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Now showing 1 - 10 of 1179
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    Simulation of Facial Muscle Actions Based on Rational Free Form Deformations
    (Blackwell Science Ltd and the Eurographics Association, 1992) Kalra, Prem; Mangili, Angelo; Thalmann, Nadia Magnenat; Thalmann, Daniel
    This paper describes interactive facilities for simulating abstract muscle actions using Rational Free Form Deformations (RFFD). The particular muscle action is simulated as the displacement of the control points of the control-unit for an RFFD defined on a region of interest. One or several simulated muscle actions constitute a Minimum Perceptible Action (MPA), which is defined as the atomic action unit, similar to Action Unit (AU) of the Facial Action Coding System (FACS), to build an expression.
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    The Impulse Graph: A New Dynamic Structure For Global Collisions
    (Blackwell Publishers Ltd and the Eurographics Association, 2000) Baciu, George; Keung Wong, Sai
    In interactive virtual environments and dynamic simulations, collisions between complex objects and articulated bodies may occur simultaneously at multiple points or regions of interference. Many solutions to the collision response problem are formulated based on the local pair-wise contact dynamics. In this article, we present a new solution to the global interactions and dynamic response between multiple structures in a three-dimensional environment. This is based on a new dynamic impulse graph that tracks the reaction forces through the entire system and gives a global view of all the interactions in a multibody system.
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    Modelling and Rendering Graphics Scenes Composed of Multiple Volumetric Datasets
    (Blackwell Publishers Ltd and the Eurographics Association, 1999) Leu, Adrian; Chen, Min
    This paper presents a method for modelling graphics scenes consisting of multiple volumetric objects. A two-level hierarchical representation is employed, which enables the reduction of the overall storage consumption as well as rendering time. With this approach, different objects can be derived from the same volumetric dataset, and 2D images can be trivially integrated into a scene. The paper also describes an efficient algorithm for rendering such scenes on ordinary workstations, and addresses issues concerning memory requirements and disk swapping.
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    Filtered Jitter
    (Blackwell Publishers Ltd and the Eurographics Association, 2000) Klassen, R. Victor
    Jitter is one popular way of generating samples for stochastic sampling in computer graphics. The Poisson disk distribution better approximates that of the human photomosaic. In this paper we examine the spatial and frequency space behaviour of a number of existing algorithms for generating stochastic samples and propose a new algorithm based on low pass filtering a jittered set of displacements. The distribution is at least as much like that of the human photomosaic as any existing algorithm, while being fast to compute.
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    A Graph-Based Approach to Surface Reconstruction
    (Blackwell Science Ltd and the Eurographics Association, 1995) Mencl, Robert
    A new approach to the reconstruction of a surface from an unorganized set of points in space is presented. The point set may for example be obtained with a laser scanner or a manual digitizing tool, and is the only source of information about the shape of the acquired object. The basic idea is to calculate the Euclidean minimum spanning tree (EMST) of the given points. The EMST is then augmented to the so-called surface description graph (SDG). Finally the wire frame defined by the SDG are filled with triangles. The advantage of our approach is that also highly non-convex and even disconnected surfaces are reconstructed quite reliably. This is demonstrated for a variety of data sets.
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    Template-Based Volume Viewing
    (Blackwell Science Ltd and the Eurographics Association, 1992) Yagel, Roni; Kaufman, Arie
    We present an efficient three-phase algorithm for volume viewing that is based on exploiting coherency between rays in parallel projection. The algorithm starts by building a ray-template and determining a special plane for projection - the base-plane. Parallel rays are cast into the volume from within the projected region of the volume on the base-plane, by repeating the sequence of steps specified in the ray-template. We carefully choose the type of line to be employed and the way the template is being placed on the base-plane in order to assure uniform sampling of the volume by the discrete rays. We conclude by describing an optimized software implementation of our algorithm and reporting its performance.
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    Constructive Page Description Opening Up the Prepress World
    (Eurographics Association, 1991) Samara, Veronika; Wiedling, Hans-Peter
    Constructive Page Description (CPD) is an overall approach allowing different kinds of data to be exchanged between a variety of systems and manipulated in arbitrary system environments. Fully changeable pages, which keep information for modification as long as necessary, as well as fully assembled pages, ready for the printing process, can be constructed by the use of CPD. Moreover, descriptions of data as well as operations can be distributed, and so allow the use of networking facilities. CPD is thereby very flexible in handling, combining, and exchanging data and operations used in the construction of pages. In sum, CPD helps bridge the gap between the printing and the computer graphics world; it is an approach to lead prepress towards an open system architecture.
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    Faster Phong Shading via Angular Interpolation
    (Blackwell Publishing Ltd and the Eurographics Association, 1989) Kuijk, AAM.; Blake, E.H.
    One of the most successful algorithms that brought realism to the world of 3D image generation is Phong shading. It is an algorithm for smooth shading meshes of planar polygons used to represent curved surfaces. The level of realism and depth perception that can be obtained by Phong shading is attractive for 3D CAD applications and related areas. However, per pixel computation costs which were too high and/or artifacts, introduced by some of the more efficient evaluation methods and apparent only when displaying moving objects, are major factors mat blocked the common usage of Phong shading in highly interactive applications.In this paper we present angular interpolation for Phong shading planar polygons. Angular interpolation was a method especially designed to meet requirements as imposed by special purpose hardware we developed1, but turned out to be generally applicable. The angular interpolation method appears to be very efficient and reduces artifacts when displaying moving objects. Ideally a shading algorithm imposes no need for subdivision of patches as presented by the solid modelling system. Shading calculation via angular interpolation yields such an ideal algorithm. We will describe two alternative evaluation methods that trade off evaluation cost against level of accuracy. They both can handle light source and view point at arbitrary distances, but differ in level of accuracy. As a consequence these alternative evaluation methods do impose restrictions on the topology of patches and light sources. However, generally, the limitations imposed by these alternative shading methods are much more liberal than the limitations on patch size imposed by the geometry.The most economic evaluation method we present can incrementally compute the colour intensity along a scanline by two additions per pixel. The methods presented are generally applicable and can easily be implemented in hardware.
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    Algorithm for Clipping Arbitrary Polygons
    (Blackwell Publishing Ltd and the Eurographics Association, 1989) Andreev, Rumen D.
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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.