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Item 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, DanielThis 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.Item Template-Based Volume Viewing(Blackwell Science Ltd and the Eurographics Association, 1992) Yagel, Roni; Kaufman, ArieWe 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.Item Modelling and Programming Evolutions of Surfaces(Blackwell Science Ltd and the Eurographics Association, 1992) Chen, X.; Lienhardt, P.In recent years, a lot of work has been done on modelling natural phenomena and simulating the evolution of natural objects. For instance, procedural methods have been developed for simulating corpuscular phenomena and tree growth. In this paper we present a new procedural method for simulating evolutions of subdivisions of surfaces (i.e. partitions of surfaces into vertices, edges and faces). The representations of topology, embedding and photometry are clearly distinguished in the geometric model used for the representation of such subdivisions and thus, each of these features may be evolved independently (as in natural metamorphoses). Evolutions are achieved by applying topological and embedding operations on the geometric model. Control of these evolutions is based upon the behaviour concept. Behaviours (i.e. sets of operations) are associated with cells of the modelled subdivision. At each step, and for each cell, the corresponding behaviour is applied to the cell. The definition and computation of parameters have been studied, in order to control such evolutions. The method has been implemented and tested with many examples of surface evolutions (mainly evolutions of vegetal surfaces: leaves, flowers). Based on the method, a language has been defined for programming surface evolutions.Item Stochastic Motion-Motion Under the Influence of Wind(Blackwell Science Ltd and the Eurographics Association, 1992) Shinya, Mikio; Fournier, AlainStochastic approaches are very effective for modelling natural phenomena. This paper presents a motion model based on a stochastic process as well as physics, and proposes motion synthesis techniques for stochastic motion-motion under the influence of wind.The motion synthesis process is modelled by a cascade system of three components: wind model, dynamic model, and deformation model. Wind models produce spatio-temporal wind velocity fields using the power spectrum and auto-correlation of wind, just like fractal geometry. Dynamic models describe the dynamic response of the systems, using equation systems or response functions. Deformation models produce deformed shapes of objects according to the geometric models of the objects and the results of the dynamic systems.The biggest advantage of the model is its generality and consistency. The model is applicable to most of the existing trees and grass models, including structural models, particle systems, impressionist models, and 3D texture. It is demonstrated that the coupling of stochastic approaches and physically-based approaches can synthesize realistic motion of trees, grass and snow with modest computational cost.Item Two-manifold cell-decomposition of r-sets.(Blackwell Science Ltd and the Eurographics Association, 1992) Falcidieno, Bianca; Ratto, OrnellaThis paper discusses the relationships studied between manifold solids and r-sets by defining an r-set as a decomposition in two-manifold cells. This decomposition is represented as a graph (Two-manifold Cell Decomposition graph TCD) in which each node corresponds to a 2 manifold component of the regular set, while each arc or hyperarc defines a non-manifold adjacency between components. The TCD model and data structure encoding it were designed in order to be compatible with a traditional boundary architecture.Item An Efficient Massively Parallel Rasterization Scheme For a High Performance Graphics System(The Eurographics Association, 1992) Karpf, S.; Chaillou, C.; P F ListerWe present in this paper the IMOGENE II system, a massively parallelMulti-SIMD graphics system. This architecture uses a new rasterization scheme combining Object Parallelism and Parallel Virtual Buffers. This scheme leads to a better efficiency than other massively parallel SHvlD systems, and allows a cost-effective, powerful and easily expandable system to be designed. The system consists of several SIMD ScanConversionPipelines each connected to a Multi-Level Virtual Buffer, a Shading Unitcomputing true Phong Shading, a Virtual Accumulation Frame Buffer for anti-aliasing,and a. classical Frame Buffer.Item The Fractal Nature of an Ecological Model(Blackwell Science Ltd and the Eurographics Association, 1992) Bennan, Wang; Yin, ShiWith the help of computer graphics, the chaotic behaviour of an ecological model in the complex plane has been investigated. Convergence maps that show multi-fractal characteristics (science) and beautiful patterns (art) are presented.Item An Object-Oriented View of the User Interface(Blackwell Science Ltd and the Eurographics Association, 1992) Zhou, Tom Z.-Y.; Kubitz, William J.The object-oriented view of the user interface presented here is a model of object responsibilities-sharing and cooperation for a typical user interface. The model regards the user interface as a three-layer architecture, with the application contributing to one of the layers called the application exposure, The model seeks to promote user interface software reuse by coupling the user interface and the application with well-defined message protocols, by properly allocating user interfacefunctions to the layers so as to reduce and discipline their dependencies, and byfactoring complex abstractions into reusable secondary components.Item An Open Model for Hypermedia and Its Application to Geographical Information Systems(Blackwell Science Ltd and the Eurographics Association, 1992) Hall, W.; Simmons, D.This paper describes the design and implementation of a multimedia information management environment that is based on an open model for hypermedia. The model, known as Microcosm, is currently implemented in Microsoft Windows and supports many different media types. The open nature of the model and the separation of the links from the data, allows links to be applied across any application running under Windows or the OS/2 version 2 desktop, thus creating a truly integrated environment. One example, which is, discussed in the paper, is the integration of a hypermedia database with a geographical information system. The paper also discusses the application of novel interfaces to dynamic media within a hypermedia system, including the use of moving icons (micons).Item Area Sampling Buffer: Tracing Rays with Z-Buffer Hardware(Blackwell Science Ltd and the Eurographics Association, 1992) Sung, KelvinAn algorithm that allows the use of z-buffer hardware in assisting area sampling for a ray tracing style renderer is described. The implementation issues involved in discretizing the sampling area and light source area are discussed and solutions are proposed. The effects of the hardware-assisted ray tracing approach on frame-buffer systems and image synthesis processes are considered.