Essential Computer Animation fast : How to Understand the Techniques and Potential of Computer Animation

162 Pages·2000·2.46 MB·English

by  John Vince MTech

Essential Series
Springer-Verlag London Ltd.
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John Vince
Essential
Computer Animation
fast
How to Understand the
Techniques and Potential
of Computer Animation
Springer
John Vince, MTech, PhD, FBCS, CEng
School of Media Arts and Communication, Talbot Campus,
Fern Barrow, Poole BH12 SBB, UK
Series Editor
John Cowell, BSc (Hons), MPhil, PhD
Department of Computer and Information Sciences,
De Montfort University, Kents Hill Campus, Hammerwood Gate,
Kents Hill, Milton Keynes MK7 6HP, UK
ISBN 978-1-85233-141-2
British Library Cataloguing in Publication Data
Vince, John 1941-
Essential computer animation fast : how to understand the
Techniques and potential of computer animation. -
(Essential series)
1. Computer animation 2. Computer graphics
1. Title II. Computer animation fast
006.6'96
ISBN 978-1-85233-141-2
Library of Congress Cataloging-in-Publication Data
Vince, John (John A.)
Essential computer animation fast / John Vince.
p. cm. - (Essential series)
Includes bibliographical references.
ISBN 978-1-85233-141-2 ISBN 978-1-4471-0489-6 (eBook)
DOI 10.1007/978-1-4471-0489-6
1. Computer animation. 1. Title. II. Essential series (Springer-Verlag)
TR897.7 V56 1999
006.6'96-dc21 99-050391
Apart from any fair dealing for the purposes of research or private study, or criticism or review, as
permitted under the Copyright, Designs and Patents Act 1988, this publication may only be
reproduced, stored or transmitted, in any form or by any means, with the prior permission in
writing of the publishers, or in the case of reprographic reproduction in accordance with the
terms of licences issued by the Copyright Licensing Agency. Enquiries concerning reproduction
outside those terms should be sent to the publishers.
© Springer-Verlag London 2000
Originally published by Springer-Verlag London Limited in 2000
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 laws and
regulations and therefore free for general use.
The publisher makes no representation, express or implied, with regard to the accuracy of the
information contained in this book and cannot accept any legal responsibility or liability for any
errors or omissions that may be made.
Typesetting: Camera-ready by author
34/3830-543210 Printed on acid-free paper SPIN 10707824
Dedication
to Megan
Acknowledgments
Writing books is relatively easy. A blank sheet of paper is covered quickly
with words without too much effort, but a hurdle for any author, especially
with a subject like computer animation, is the images. Fortunately, I am lucky
working at the National Center for Computer Animation, as I have access to
some of the most talented students studying computer animation. One such
student is James Hans, who is on a three-year BA in Computer Visualization
and Animation. As James seems to spend every waking moment of his life
modeling and animating, he was an ideal source of images for this book. As
you will discover when you browse through the following chapters, James'
pictures have been used to good effect to illustrate what words fail to express.
Thank you James for your contribution to this book, especially for the cover
and poster design.
I would also like to thank Neil Glasbey, Nigel Sumner, Chris Tucker and
the other postgraduate students who allowed me to use their images.
Viewpoint DataLabs, Inc. provided me with some excellent illustrations in
Chapter 3 of an elephant, a tree and a human heart.
Finally, I would like to thank Digital-X and Next Limit for providing me
with valuable text and images.
Contents
1 WHAT IS COMPUTER ANIMATION? ............................................ 1
Introduction ............................................................................................ 1
What is computer animation? ................................................................. 1
Who should read this book? .................................................................... 3
The aims and objectives of this book ...................................................... 3
Assumptions made in this book .............................................................. 4
How to use the book ............................................................................... 4
2 COMPUTER ANIMATION ................................................................. 5
Introduction ............................................................................................ 5
Animation and computers ....................................................................... 5
The history of animation ......................................................................... 7
Animation and the human visual system ................................................ 9
Persistence of vision ........................................................................... 9
Fusion frequency ................................................................................ 9
Computer animation ............................................................................. 10
Modeling ........................................................................................... 10
Decoration ........................................................................................ 10
Animating............................. ............................................................ 11
Lighting ............................................................................................ 11
Camera control ................................................................................. 12
Rendering ......................................................................................... 12
Compositing ...................................................................................... 13
Conclusion ........................................................................................ 14
3 3D COMPUTER GRAPHICS ............................................................ 15
Introduction .......................................................................................... 15
From computer graphics to computer animation .................................. 15
Principles of computer graphics ............................................................ 16
Cartesian coordinates............................................................................ 16
Modeling simple objects ....................................................................... 17
Interactive modeling ......................................................................... 20
Modeling assemblies ........................................................................ 21
3D libraries ....................................................................................... 22
Internal representation of geometry .................................................. 24
Modeling curves ................................................................................... 25
IX
x Contents
Bezier curves ..................................................................................... 26
NURBS ............................................................................................. 29
Surface patches ...................................................................................... 30
Procedural modeling .............................................................................. 33
Laser scanners ....................................................................................... 33
Perspective view .................................................................................... 34
3D clipping ............................................................................................ 35
Coordinate systems ................................................................................ 37
Transformations .................................................................................... 38
Rendering the image .............................................................................. 38
Color ...................................................................................................... 38
Colored objects ...................................................................................... 39
Light sources ......................................................................................... 40
Illumination models ............................................................................... 41
Ambient light. .................................................................................... 41
Diffuse reflection ............................................................................... 41
Light-source attenuation .................................................................... 42
Atmospheric attenuation .................................................................... 42
Specular reflection ............................................................................. 42
The Phong illumination model .......................................................... 43
The Blinn illumination modeL ......................................................... .43
Shading models ..................................................................................... 44
Constant shading ............................................................................... 44
Interpolated shading .......................................................................... 44
Gouraud shading ................................................................................ 44
Phong shading ................................................................................... 45
Rendering algorithms ............................................................................ 45
Scan-line algorithm ........................................................................... 45
