Advanced RenderMan 3: Render Harder SIGGRAPH 2001 Course 48 course organizer: Larry Gritz, Exluna, Inc. Lecturers: Tony Apodaca, Pixar Animation Studios Larry Gritz, Exluna, Inc. Matt Pharr, Exluna, Inc. Christophe Hery, Industrial Light + Magic Kevin Bjorke, Square USA Lawrence Treweek, Sony Pictures Imageworks August 2001 ii iii Desired Background This course is for graphics programmers and technical directors. Thorough knowledge of 3D image synthesis, computer graphics illumination models and previous experience with the RenderMan Shading Language is a must. Students must be facile in C. The course is not for those with weak stomachs for examining code. Suggested Reading Material The RenderMan Companion: A Programmer’s Guide to Realistic Computer Graphics, Steve Upstill, Addison-Wesley, 1990, ISBN 0-201-50868-0. This is the basic textbook for RenderMan, and should have been read and understood by anyone attending this course. Answers to all of the typical, and many of the extremely advanced, questions about RenderMan are found within its pages. Its failings are that it does not cover RIB, only the C interface, and also that it only covers the 10-year- old RenderMan Interface 3.1, with no mention of all the changes to the standard and to the products over the past several years. Nonetheless, it still contains a wealth of information not found anyplace else. Advanced RenderMan: Creating CGI for Motion Pictures, Anthony A. Apodaca and Larry Gritz, Morgan-Kaufmann, 1999, ISBN 1-55860-618-1. A comprehensive, up-to-date, and advanced treatment of all things RenderMan. This book covers everything from basic RIB syntax to the geometric primitives to advanced topics like shader antialiasing and volumetric effects. For any RenderMan professional, this is the book that will be sitting open on your desk most of the time. Buy it. Love it. Tell your friends. “The RenderMan Interface Specification, Version 3.2,” Pixar, 2000. The RI Spec 3.2 is the updated bible of the RenderMan C and RIB API’s and the Render- Man Shading Language. It reflects all of the changes and extensions made informally by PRMan and BMRT over the years, put together in a single, clean document. iv Lecturers Larry Gritz is a co-founder and VP of Exluna, Inc., where he is the head of R&D for Entropy and BMRT. Larry was previously the head of the rendering research group at Pixar Animation Studios and chief architect of the RenderMan Interface Specification, as well as serving as a technical direc- tor on several film projects. His film credits include Toy Story, Geri’s Game, A Bug’s Life, Toy Story 2, and Monsters, Inc. Larry has a BS from Cornell University and MS and PhD degrees from the George Washington University. Larry co-wrote the book Advanced RenderMan: Creating CGI for Motion Pictures” (Morgan-Kaufmann, 1999), and has spoken at four previous SIGGRAPH courses on RenderMan (as course organizer for three of them). Matt Pharr is a co-founder and VP of Interactive Graphics at Exluna, Inc., where he has also con- tributed substantially to the design and implementation of the Entropy rendering architecture. He is expected to complete his Ph.D. in Computer Science at Stanford University in 2001. Matt has published three papers at SIGGRAPH in the past four years on topics of light scattering and render- ing of large scenes. He was a part-time member of Pixar’s Rendering R&D group from 1998-2000, contributing to development of PhotoRealistic RenderMan and next generation rendering architec- tures. He has a B.S degree in Computer Science from Yale University and an M.S. from Stanford; his movie credits include A Bug’s Life, Toy Story 2, and Monsters, Inc. Tony Apodaca is a senior technical director at Pixar Animation Studios. In the 20th century, he was director of Graphics R&D at Pixar, was co-creator of the RenderMan Interface Specification, and lead the development of PhotoRealistic RenderMan. Tony has been at Pixar since 1986, where his film credits include work from Red’s Dream through A Bug’s Life. He received a Scientific and Technical Academy Award from the Academy of Motion Picture Arts and Sciences for work on PhotoRealistic RenderMan, and with Larry was co-author of Advanced RenderMan: Creating CGI for Motion Pictures. He holds an MEng degree in computer and systems engineering from Rensselaer Polytechnic Institute. Christophe Hery is an Associate Visual Effects Supervisor at Industrial Light + Magic (ILM). Christophe joined ILM in 1993 as a senior technical director on The Flinstones. Prior to that, he was working for Acteurs Auteurs Associes (AAA) studio in France setting up a CG facility devoted to feature film production. Christophe majored in architecture