EG1985

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    RASTER ROTATION OF BILEVEL BITMAP IMAGES
    (The Eurographics Association, 1985) Hersch, Roger D.; C.E. Vandoni
    A fast raster rotation algorithm based on nearest-neighbour interpolation is described. Essentially, the computation consists of two additions/subtractions and two rounding operations per rotated image pixel. The rotation time, is about equal to the time needed for the pixelwise duplification of an image of the same size. "Nearest-neighbour" interpolation and "ideal" interpolation are compared. Because of non-linearities introduced by binary threshold operations, both interpolation functions are found to be equivalent. From spectral analysis of nearest-neighbour interpolation and from spatial analysis of rotated pixels, it is shown that image frequencies should not be higher than one quarter of the sampling rate. In order to rotate large images, an image memory management module is used for swapping transparently image blocks between main memory and disk.
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    SUBACTOR DATA TYPES AS HIERARCHICAL PROCEDURAL MODELS FOR COMPUTER ANIMATION
    (The Eurographics Association, 1985) Magnenat-Thalmann, N.; D.Thalmann,; C.E. Vandoni
    An innovative kind of procedural model for computer animation is presented in the form of subactor data types. When a subactor data type is defined, many instances of this type may be defined. Each occurrence has the same parameters, but the animation laws applied to the parameters may be completely different. These occurrences of subactors as well as the associated animation laws are controlled in a user-friendly way. Several subactors may be dependent on an actor which may also be globally animated. Subactors based on Coons surfaces and beta-splines surfaces are discussed. Several examples are presented including a clock, a robot and a mask.
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    CREATING CSG MODELLED PICTURES FOR RAY-CASTING DISPLAY
    (The Eurographics Association, 1985) CORDONNIER, E.; BOUVILLE, C.; DUBOIS, J.L.; MARCHAL, I.; C.E. Vandoni
    30-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.
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    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. Vandoni
    An 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.
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    HUTWINDOWS: AN APPROACH TO USER INTERFACE DEVELOPMENT
    (The Eurographics Association, 1985) Koivunen, Marja-Riitta; Mntyl, Martti; C.E. Vandoni
    The 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.
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    A Three-Dimensional Shaded Display Method for Voxel-Based Representation
    (The Eurographics Association, 1985) OHASHI, Toshiaki; UCHIKI, Tetsuya; TOKORO, Mario; C.E. Vandoni
    In 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.
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    DETERMINATION OF LOCAL COORDINATE SYSTEMS FOR TEXTURE SYNTHESIS ON 3-D SURFACES
    (The Eurographics Association, 1985) MA, SONG DE; GAGALOWICZ, ANDRE; C.E. Vandoni
    We 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 parameters
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    GKS Inquiry Functions within Prolog
    (The Eurographics Association, 1985) Sykes, Pete; Krishnamurti, Ramesh; C.E. Vandoni
    This paper discusses the semantics of the GKS inquiry functions within a Prolog environment and illustrates the flexibility built into a proposed Prolog binding.
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    A 3-D CELLULAR FRAME BUFFER
    (The Eurographics Association, 1985) Kaufman, Arie; Bakalash, Reuven; C.E. Vandoni
    A 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.
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    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.
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    MODEL DRIVEN SYNTHESIS OF NATURAL TEXTURES FOR 3-D SCENES
    (The Eurographics Association, 1985) GAGALOWICZ, ANDRE; MA, SONG DE; C.E. Vandoni
    This paper presents a new method for the synthesis of textures on 3-D surfaces. With the exception of fractals, graftals and particle systems used for very restricted types of textures, one basic technique for the faithful reproduction of textures has been presented in the literature up to now. In this standard method, textures are synthesized by mapping a rectangular template onto a patch of the curved surface. In the method proposed here, the synthesis is achieved continuously on the surface by interpolating only statistics of the texture which have a much narrower spectrum than the texture itself so that there are no aliasing effects. A vast class of textures can be reproduced with a visual appearance similar to the reference texture used. The method applies for any 3-D surface and is relatively quick and easy.
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    THE USE OF GRAPHICAL SYMBOLIC COMMANDS (ICONS) IN APPLICATION PROGRAMS
    (The Eurographics Association, 1985) Woodgate, H. Sam; C.E. Vandoni
    This paper describes the use of Graphical Symbols (Icons) as a means of communicating operating commands between application program and users. detailed in the paper is the operational command system for a "Spread Sheet Calculator" which was &signed to be driven entirely by Graphical Symbols using a "point and activate" command method. 83 Graphical Symbols were required to operate the program and these were developed using a "graphical symbol generator". The example User experiences are also discussed.
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    Graphics Programming with "Archetypes" - A Preliminary Study -
    (The Eurographics Association, 1985) Martins, Fernando Mar io; Oliveira, Jose Nuno; C.E. Vandoni
    This 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.
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    AN INTERACTIVE RENDERING TECHNIQUE FOR 3-D SHAPES
    (The Eurographics Association, 1985) KONDO, Kunio; KIMURA, Fumihiko; TAJIMA, Taro; C.E. Vandoni
    This paper describes an interactive rendering technique for giving an impression of 3-D shapes. The following points are discussed : 1) The classification of continuous tone patterns 2) Methods of drawing pictures to enhance 3-D shapes 3) Rules of rendering for the representation of 3-D shapes. The following results are obtained: The use of the rendering rules and CARP facilitates the clear representation of these characteristics and is proved to be effective in creating a picture in which the shapes of bodies are clearly defined,
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    An illumination model for ray-tracing
    (The Eurographics Association, 1985) MONTCEL, Bruno TEZENAS DU; NICOLAS, Alain; C.E. Vandoni
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    PIPEMATIC: A DISTRIBUTED SYSTEM FOR THE DESIGN OF GEOMETRICALLY TIGHT PIPING STRUCTURES
    (The Eurographics Association, 1985) Sulonen, Reijo; Tikkanen, Matti; C.E. Vandoni
    The main principles of an interactive design system intended for the solution of 3D geometric placement problems are described. The first applications for the system will be related to the design of machine rooms in ships where a large number of geometric objects must be placed and connected together with appropriate piping structures. However, the system is application independent. The emphasis of this paper is on the systems structure, algorithmic problems are not dealt with. Implementation of the system is currently underway.
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    A NORMAL-BUFFER VECTORIZED SURFACE SHADING MODEL
    (The Eurographics Association, 1985) Curington, Ian J.; C.E. Vandoni
    A surface rendering implementation is described that separates visibility operations from surface shading operations with a Normal-Buffer data structure. This allows for scene complexity independent shading operations at a fixed computational cost per frame. The Normal-Buffer approach also allows the implementation of a fully vectorized surface-shading algorithm when the shading model is applied to each pixel in the scene. The vectorized shader is described using an array processor with a directly attatched frame store in a high performance scene-generation system.
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    GEOMETRIC MODELLING USING EXACT OCTREE REPRESENTATION OF POLYHEDRAL OBJECTS
    (The Eurographics Association, 1985) Brunet, Pere; Navazo, Isabel; C.E. Vandoni
    In 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.
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    A GENERALISATION OF THE TIMMER BLENDING FUNCTIONS FOR BEZIER-TYPE CUBIC CURVES
    (The Eurographics Association, 1985) NTOKO, NZUMBE-MESAPE; C.E. Vandoni
    Alternative 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.
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    Configuring Reference Systems for Certifying GKS Implementations
    (The Eurographics Association, 1985) Gbel, M.; Hbner, W.; C.E. Vandoni
    The 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.