Z-buffer algorithm ............................................................................. 45
Texture mapping ................................................................................... 47
Dynamic textures ............................................................................... 48
Bump mapping ...................................................................................... 50
Environment mapping ........................................................................... 50
Displacement mapping .......................................................................... 50
Shadows ................................................................................................ 52
Transparency ......................................................................................... 52
Radiosity ............................................................................................... 54
Ray tracing ............................................................................................ 54
Volumetric lighting ............................................................................... 57
Shaders .................................................................................................. 57
Advantages ........................................................................................ 59
Disadvantages .................................................................................... 59
The RenderMan Shading Language ...................................................... 59
Aliasing ................................................................................................. 60
Anti-aliasing .......................................................................................... 61
Contents XI
Conclusion ............................................................................................ 61
4 COMPUTER ANIMATION TECHNIQUES .................................... 62
Introduction .......................................................................................... 62
Interpolation ......................................................................................... 63
Function curves ..................................................................................... 65
Parameters ............................................................................................ 67
Channels ............................................................................................... 67
Keyframes ............................................................................................ 67
Inbetweening ........................................................................................ 69
Slow in/Slow out. .............................................................................. 70
Motion paths ......................................................................................... 71
Transformations .................................................................................... 71
Scaling transformation ...................................................................... 71
Translation transformation ................................................................ 72
Rotation transformation .................................................................... 72
Hierarchical animation ......................................................................... 73
Hierarchical geometry .......................................................................... 75
Metamorphosis ..................................................................................... 78
Procedural animation ............................................................................ 79
Forward kinematics .............................................................................. 80
Inverse kinematics ................................................................................ 80
Particle systems .................................................................................... 81
Physical simulation ............................................................................... 84
Collision detection ............................................................................ 85
Rotoscoping .......................................................................................... 87
Constraints ............................................................................................ 87
Free-form deformation ......................................................................... 88
Skeletons ............................................................................................... 88
Conclusion ............................................................................................ 91
5 COMPUTER ANIMATION HARDWARE ...................................... 93
Introduction .......................................................................................... 93
Refresh rate ....................................................................................... 93
Update rate ........................................................................................ 94
Computers ............................................................................................. 95
PC ..................................................................................................... 95
Graphics workstation ........................................................................ 96
Supercomputer .................................................................................. 96
Motion capture ...................................................................................... 96
Mechanical ....................................................................................... 97
Optical .............................................................................................. 97
Electromagnetic ................................................................................ 97
xii Contents
Conclusion ............................................................................................. 98
6 COMPUTER ANIMATION SOFTWA RE ........................................ 99
Introduction ........................................................................................... 99
A generic computer animation system .................................................. 99
Conclusion ........................................................................................... 100
7 POST-PRODUCTION TECHNIQUES ........................................... 101
Introduction ......................................................................................... l 0 1
Digital images ..................................................................................... l 0 1
Spatial resolution ............................................................................. 101
Pixel resolution ................................................................................ 102
Depth channel .................................................................................. 102
Alpha channel .................................................................................. 102
Normalized values ........................................................................... 10 3
Color manipulation .......................................................................... 103
Color balance ................................................................................... 103
Multiplying images .......................................................................... 10 4
Mattes .............................................................................................. 104
Difference matting ........................................................................... 104
Image compositing .............................................................................. 10 5
Chroma-keying ................................................................................ 105
Blemished mattes ............................................................................ 107
Color spill ........................................................................................ 10 7
Tracking .......................................................................................... 10 7
Rendering and compositing ................................................................. 10 7
Interactive and batch processing .......................................................... 10 8
Conclusion ........................................................................................... 10 8
8 COMPUTER ANIMATION APPLICATIONS ••••.••••••••.•.••••••.•••••.•• 109
Introduction ......................................................................................... 10 9
Television graphics .............................................................................. 109
Real-time animation ........................................................................ 110
Computer games .................................................................................. 110
Commercials ....................................................................................... 110
Multimedia .......................................................................................... 111
Legal. ................................................................................................... 111
Computer-aided design ........................................................................ 111
Virtual environments ........................................................................... 112
The Internet ......................................................................................... 113
Simulation ........................................................................................... 113
Digital special effects .......................................................................... 113
Computer-generated films ................................................................... 114