EG1985 Proceedings (Technical Papers)
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Item A 3-D CELLULAR FRAME BUFFER(The Eurographics Association, 1985) Kaufman, Arie; Bakalash, Reuven; C.E. VandoniA new architecture for storing and processing of threedimensional (3-D) graphics is described, The 3-D objects are discretized and stored in a full 3-D cellular memory of voxels. A 3-D graphics processor scan-converts 3-D geometric objects into the cellular representation. A 3-D frame buffer processor manipulates 3-D cellular sub-boxes and controls 3-D interaction. Displaying 2-D orthographic projections from a given view position and direction is accomplished by a 3-D viewing processor. With this new architecture, there is neither a need for repeatedly scan-converting modified geometric objects nor a need for removing hidden-surfaces.Item BICEPS - THE INTERACTIVE GRAPHICS AIDED SYSTEM FOR BI-DIMENSIONAL GEOMETRY YODELING, NESTING AND FLAME CUTTING TECHNOLOGY(The Eurographics Association, 1985) Kobvlinski, Wiktor J.; C.E. VandoniAn essential condition for effective usage of numerically controlled devices is their correct and efficient programming. Especially in cutting applications every nesting layout requires a new control program tape. The BICEPS system referred here has been implemented in work shops with both: batch production - very stable one and simple part cutting in repair shops where every day new parts are manufactured. In both cases significant material savings (by narrow nesting) and reduction of production preparation time are obtained. The present paper deals with the very first step of production preparation process: modeling of the geometry of Bi-dimensional (2D) contours of Darts manufactured.Item Item A CONCEPT FOR A GKS MACHINE(The Eurographics Association, 1985) Herman, Iván; Reviczky, János; Tolnay-Knefély, Tibor; C.E. VandoniGeneral ideas for the creation of a very intelligent graphic terminal are presented; this terminal should know all GKS functionalities, including the future 3D Standard as well. Multiple Workstation concept is maintained and it i s realized by linking it to a multiple context-frame handling.Item Configuring Reference Systems for Certifying GKS Implementations(The Eurographics Association, 1985) Gbel, M.; Hbner, W.; C.E. VandoniThe development of test packages for certifying GKS implementations is based on the falsification approach which provides a useful framework in the area of software validation. Although there are different test strategies, most of them follow the method of comparing test results against valid reference data. Comparison can be done either in an automatic way or by human judgement. References used for certifying graphics systems are pictures or data which represent a picture at a particular interface. This paper will outline reference data used for testing GKS implementations at the device interface. Furthermore the process of configuring a GKS reference implementation and it's usage for certifying candidate GKS implementations will be presented in detail.Item CREATING CSG MODELLED PICTURES FOR RAY-CASTING DISPLAY(The Eurographics Association, 1985) CORDONNIER, E.; BOUVILLE, C.; DUBOIS, J.L.; MARCHAL, I.; C.E. Vandoni30-picture synthesis systems used for instance in the audiovisual field or networked services require the implementation of easy-to-use aids to composition. This particular composition software realizes the sizing and locating of even complex CSG objects in a simple and direct manner. The Ray-casting method is used for display and designation.Item A CSG LIST PRIORITY HIDDEN SURFACE ALGORITHM(The Eurographics Association, 1985) Jansen, F.W.; C.E. VandoniSeveral algorithms exist for visualizing geometric models defined by constructive solid geometry (CSG). Each of these algorithms is based on standard hidden surface methods, such as ray tracing, scan-line and z-buffer algorithms. In this paper a CSG list priority algorithm is described that is combined with a ray tracing algorithm in the use of a spatial subdivision technique and a CSG list structure to exploit CSG coherence. The combined algorithm is designed for interactive viewing and high quality rendering of CSG models with faceted primitives.Item DETERMINATION OF LOCAL COORDINATE SYSTEMS FOR TEXTURE SYNTHESIS ON 3-D SURFACES(The Eurographics Association, 1985) MA, SONG DE; GAGALOWICZ, ANDRE; C.E. VandoniWe propose and compare three types of local coordinate systems and describe their geometric properties Several results of texture synthesis on 3-D surfaces using these local coordinate systems are presented The synthesis procedure is driven by a texture model including only a small amount of statistical parametersItem EXTENDING GKS TO A DISTRIBUTED ARCHITECTURE(The Eurographics Association, 1985) R.Bettarini,; G.Faconti,; L.Moltedo,; C.E. VandoniThe recently adopted standards in the fields of computer networks and computer graphics has given to the opportunity to start a project to develop a distributed model of the Graphical Kernel System (GKS). The aim of this project is to offer a uniform accessible set of graphical services to the community of scientific and technical users belonging to the National Reserch Council, Universities and other research institutions in Italy. This paper outlines some major problems encountered in the definition of the model of the distributed GKS, and proposes solutions.Item FRACTIONAL BROWNIAN RELIEF : AN EXACT LOCAL METHOD(The Eurographics Association, 