3-D Animation and Morphing using RenderMan A Thesis by: Somhairle Foley B.Sc. Supervisor: Dr. Michael Scott Ph.D. Submitted to the School of Computer Applications Dublin City University for the degree of Master of Science July 1996 Declaration I hereby certify that this material, which I now submit for assessment on the programme of study leading to the award of Master of Science is entirely my own work and has not been taken from the work of others save and to the extent that such work has been cited and acknowledged within the text of my work. Signed: ^ ID Number: Date: Acknowledgments I’d like to thank the School of Computer Applications in DCU for initially funding my research and for letting me complete it when it got delayed The mam person responsible for letting me do this thesis in the first place and for helping me get it finished is my supervisor Dr Michael Scott Thanks Mike Thanks also to the technicians m the Computer Applications school, Jim Doyle and Eamonn McGonigle, and to Tony Hevey m Computer Services This thesis would have been impossible to write without the help of a number of people from Pixar and other places via the Internet There are too many to name individually, but I’d like to thank them all too Finally, I’d like to thank my family and friends, and the postgrads in the lab, past and present, for the more social side of being a postgrad Table of Contents CHAPTER ONE : INTRODUCTION ..................................................................................................1 1 1 T h e sis O u t l in e 1 1 2 A n Introduction t o R e n d e r in g 2 12 1 There are a number of types ofrenderer 3 1 2 2 Photorealism 11 1 3 Introduction t o M o d e l l in g 11 1 3 1 Objects 12 1 3 2 Lights 13 13 3 Camera 15 1 4 R e n d e r in g L ig h t a n d S h a d o w s 15 1 4 1 Gouraud and Phong Shading 16 1 5 A n Introduction t o R e n d e r M a n 17 1 6 R e n d e r M a n a n d t h e R e n d e r M a n In t e r f a c e 18 1 7 G r a p h ic a l T e r m s e x p l a in e d 22 CHAPTER TWO : HISTORY OF ANIMATION............................................. 24 2 1 Introduction 24 2 2 D o c u m e n t e d R e s e a r c h 27 2 2 1 Animation is well researched and documented 27 2 22 Research on morphing tends to be very specific 27 2 2 3 A lot of work on Facial Animation has beenfone 27 2 2 4 Collecting 3-D object data 28 2 3 C o m p u t e r A n im a t io n h a s b e e n implemented in v a r io u s f o r m s 30 2 31 First use of computer animation in feature films 30 2 3 2 European Work 30 2 3 3 The Growth of Special Effects in Movies and Videos 31 2 3 4 Pixar’s new computer generated movie 31 2 3 5 Advertising 32 2 3 6 Desktop Animation 33 2 4 Copyright and Ownership Problems 34 2 5 A w o r d o r t w o a b o u t V isualization 35 2 6 T r a d it io n a l T e c h n iq u e s a r e s t il l r e l e v a n t 3 8 2 7 T h e T w e l v e P r in c ip l e s o f A n im a t io n 39 CHAPTER THREE ANIMATION................................................................................................... 40 3 1 F r a m e -b y -F r a m e 41 3 1 1 Mo d e m Stop-Frame animation 41 3 2 K e y f r a m e s a n d Interpolation 42 3 21 What are keyframes ? 42 3 22 Different methods of interpolating between keyframes 42 3 3 L in e a r v s S p l in e Interpolation 46 3 4 A WORD ABOUT SPLINES 48 3 5 P r o c e d u r a l Interpolation 53 3 6 P a r a m e t r ic C o n t r o l 54 3 7 K in e m a t ic s 55 3 8 T r a c k in g 56 CHAPTER FOUR : MORPHING....................................................................................................... 57 4 1 Introduction 57 4 2 T o p o l o g ic a l a p pr o a c h 59 4 2 1 Original Morphing Methods 59 4 2 2 Advanced Topological Morphing Methods 63 4 3 Im p l ic it Su r f a c e s 65 4 31 Blending Surfaces 68 4 3 2 Morphing soft objects 69 4 3 3 Using skeletal keyframes for animation 70 4 4 Morphing complex objects 72 4 4 1 Grouping Objects using Hierarchies 72 4 42 Cellular Matching 73 4 4 3 Morphing different size composite objects 75 4 4 4 Using Different Primitives 76 4 5 Covering the seams 78 CHAPTER FIVE . IMPLEMENTATION......................................................................................... 81 5 1 O v e r v ie w 81 5 2 U s in g a t w o -p r o n g e d a p p r o a c h 82 5 3 In it ia l r e su l t s w it h pr o c e d u r a l a n im a t io n 83 5 3 1 Structuring RIB objects 87 5 32 Coordinate Systems in RenderMan 88 5 4 M o v in g t h e g o a l p o s t s 89 5 5 S o m h S im p l e - AN interface for viewing and animating objects 91 5 6 Implementing M o r p h in g 94 5 7 P r a c t ic a l Implementation o f M o r ph in g 97 5 8 E x a m p l e s o f m o r p h in g implemented w it h R e n d e r M a n 101 5 9 P hotorealistic R e n d e r M a n a n d t h e B l u e M o o n R e n d in g T o o l s 104 CHAPTER SIX : CONCLUSIONS AND THE FUTURE............................................................... 