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Über dieses Buch

This volume contains the research papers presented at the Eleventh Eurographics Workshop on Computer Animation and Simulation which took place in Interlaken, Switzerland, August 21-22, 2000. The workshop is an international forum for research in human animation, physically-based modeling, motion control, animation systems, and other key aspects of animation and simulation. The call for papers required submission of the full papers for review, and each paper was reviewed by at least 3 members of the international program committee and additional reviewers. Based on the reviews, 14 papers were accepted and the authors were invited to submit a final version for the workshop. We wish to especially thank all reviewers for their time and effort in working within the rigid constraints of the tight schedule, thereby making it possible to publish this volume in time for the workshop. We also thank the authors for their contributions to the workshop, without whom this unique forum for animation and simulation work would not exist. We are grateful to the Eurographics Association and especially to Werner Purgathofer from the Technical University of Vienna, for his support in publishing the workshop as a volume of the Springer-Verlag Eurographics Series. We also thank the Eurographics '2000 organisers, especially David Duce, and Heinrich Miiller from the EG board. We are also very grateful to lerrin Celebi for the organization of the review process and and Josiane Bottarelli for the registration process.



Facial Animation and Ageing


A Parametric Tongue Model for Animated Speech

We present a tongue model for use in computer-animated speech. The model is capable of representing tongue shapes during the production of English vowels and consonants as well as general motion of the tongue. Geometrically, the model is composed of a NURBS surface with 60 control points and an 8 + 13 grid of bi-cubic patches. We also present a parameterization of the model that requires only 6 parameters for use during speech production.
Scott A. King, Richard E. Parent

Simulation of Skin Aging and Wrinkles with Cosmetics Insight

This paper briefly reviews the existing approaches employed in computer animation for skin modeling, wrinkle formation and aging process and proposes our approach. Two models have been proposed, one is image-based for rapid prototyping and instant results and another is model based an extension to our earlier work. In the model-based technique skin is considered as a volumetric substance, as opposed to an elastic membrane, having layers of different materials and a finite element method is used for computing the deformation.
The ultimate aim is to devise a practical system, which can enable modeling of skin of an individual person using empirically acquired biomechanical parameters such as Young Modulus. Further, the system is capable to simulate the visual effect of external treatment on the skin, e.g., use of the cosmetics, and exposure to the sun. An application software to this effect has been developed in collaboration with L’Oreal, a renowned cosmetic producer.
Laurence Boissieux, Gergo Kiss, Nadia Magnenat Thalmann, Prem Kalra

A Low Bit-rate Web-enabled Synthetic Head with Speech-driven Facial Animation

In this paper, an approach that animates facial expressions through speech analysis is presented. An individualized 3D head model is first generated by modifying a generic head model, where a set of MPEG-4 Facial Definition Parameters (FDPs) has been pre-defined. To animate realistic facial expressions of the 3D head model, key frames of facial expressions are calculated from motion-captured data. A speech analysis module is employed to obtain mouth shapes that are converted to MPEG-4 Facial Animation Parameters (FAPs) to drive the 3D head model with corresponding facial expressions. The approach has been implemented as a real-time speech-driven facial animation system. When applied to Internet, our talking head system can be a vivid web-site presenter, and only requires 14 Kbps with an additional header image (about 30Kbytes in CIF format, JPEG compressed). The system can synthesize facial animation more than 30 frames/sec on a Pentium III 500 MHz PC. Currently, the data streaming are implemented under Microsoft ASF format, Internet Explorer, and Netscape’s Navigator.
I-Chen Lin, Chien-Feng Huang, Jia-Chi Wu, Ming Ouhyoung

Character Animation


A Grasp-based Motion Planning Algorithm for Character Animation

The design of autonomous characters capable of planning their own motions continues to be a challenge for computer animation. We present a novel kinematic motion planning algorithm for character animation which addresses some of the outstanding problems. The problem domain for our algorithm is as follows: given a constrained environment with designated handholds and footholds, plan a motion through the environment towards a desired goal. Our algorithm is based on a stochastic search procedure which is guided by a combination of geometric constraints, posture heuristics, and distance-to-goal measures. The method provides a single framework for the use of multiple modes of locomotion in planning motions through constrained, unstructured environments. We illustrate our results with demonstrations of a human character using walking, swinging, climbing, and crawling in order to navigate through complex environments.
Maciej Kalisiak, Michiel van de Panne

Motion Tracking with Dynamic Simulation

This paper presents a physics-based real-time animation system for human-like articulated figures. We introduce a novel method for tracking motion data using dynamic simulation. By tracing a desired motion that is kinematically specified by a user using dynamic simulation, our system produces a motion that dynamically and realistically responds to a changing environment ensuring both controllability and physical realism. A tracking controller uses a human strength model as primary constraints, and controls joint angular acceleration within the available range of torque using inverse dynamics. As secondary constraints, the spatial accelerations of the center of mass and end-effectors are controlled. Unlike existing dynamic controllers that control joint torque for each degree-of-freedom (DOF) separately, our dynamic controller controls joint angular acceleration considering the influence of all DOFs using a pseudo-inverse matrix technique. In addition, this paper proposes two extensions of the Newton-Euler inverse dynamics method. One is a proximate solution for handling the closed loop problem. The other is for computing a minimum-moment point between the supporting segment of a figure and the ground for simulating falling motions. We demonstrate the efficacy of our approach by applying our method to a simple lifting task and generating various motions in response to the weight of the lifted load.
Masaki Oshita, Akifumi Makinouchi