1985) FELLOUS, A.; GRANARA, J.; HOURCADE, J. C.; Vandoni, C. E.Fractional Brownian process has been widely used for computer rendering of terrain models. The implementation constraints in Computer Graphics have led to the use of recursive methods, based on some local properties of this model. We present in this article s mathematical study of these local properties and propose a local model for fractal modeling based on strict observance of fractional Brownian probability law.Item A GENERALISATION OF THE TIMMER BLENDING FUNCTIONS FOR BEZIER-TYPE CUBIC CURVES(The Eurographics Association, 1985) NTOKO, NZUMBE-MESAPE; C.E. VandoniAlternative blending functions are derived for a Bezier-type cubic curve touching the middle side of its control polygon. Three shape parameters are used which determine the point on the middle side of the control polygon where the curve touches the polygon. It is then shown that the blending functions proposed are generalizations of those proposed by Timmer.Item GENERALIZATION OF CONTOUR TRACKING IN IMAGE SYNTHESIS, AND APPLICATION(The Eurographics Association, 1985) Hegron, Gerard; C.E. VandoniIn this report, we propose to present most of the treatments about convex and nonconvex colored shapes from a data structure of their contour which is the general approach of contour tracking . Contour filling and oblique cross-hatching take advantage of the coherence between adjacent scan lines and adjacent hatching lines. The position of a point with respect to a nonconvex polygon is solved from filling logic, and the clipping of a line segment by a nonconvex polygon uses the slant cross-hatching idea. We present the clipping of the two nonconvex polygon set. From the area filling of non polygonal blobs, contour tracking is generalized to three geometric problems : position of a point, clipping of a line segment and of a circular arc by a non-polygonal contour, Finally, we discuss the general advantages of contour tracking and application in the writing of a text in a nonconvex polygon.Item GEOMETRIC MODELLING USING EXACT OCTREE REPRESENTATION OF POLYHEDRAL OBJECTS(The Eurographics Association, 1985) Brunet, Pere; Navazo, Isabel; C.E. VandoniIn the last few years, octrees have been proposed for the representation of solids in Geometric Modelling systems. Using them, boolean operations are simple; however, they use a great amount of memory and it is very difficult to obtain smooth graphical outputs from them or to recompute the boundary model. In the present paper, a new class of Octtrees is introduced, which allows face, edge and vertex nodes as well as the classical white, black and grey nodes. The required amount of storage is less than in the case of classical Octtrees, and boolean operations are also simple. Futhermore, there exists an algorithm for the exact recomputation of the boundary model.Item GKS Inquiry Functions within Prolog(The Eurographics Association, 1985) Sykes, Pete; Krishnamurti, Ramesh; C.E. VandoniThis paper discusses the semantics of the GKS inquiry functions within a Prolog environment and illustrates the flexibility built into a proposed Prolog binding.Item GRAPHICAL DATA BASES BUILT ON PEANO SPACE-FILLING CURVES(The Eurographics Association, 1985) LAURINI, Robert; C.E. VandoniThis paper is devoted to the applications of Peano spacefilling curves for modelling graphics information. These curves, based on bit interlacing, allow the modelling, easily, of images with quadtrees, solids with octrees and ray casting techniques, colour coding for paint systems, terrains and some kinds of animation in film bases. Finally, Peano keys and space-filling curves appear to be an efficient tool for logical modelling of computer-graphics objects.Item GRAPHICS PROGRAMMING FOR KNOWLEDGE-GUIDED INTERACTION(The Eurographics Association, 1985) Tibbert, Lee; Bergeron, R. Daniel; C.E. VandoniThis paper describes a design approach that combines knowledge engineering techniques with an interactive graphics program. A prototype for specifying computer systems interactively is used to demonstrate the design approach. The program incorporates a rule-based knowledge engineering module which allows for both data base consistency and the ability to guide the user through an interactive dialogue.Item Graphics Programming with "Archetypes" - A Preliminary Study -(The Eurographics Association, 1985) Martins, Fernando Mar io; Oliveira, Jose Nuno; C.E. VandoniThis paper is a brief report on the initial phase of the formal development of a graphics programming system. At this stage of the specification, the system architecture is just outlined and attention is focussed on the conceptual level. The abstract notion of a graphic 'archetype' is introduced and proposed as a basis for the style of graphics programming to be implemented. The formal description of this meta-concept of the system is sketched.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 An illumination model for ray-tracing(The Eurographics Association, 1985) MONTCEL, Bruno TEZENAS DU; NICOLAS, Alain; C.E. VandoniItem AN IMPROVEMENT OF THE RAY-TRACING ALGORITHM(The Eurographics Association, 1985) COQUILLART, Sabine; C.E. VandoniThis paper describes an improvement of the ray-tracing algorithm. The new method takes advantage of a data structure which allows us to consider only the closest objects to the path of the ray. This technique can be applied to primary and secondary rays. Using this method, the run-time depends more on the complexity of the generated picture than on the complexity of the scene.