Computer Animation ’91

250 Pages·1991·10.427 MB·English

by  Frederic I. Parke (auth.), Prof. Nadia Magnenat Thalmann, Prof. Daniel Thalmann (eds.)

N adia Magnenat Thalmann
Daniel Thalmann (Eds.)
Computer
· ation '91
With 164 Figures, Including 79 in Color
Springer Japan KK
Prof. NADIA MAGNENAT THALMANN
MIRALab, Centre Universitaire d'Informatique
University of Geneva
12, rue du Lac
CH-1207 Geneva
Switzerland
Prof. DANIEL THALMANN
Computer Graphics Lab.
Swiss Federal Institute of Technology
CH-lOIS Lausanne
Switzerland
Cover picture:
Design: Arghyro Paouri
Artistic and technical directors: Nadia Magnenat Thalmann and
Daniel Thalmann
Copyright: MIRALab, University of Geneva and Computer Graphics Lab.,
Swiss Federal Institute of Technology 1990
ISBN 978-4-431-66892-3 ISBN 978-4-431-66890-9 (eBook)
DOI 10.1007/978-4-431-66890-9
This work is subject to copyright. All rights are reserved, whether the whole or
part of the material is concerned, specifically the rights of translation, reprint
ing, reuse of illustrations, recitation, broadcasting, reproduction on microfilms
or in other ways, and storage in data banks.
© Springer Japan 1991
Originally published by Springer-Verlag Tokyo in 1991
Softcover reprint of the hardcover 1s t edition 1991
The use of registered names, trademarks, etc. in this publication does not
imply, even in the absence of a specific statement, that such names are exempt
from the relevant protective laws and regulations and therefore free for
general use.
Preface
This book contains invited papers and a selection of research papers
submitted to Computer Animation '91, the third international work
shop on Computer Animation, which was held in Geneva on May 22-24.
This workshop, now an annual event, has been organized by the
Computer Graphics Society, the University of Geneva, and the Swiss
Federal Institute of Technology in Lausanne. During the international
workshop on Computer Animation '91, the fourth Computer-generated
Film Festival of Geneva, was held.
The book presents original research results and applications experience
of the various areas of computer animation. This year most papers are
related to character animation, human animation, facial animation, and
motion contro!.
NAD IA MAGNENAT THALMANN
DANIEL THALMANN
v
Table of Contents
Part I: Facial Animation
Contral Parameterization for Facial Animation
F.I. PARKE ............. ................ ....... ....................................... 3
Linguistic Issues in Facial Animation
C. PELACHAUD, N.!. BADLER, M. STEEDMAN ............................... 15
Facial Animation by Spatial Mapping
E.C. PATTERSON, P.c. LITWINOWICZ, N. GREENE ......................... 31
A Transformation Method for Modeling and Animation
of the Human Face fram Photographs
T. KURlHARA, K. ARAI ............................................................ 45
Techniques for Realistic Facial Modeling and Animation
D. TERZOPOULOS, K. WATERS ................................................... 59
Part ll: Human Modeling and Animation
Generation of Human Motion with Emotion
M. UNUMA, R. TAKEUCHI ..........•............................................. 77
Creating Realistic Three-Dimensional Human Shape Characters
for Computer-Generated Films
A. PAOURl, N. MAGNENATTHALMANN, D. THALMANN ................... 89
Design of Realistic Gaits for the Purpose of Animation
N. VASlLONIKOLIDAKIS, G. J CLAPWORTHY ................................... 101
Planning Human Movement Through Computer Animation
O. FAHLANDER, J. YNGVESSON, I. WALLIN .................................. 115
VII
Part m: Systems and Languages for Motion Synthesis
and Control
Toward an Integrated Motion-Synthesis Environment
S. AMKRAuT, M. GIRARD ......................................................... 131
MacBounce:
A Dynamics-Based Modeler for Character Animation
G. MILLER ........................................................................... 149
Animation Platform:
A Data Management System for Modeling Moving Objects
M.-W. LEE, T.L. KUNII .......................................................... 169
Tools for Artists
M. BRET .............................................................................. 187
Part IV: Rendering Techniques for Animation
Forest: An Interacting Tree Model for Visualizing Forest
Formation Processes by Algorithmic Computer Animation
- A Case Study of a Tropical Rain Forest
T.L. KUNII, H. ENOMOTO ........................................................ 199
Dynamic Scenes Management for Animation
with Ray-Tracing Rendering
H. MAUREL, B. MOISAN, J.P. JESSEL, Y. DUTHEN, R. CAUBET 215
Utilizing Parallel Processing in Computer Animation
F. VAN REETH, E. FLERACKERS ................................................. 227
Extensions of the Color-Cell-Compression-Algorithm
M. PINS ............................................................................... 241
Author Index ....................................................................... 253
Keyword Index ..................................................................... 255
VIII
Part I
Facial Animation
Control Parameterization for Facial Animation
FREDERIC I. PARKE
Abstract
The control mechanisms currently used in facial animation are reviewed. It is argued that
all currently used or anticipated facial animation control schemes should be viewed as
parameterizations. The development of facial animation should be viewed as two
independent activities; the development of "universal" control parameterizations and
interfaces, and the development of optimal techniques to implement facial animation based
on these parameterizations. The development of complete low level parameterizations
enables the development of higher levels of control abstract ion. Several possible directions