ACE: A Platform for the Real Time Simulation of Virtual Human Agents

This paper describes a system platform for virtual human agents simulations that is able to coherently manage the shared virtual environment. Our “agent common environment” (ACE) provides built-in commands for perception and for acting, while the in-between step of reasoning and behavior computation is defined through an external, extendible, and parameterized collection of behavioral plug-ins. Such plug-ins are of two types: the first type defines agent-object interactivity by using a feature modeling approach, and the second type controls the reasoning and behavior of each agent through scripted modules. Our system is analyzed in this paper and a simulation example integrating some modules with a Lisp behavioral system is shown.
Marcelo Kallmann, Jean-Sébastien Monzani, Angela Caicedo, Daniel Thalmann

Hair Modelling


Interactive Hair Styler based on Fluid Flow

In this paper, a new hair styling method is presented. The method draws on remarkable similarities between static hair shape and snapshots of fluid flow around an obstacle. Accordingly, the hair shape is modeled as streamlines of a fluid flow. The model offers an ability to control overall hair shape around the head. At the same time, it gives a possibility of modeling rich details such as waves and curls. Moreover, the continuum property of fluid flow gives a sound basis for modeling complex hair-hair interaction. Based on the model, we develop a fast, intuitive and easy-to-use hair styler. The designer can create intricate hairstyles quickly and easily, without worrying about hair-body and hair-hair interactions. The techniques are also relevant to interactive fluid flow modeling for computer graphics.
Sunil Hadap, Nadia Magnenat-Thalmann

Real-Time Animation of Human Hair Modeled in Strips

A major difficulty in animating human hair results from the large number of individual hair strands in a hairstyle. Current systems of hair modeling and animation use a static, non-scalable representation of hair and consequently, they are better suited for off-line rendering and animation. This paper describes how hair strands can be represented using a more compact and accurate parametric representation. In addition, we propose a novel framework of human hair modeling and animation based on grouping hair strands into strips. Each hair strip is modeled by one patch of parametric surface. Polygon tessellation and the alpha-mapping using hair textures are then applied. Animation is done by keyframing of the control point of surface patches. The parametric representation of hair strips can handle a deformation of any complexity and still appear smooth. We also use multiresolution techniques in the polygon tessellation and apply alpha-mapping to obtain higher speed with different requirements of details for applications. Real-time performance on a PC platform can be achieved with the help of low-end hardware of 3D acceleration.
C. K. Koh, Z. Huang

Deformable Models


Controlling Anisotropy in Mass-Spring Systems

This paper presents a deformable model that offers control of the isotropy or anisotropy of elastic material, independently of the way the object is tiled into volume elements. The new model is as easy to implement and almost as efficient as mass-spring systems, from which it is derived. In addition to controlled anisotropy, it contrasts with those systems in its ability to model constant volume deformations. We illustrate the new model by animating objects tiled with tetrahedral and hexahedral meshes.
David Bourguignon, Marie-Paule Cani

Realistic Deformation of Human Body Shapes

In this paper we propose a new, generic, multi-layered model for automating the deformations of the skin of human characters based on physiological and anatomical considerations. Muscle motion and deformation is automatically derived from an action line that is deformed using a 1D mass-spring system. We cover the muscle layer with a viscoelastic fat layer that concentrates the crucial dynamics effects of the animation. We present results on a female upper torso.
Amaury Aubel, Daniel Thalmann

Implicit-Explicit Schemes for Fast Animation with Particle Systems

Particle systems have been widely employed to animate deformable objects. In order to achieve real time capable systems often simplifications have been made to reduce the computational costs for solving the ODE at the expense of numerical and physical correctness. Implicit-Explicit (IMEX) methods provide a way to solve partly stiff systems efficiently, if the system meets some requirements. These methods allow the solution of the differential equation for particle systems to be computed both correctly and very quickly. Here we use an IMEX method to simulate draping textiles. In particular, our approach does not require any post-correction and works for very stiff materials.
B. Eberhardt, O. Etzmuß, M. Hauth

Modelling and Simulation


An Accurate Model of Wave Refraction Over Shallow Water

A computer model of wave refraction is desirable, in the context of landscape modeling, to generate the familiar wave patterns seen near coastlines. In this article, we present a new method for the calculation of shallow water wave refraction. The method is more accurate than previously existing methods and provides realistic wave refraction effects. We resort to Fermat’s principle of the shortest path and compute the propagation of wavefronts over an arbitrary inhomogeneous medium. The propagation of wavefronts produces a phase map for each terrain. This phase map is then coupled with a geometric model of waves to generate a heightfield representation of the sea surface.
Manuel N. Gamito, F. Kenton Musgrave

Animation and Simulation Techniques for VR-Training Systems in Endoscopic Surgery

We present new animation and simulation techniques to improve the visual realism of virtual reality (VR) based training systems for minimally invasive surgery (MIS). This paper describes the Karlsruhe Training System for Endoscopic Surgery and focuses on the need of animation and simulation methods for realistic visual effects to increase the acceptance of VR-based training systems by surgeons. In detail, interactive modeling and simulation of soft tissue is presented and basic surgical interaction modules are introduced. The remainder of the paper describes a new method for simulating irrigation and suction, new simulation and animation methods for hemodynamics (pulse, bleeding), organ motility, smoke and fluids.
H. K. Çakmak, U. Kühnapfel

Using Cartesian Product for Animation

In the field of geometric modelling for animation, 4D modelling (time being the fourth dimension) seems to be a natural extension of 3D modelling. But time dimension is not easy to apprehend and 4D objects are difficult to interpret and to control in general. We study the application of space-time cartesian product to construct 4D space-time objects; cartesian product is applied to space-time objects for which topological dimension is lesser than 4, and which are easy to interpret as animations. We propose here an interpretation of such objects, and we show how 4D space-time objects, resulting from cartesian product, can be interpreted (and therefore controlled) according to the operands of cartesian product.
X. Skapin, P. Lienhardt


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