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Has files: true × Start date: 1985 × End date: 1989 ×

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Now showing 1 - 10 of 190
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    Free-Form Surfaces Modeling by Evolution Simulation
    (Eurographics Association, 1988) Lienhardt, Pascal
    We 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.
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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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    Blending Rational B-Spline Surfaces
    (Eurographics Association, 1989) Bardis, L.; Patrikalakis, N.M.
    A method for blendin non uniform rational B-spline surface patches, either open or periodic, is developed. he blending surface is expressed in terms of an integral, bicubic B-spline patch. The blend ensures position and normal vector continuity along linkage curves to within a specified accuracy. The linkage curves are either user-defined or are obtained by offsetting the intersection of the two patches using geodesics on each patch. An example illustrates the applicability of our method.
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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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    Architectures for Mass Market 3D Displays
    (Eurographics Association, 1988) Winser, Paul; Bonnet, Thierry; Dumont, Dominique; Mathieu, Yves
    We discuss the specific architecture requirements of real time 3D display systems intended for low cost mass market products of the near future. Vertex transformation and polygon rendering are two processing aspects where hardware acceleration must be used to achieve the performance target. The use of one or more DSP chips as vertex processors is discussed, and two efficient z-buffer implementations described. Antialiasing and texture mapping greatly improve the visual impression at some processing cost.
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    Variations on a Dither Algorithm
    (Eurographics Association, 1989) Pins, Markus; Hild, Hermann
    Mapping continuous-tone pictures into digital halftone pictures, i.e. 0/1-pictures, for printing purposes is a well explored technique. In this paper, one of these algorithms, the two-dimensional error-diffusion algorithm is extended to color pictures and animated pictures. The color picture algorithm is superior to existing algorithms by considering extreme color values as well as adjacent color values. The animation algorithm eliminates the noise created by the correct but varying pixel patterns generated by applying a single picture dithering algorithm on every frame. The power of the algorithms is demonstrated by experiments carried out on synthetic images generated by ray tracing.
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    A Means to Improve the GKS-3D/PHIGS Output Pipeline Implementation
    (Eurographics Association, 1987) Herman, Ivan; Reviczky, Janos
    The output pipeline of GKS-3D/PHIGS isexamined to find some possible points where the implementation could be improved to raise efficiency while remaining strictly within the scope of the Standards. Some interesting results are presented in the paper which have led to a 25-30% improvement in speed when compared to a more conservative implementation.
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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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    An Evaluation of CSG Trees Based on Polyhedral Solids
    (Eurographics Association, 1988) Badouel, Didier; Hegron, Gerard
    Set operation on polyhedra is an important component of Geometric Modeling System (GMS) when a Constructive Solid Geometry (CSG) representation with polyhedral solid primitives is used. Output data will be the unique resulting polyhedron which provides an efficient data structure for displaying objects. With no use of spatial coherency, computational complexity of a set operation is quadratic. The new evaluation scheme called Boolean Octree limits set operation evaluation in a ‘minimal space of calculation’ where primitive boundaries intersect each other and where resulting evaluation participates in the construction of the final resulting object. Boolean Octree computes set operations in a local level providing a linear complexity for geometric calculations. During space subdivision, Boolean Octree has a global view on local CSG tree (projection of the CSG tree in local space) taking into account simplifications of the boolean expression. Set evaluation is done in the local volumes containing only two operands the configurations of which are ‘simple’, that is to say for a local description of an object there is only one vertex with any face number, one edge, or one face.