for facial animation research are discussed.
Key Words: facial animation, animation control, parameterization
1. Introduction
In recent years there has been considerable renewed interest in computer based facial
animation techniques. The initial efforts to represent and animate faces using computers go
back almost 20 years (Chernoff 1971; Parke 1972; Gillenson 1974). The intent of this paper
is to explore and develop a framework for the control aspects of fa ci al animation. We will
review, consolidate, and hopefully extend the approaches to control of facial animation.
From the animators view point, the important aspects of a facial animation system are the
controllable features and characteristics, the range of control, and how control is
accomplished. From the implementors point of view, the important aspects are the
techniques and algorithms used to actually implement the controllable facial models.
2. Control Parameterization
The unifying theme proposed in this paper is that, from the animators view point,
animation may be viewed as manipulating a set of control parameters. Animation then
becomes the process of specifying and controlling parameter set values as functions of time.
Again from the animators point of view, the interesting quest ions are; (1) what are the
parameters, (2) are the parameters adequate and appropriate, and (3) how are these
parameters manipulated. The animator is not usually interested in the implementation
algorithms or implementation details but only in the animation functionality provided. The
animation system is viewed as a "black box" with (hopefully) a useful, predicatable interface
that produces the desired results. The animator really does not care how the black box
works, only that is does work and does provide appropriate functionality.
4
From the implementors point of view the interesting questions are; (1) what parameters
should be provided, (2) what user interface to the the parameters should be provided, and
(3) what techniques should be used to actually implement the facial animation system.
Most of the work in recent years has concentrated on on the latter of these; on the specific
techniques for implementing facial animation. Relatively little work has been done on
establishing what control functionality and what interfaces should be provided. Questions
concerning useful, optimal, and "complete" control parameterizations remain mostly
unanswered. The functionality provided by each implementation has been primarily
influenced by the characteristics of the particular implementation technique rat her than
attempting to fulfill a weil understood set of functionality and interface goals.
There are two major categories of specification or control parameters. The most often
addressed of these concerns facial expression. The other concerns individual facial shape or
conformation. Conformation control is used to select or specify a particular individual face
from the universe of possible faces. Expression control is concerned with changes of facial
expression. In the ideal case these two categories of control are orthogonal. Conformation
should be independent of expression and expression independent of conformation.
3. Review of Facial Animation Techniques
In most facial animation systems to date, the visible surfaces of the face are modeled as
networks of connected polygons as illustrated in Figure 3. The goal of the various
animation techniques is to control the polygon vertex positions over time such that the
rendered facial surfaces have the desired shapes in each frame of the animated sequence. A
few implementations such as Waite (1989) have used curved surface techniques rather than
polygon modeling techniques. However, the goal of controlling surface shape remains the
same.
3.1 Key Expression Interpolation
Among the earlist and still most widely used schemes for implementing and controlling
facial animation is the use of key expression poses and interpolation. Parke (1972) first
demonstrated the use of this approach to produce viable facial animation. The basic idea
and the control parameterization are very simple - and also limited. The idea is to collect
by some means geometric data describing the face in at least two different expression poses.
Then a single control parameter, the interpolation coefficient in the case of linear
interpolation, is used as a function of time to change the face from one expression into the
other. Figure 1 illustrates this approach. The two key expression poses are shown on the
left and the right of the image. The middle image is an interpolation between the key
poses.
This idea can be expanded in several ways. More than two expression poses may be used.
If for example, four expressions are available then two interpolation parameters may be
used to generate an expression which is a bi-linear blend of the four key poses. If eight key
expressions are available then three interpolation parameters may be used to generate a
tri-linear expression blend. Four interpolation parameters and 16 key expressions allow
blending in a four dimensional interpolation space. Higher dimensionalities are also possible
but probably not useful to the animator since this higher dimension expression
interpolation is not very intuitive.
Another way of exploiting multiple expression poses is to allow pair-wise selection of the
poses and use a single interpolation parameter to blend between the selected poses. This
involves three parameters; starting pose, ending pose, and interpolation value.
5
Figure 1 - Key expression interpolation. The middle face
is an interpolation of the left and right key poses.
Figure 2 - Bi-linear conformation interpolation. The
center face is an interpolated blend of the four corner faces.