State-of-the-art in Computer Animation: Proceedings of Computer Animation ’89

223 Pages·1989·12.44 MB·English

by  Daniel Thalmann (auth.)

Cover Picture: From Tin Toy by John Lasseter, Williams Reeves, and Eben Ostby.
© Pixar 1988
N. Magnenat -Thalmann
D. Thalmann (Eds.)
State-of-the-art in
Computer Animation
Proceedings of Computer Animation '89
With 101 Figures
35 of them in Color
Springer -Verlag
Tokyo Berlin Heidelberg New York London Paris
Prof. NADIA MAGNENAT-THALMANN
Centre Universitaire d'Informatique
12, rue du Lac
CH 1207 Geneva
Switzerland
Prof. DANIEL THALMANN
Computer Graphics Lab.
Swiss Federal Institute of Technology
CH 1015 Lausanne
Switzerland
ISBN -13 : 978-4-431-68295-0 e-ISBN- 13 : 978-4-431-68293-6
001: 10.1007/978-4-431-68293-6
Library of Congress Cataloging-in-Publication Data
Computer Animation '89 (1989 : Geneva, Switzerland) State-of-the-art in computer
animation. Includes bibliographies and index. 1. Computer animation - Congresses.
2. Computer graphics - Congresses. I. Magnenat-Thalmann, Nadia, 1946- . II.
Thalmann, Daniel. m. Title. TR897.5.C655 1989760 89-11269 ISBN-13:978-4-431-6-
8295-0
This work is subject to copyright. All rights are reserved, whether the
whole or part of the material is concerned, specifically the rights of trans
lation, reprinting, reuse of illustrations, recitation, broadcasting, reproduc
tion on microfilms or in other ways, and storage in data banks.
© Springer-Verlag Tokyo 1989
Softcover reprint of the hardcover 1st edition 1989
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 gen
eral use.
Preface
This book is the first book which presents a complete scientific
overview of the problematics of Computer Animation. It is divided
into two sections: the first section is devoted to tutorials and sur
veys. The second section describes the state-of-the-art in research
in Computer Animation.
In the first part of this book, the reader gets a general view of
the concepts of Computer Animation: from keyframe to task-level
animation, to specific surveys including A.I., natural language and
simulation for human animation, the use of dynamic simulation,
and facial animation.
In the second part of the book, research papers give a thorough
view of the actual research in Computer Animation. Themes such
as choreography, anthropometry for animated human figures,
motion control, database-oriented animation design, facial expres
sions, motion blur, etc., are described.
These selected topics and papers have been presented during
Computer Animation '89, the first international workshop on Com
puter Animation, which was held in Geneva on June 22-23. This
workshop 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 '89,
the Second Computer-generated Film Festival of Geneva, with
more than 40 selected films, was also held. Many roundtables,
panels, and discussions have also been presented in order to prom
ote interactive links between the researchers, the end-users, and the
artists.
NADIA MAGNENAT-THALMANN
DANIEL THALMANN
Table of Contents
Part I: Tutorials and Surveys
Motion Control: From Keyframe to Task-Level Animation
D. THALMANN .............................. 3
Artificial Intelligence, Natural Language, and Simulation
for Human Animation
N.!. BADLER ............................... 19
An Introduction to the Use of Dynamic Simulation
for the Animation of Human Movement
S. SELBIE .................................. 33
The Problematics of Facial Animation
N. MAGNENAT-THALMANN ...................... 47
Part ll: Research Papers
Simplified Control of Complex Animation
E.F. OSTBY ................................ 59
Message-Based Choreography for Computer Animation
D.E. BREEN, M.J. WOZNY ...................... 69
Anthropometry for Computer Animated Human Figures
M.R. GROSSO, R.D. QUACH, N.l. BADLER .......... 83
Animation Design: A Database-Oriented Animation
Design Method with a Video Image Analysis Capability
M.W. LEE, T.L. KUNII ........................ 97
Animation Control with Dynamics
B. ARNALDI, G. DUMONT, G. HEGRON,
N. MAGNENAT-THALMANN, D. THALMANN 113
Some Methods to Choreograph and Implement Motion
in Computer Animation
N.W. JOHN, P.J. WILLIS ....................... 125
Choreographing Goal-Oriented Motion Using Cost Functions
D.E. BREEN ................................ 141
VIII
Four Dimensional Splines for Motion Control
in Computer Animation
T. SPENCER-SMITH, G. WYVILL .................. 153
Polygon-Based Post-Process Motion Blur
N. MAX ................................... 169
A 3-D Error Diffusion Dither Algorithm for Half-Tone
Animation on Bitmap Screens
H. HILD, M. PINS ............................ 181
A System for Simulating Human Facial Expression
B. GUENTER ............................... 191
The Making of Pencil Test
