Workstation-Based Interactive System for the Generation, Manipulation, and Display of Surfaces over Arbitrary Topological Meshes(Eurographics Association, 1990) Slusallek, Philipp B.; Seidel, Hans-PeterTRIMO has been designed as a workstation-based interactive system for the generation, manipulation, and display of surfaces over arbitrary toplogical meshes. In addition to rational tensor product Bezier and B-spline surfaces, TRIMO also supports piecewise rational triangular Bezier and B-patch surfaces. TRIMO has been implemented in C++ under the X Window System. Special emphasis has been given to a hierarchical data structure and to a menu-and-mouse-driven hierarchical user interface.Item KA?MOE: A Clausal Language for CAD MOdeling Systems with Morphological Constraints(Blackwell Publishing Ltd and the Eurographics Association, 1990) Milanese, VitalianoA declarative language (KA?MOE) for CAD-CAM modeling is presented. The language is designed to protect topological models constraints and guarantee their inheritance in complex entities built up from simpler ones. By itself, KA?MOE behaves as an evolution of Prolog, which is integrated with primitives for modularization and for privatizing modeling structures so as to guarantee interfacing the language with relational or deductive Data Bases.Item Hemi-Cube Ray-Tracing: A Method for Generating Soft Shadows(Eurographics Association, 1990) Meyer, UrsThis paper presents a new ray-tracing technique for generating soft shadows. The technique treats scenes consisting of light sources and opaque objects which are polygons or polyhedra of arbitrary shape and size. To determine the intensity at a point on a surface, the hemisphere is sampled extensively through the use of hemi-cubes. So-called item-buffer boxes, a combination of itembuffers and buffer boxes, are used to calculate ray intersections as well as to suppress image aliasing. Several methods for reducing aliasing caused by hemi-cubes are discussed. The uniform treatment of rays allows for a straightforward extension of the algorithm to produce fuzzy reflections. The success of the new technique depends on a fast implementation of a visible surface algorithm as provided by today’s high-end graphics workstations. The results are images of realistically illuminated synthetic environments.