105 6 1 T o p ic a l C o n c l u sio n s 105 6 2 Implementation C o n c l u sio n s 107 6 2 1 Implementation Difficulties 107 6 3 F u r t h e r a r e a s o f r e s e a r c h 109 63 1 Padding out the blanks 109 6 3 2 Transforming objects into different formats 110 6 3 3 A 3-D World-Wide Web Browser 110 6 3 4 An object oriented animation system 111 6 4 F in a l C o m m e n t s 112 APPENDICES......................................................................................................................................114 Appendix A Bibliography 114 Appendix B 3-D Object File Formats 119 A p p e n d ix C T a b l e o f F ig u r e s 124 A p p e n d ix D P r o g r a m L is tin g s 126 3-D Animation and Morphing using RenderMan Glossary Glossary Composite Object An object which consists of a number of primitives CSG Constructive Solid Geometry A modelling method which allows objects to be combined using set operators DOF Degree of Freedom An independent variable that controls the ability of an articulated object to move relative to another FFD Free Form Deformation A technique used to deform or warp objects independent of the object type K e y fra m e s Frames of an animation that delimit a simple movement or action Using these the frames in-between can be created M o d e llin g The process of describing objects and lights in a 3-D scene M o rp h in g The process of transforming one object into another, usually by changing the surface representation of the object NURBS Non-Uniform Rational B-Splines A powerful type of object which is used to model smooth curved surface objects P atch A smooth curved surface modelling object defined by the combination of two splines Usually bi-cubic or bi-linear P atch m esh A set of connecting patches which can represent a surface P rim itiv e Graphics object which cannot be split into component objects Examples Sphere, Cylinder, Polygon, Patchmesh, NURBS P R M a n (prman) Photorealistic RenderMan Pixar’s highest quality renderer It is the original RenderMan Interface compliant renderer R e n d e rin g The process of creating a computer generated image R e n d e rM a n The public specification issued by Pixar for the description of In te rfa ce 3-D scenes, separating the modelling and rendering phases REYES The underlying algorithm at the heart of PRMan RIB RenderMan Interface Bytestream A file or datastream with 3-D descriptions conforming to the RenderMan Interface S p lin e s Mathematical representations of smooth curves defined by a set of points Can be used for interpolation or approximating surfaces Bézier, Catmull-Rom and NURBS are all types Topology The surface of an object or combination of objects 3-D Animation and Morphing using RenderMan Abstract Abstract an~I~ma~te~\an~e~,mat\vt (1538) la to give life to b to give vigour and zest to 2 to give spirit and support to ENCOURAGE 3 to move to action 4a to make or design in such a way as to create apparently spontaneous lifelike movement preparation of animated cartoons 4b to produce in the form of an animated cartoon meta~mor~pho~sis~\,met~e -'mo r~f<3~s3s\n, pi -pho-ses \,se z\ [L, fr Gk metamorpho sis, fr metamorph noun to transform, fr meta- + morphe form] (1533) la change of physical form, structure, or substance esp by supernatural means b a striking alteration in appearance, character, or circumstances 2 a marked and more or less abrupt developmental change in the form or structure of an animal (as a butterfly or a frog) occurring subsequent to birth or hatching A Websters dictionary definition of the word ‘animate’ strikes to the heart of what animation is about - the illusion of life Giving life to a sequence of pictures is the purpose of animation This has been practised for over a century and nowadays computers are being used to create animations faster and more accurately than ever before Animations are no longer restricted to 'funnies', but can also be models of real-life situations These are based on data not images, and the final images are generated after the data has been processed for unambiguous visualization By representing the data in three dimensions it can be viewed m any number of ways according to the wishes of the 'end' user RenderMan allows a scene to be viewed when defined m three dimensions This can then be viewed as an animated sequence where special effects - such as the metamorphosis of objects (morphing) - may take place to provide a photorealistic animation This thesis will examine how 3-D computer animation in general, and special effects such as morphing m particular, may be implemented using the RenderMan Interface specification and the RenderMan rendering program 3-D Animation