G. SUSMAN ................................ 203
Shape Distortion in Computer-Assisted Keyframe Animation
E. WESLEY BETHEL, S.P. USELTON ................ 215
Author Index 225
Keywords Index 227
Part I
Tutorials and Surveys
Motion Control:
From Keyframe to Task-Level Animation
DANIEL THALMANN
KEY HORDS: key frame, motion control, kinematics, dynamics, task-level
animation
1. Introduction
1.1 Computer animation and simulation
We know from Computer Graphics courses that 2D and 3D graphical objects may be constructed using
geometric modeling techniques. In a 3D space, scenes are viewed using synthetic or virtual cameras and
they may be lighted by synthetic light sources.
These techniques are important because they allow to visualize any geometrical, physical or chemical
situation to be visualized at any given time. However, the most interesting aspect of many phenomena is
their evolution over time; e.g. motion of electromechanical devices (robots), chemical reactions, fluid
motion, cloud motions, heat conduction. Experiments are often very expensive and sometimes impossible;
e.g. crashes, explosions. It is generally easier and less expensive to produce computer simulation of
phenomena.
Computer graphical simulation is based on animation techniques.
Computer animation consists of modifying a scene over time. Consider for example a 3D scene; we may
say that it is composed of three types of entities: objects, cameras and lights.
Each entity has characteristics which may evolve over time according to arbitrary complex laws:
1) for objects:
-location (car)
-orientation (robot arm)
-size (plant evolution)
-shape (cloud, human heart)
-color (fire, sunrise)
-transparency (fog simulation)
2) for cameras:
-viewer position (flight simulator)
-interest point
-view angle (zoom in).
3) for light sources
-intensity
-location (car light simulation).
1.2 Real-time vs Frame-by-frame
Real-time computer animation is limited by the capabilities of the computer. A real-time image must be
displayed in less then 1/15 second, because the illusion of continuous movement breaks down at slower
speeds. This is a severe limitation, because only relatively simple calculations can be made at this time.
4
Another mode of production is frame-by-frame. Frames are calculated, recorded and then projected at a rate
of 24 (25 or 30) frames/second. The calculation of one frame may take a few seconds or several hours for
very complex images.
We give an example: we move a car 100 meters along the x-axis in 5 seconds; the car is located at <5,0>.
We assume a sequence in 24 frames per second, which gives 120 frames for 5 seconds.
The following program produces such a animated sequence:
in real time:
STEPX:=lQO /120;
create CAR;
place CAR «5,0»;
draw CAR;
for IMAGE:=1 to 120
wait;
erase CAR;
translate CAR «PA SX , 0»;
draw CAR;
frame by frame:
STEPX:=loo / 120;
create CAR;
place CAR «5,0»;
draw CAR;
for IMAGE:=1 to 120
record the frame;
wait;
erase CAR;
translate CAR «PASX ,0»;
draw CAR;
In the near future, very complex animation will be produced in a very shon time, due to the research in
parallel processing and multiprocessors. Image synthesis algorithms like ray-tracing and scan-line may be
easily distributed between several processors. Moreover, animation may be considered as a set of parallel
processes. with and without communications between them.
2. A classification of computer animation methods
Most authors (Hanrahan and Sturman 1985; Parke 1982; Magnenat-Thalmann and Thalmann 1985; Steketee
and Badler 1985; Zeltzer 1985) distinguish between three types of three-dimensional computer animation:
image-based key-frame animation, parametric keyframe animation and algorithmic animation.
2.1 Image-based keyframe animation
Keyframe animation consists of the automatic generation of intermediate frames, called inbetweens, based
on a set of key-frames supplied by the animator. In image-based keyframe animation, the inbetweens are
obtained by interpolating the keyframe images themselves. This is an old technique, introduced by Bunnyk
and Wein (1971). Fig.1 shows the principles to create inbetween frames by linear interpolation between
corresponding venices. When corresponding images have not the same number of venices, it is necessary
to add extra venices, as shown in Fig. 2. A linear interpolation algorithm produces undesirable effects such
as lack of smoothness in motion, discontinuities in the speed of motion and distonions in rotations, as
shown in Fig. 3. Alternate methods have been proposed by Baecker (1969), Bunnyk and Wein (1976),
Reeves (1981). According to Steketee and Badler (1985), there is no totally satisfactory solution to the
deviations between the interpolated image and the object being modeled.