Essential Series Springer-Verlag London Ltd. Also in this series: John Cowell John Hunt Essential Visual Basic 4.0 fast Essential JavaBeans fast 3-540-19998-5 1-85233-032-5 John Cowell John Vince Essential Delphi 2.0 fast Essential Virtual Reality fast 3-540-76026-1 1-85233-012-0 John Cowell John Cowell Essential Java fast Essential Visual J++ 6.0 fast 3-540-76052-0 1-85233-013-9 John Cowell John Cowell Essential Visual Basic 5.0 fast Essential Java 2 fast 3-540-76148-9 1-85233-071-6 Duncan Reed and Peter Thomas John Cowell Essential HTML fast Essential Visual Basic 6.0 fast 3-540-76199-3 1-85233-071-6 John Cowell Ian Chivers Essential Delphi 3 fast Essential Visual C++6.0 fast 3-540-76150-0 1-85233-170-4 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