and electrical engineering at ESTP, where he received his degree in 1989. While a student in Paris he freelanced as a technical director at BUF, as well as Thomson Digital Images, where he worked on 3-D software development in his spare time. After graduation, Christophe took a job as director of research and development at Label 35, a Parisian cartoon studio. Christophe is currently working as a CG supervisor on Jurassic Park 3. His numerous projects at ILM include Star Wars: Episode I: The Phantom Menace, Mission to Mars, Jumanji, Casper, The Mask, and many other films. Kevin Bjorke was the Lighting and Shading supervisor on Final Fantasy: The Spirits Within. Prior to Final Fantasy, he worked at a variety of studios in California, New York, and Europe, including Pixar and Digital Productions. He has collected three gold Clios for computer animation, and was one of the original off-site testers of Renderman, running it on an RM-1 board and rendering TV commercials on ChapReyes. Laurence Treweek is a senior technical director at Sony Pictures Imageworks. He has worked on many films including Hollow Man, Stuart Little, Stuart Little 2, and Contact. Brian Steiner is a senior technical director at Sony Imageworks, joining the company to work on Hollow Man and currently working on Stuart Little 2. Brian majored in computer animation at v Ringling School of Art & Design, and in 1994 came to Los Angeles to work for RezN.8 Productions. Since then he has worked at Boss Films Studios, Warner Bros., and Pacific Title. Some of Brian’s movie credits include Outbreak, Species, Batman Forever, Mars Attacks, and Duck Dodgers in the 21 Century. Douglas Sutton is a Lead Technical Director at Industrial Light + Magic(ILM). During his 4+ years at ILM he has worked on a variety of film projects including The Lost World, Flubber, Deep Impact, Star Wars: Episode I: The Phantom Menace, Galaxy Quest, Mission to Mars and A Perfect Storm. Previous to his work at ILM Doug worked at Will Vinton Studios in Portland Oregon and at Lamb and Co. in Minneapolis, Minnesota. He has a B.S. degree in Mechanical Engineering from the University of Minnesota and studied computer graphics as a graduate student at the U of M as well. vi vii Schedule Welcome and Introduction 8:30 AM Larry Gritz Interpreting PhotoRealistic RenderMan Statistics 8:45 AM Tony Apodaca A Practical Guide to Global Illumination 9:45 AM Larry Gritz Break 10:00 AM Global Illumination (continued) 10:15 AM Layered Media for Surface Shaders 11:00 AM Matt Pharr Lunch 12:00 PM A Tutorial on Procedural Primitives 1:30 PM Christophe Hery Using Maya with RenderMan on Final Fantasy 2:30 PM Kevin Bjorke Break 3:00 PM Maya+RenderMan on Final Fantasy (continued) 3:15 PM Volumetric Shaders Used In The Production Of Hollow Man 3:45 PM Lawrence Treweek Roundtable Discussion / Q&A 4:45 PM All panelists Finished — go to a party! 5:00 PM viii Contents Preface 1 1 Interpreting PRMan Statistics 3 1.1 Introduction . 3 1.2 Enabling Statistics Output . 3 1.3 Level 1 Statistics . 3 1.4 Level 2 Statistics . 6 1.5 Level 3 Statistics . 8 2 A Practical Guide to Global Illumination 11 2.1 Introduction: What is global illumination? . 11 2.2 Shadows . 13 2.3 Reflections . 18 2.4 Indirect illumination . 24 2.5 Caustics . 29 2.6 HDRI / Environment lighting . 34 2.7 References . 38 3 Layered Media for Surface Shaders 41 3.1 The Kubelka Munk Model . 41 3.2 The BRDF and Shading Language . 51 3.3 Subsurface Scattering . 54 3.4 Summary . 62 4 Procedural Primitives 63 4.1 Introduction . 63 4.2 Simple DRA Example . 63 4.3 Our original reason for using procedural RIB . 66 4.4 Other procedural RIB uses . 80 4.5 Let’s look at pictures . 84 5 Volumetric Shaders on Hollow Man 87 5.1 Goals . 87 5.2 Methods . 88 5.3 Why use RenderMan? . 89 5.4 Transforming Bones . 91 5.5 Rendering The Heart With Volumes . 97 ix x CONTENTS 6 Maya+RenderMan on Final Fantasy 115 6.1 Introduction . 115 6.2 Characters . 123 6.3 Shaders . 130 6.4 Credits . 159 6.5 Conclusion . 159 6.6 Listings . 161 Bibliography 173 Preface Welcome to Advanced RenderMan 3: Render Harder. (Okay, I was getting a little punchy when the submission deadline rolled around.) This course covers the theory and practice of using RenderMan and similar renderers to do the highest quality computer graphics animation production. This is the eighth SIGGRAPH course that we have taught on the use of RenderMan, and it is quite advanced. Students are expected to understand all of the basics of using RenderMan. We assume that you have all read the venerable RenderMan Companion, and certainly hope that you have attented our previous SIGGRAPH courses and read the book, Advanced RenderMan: Creating CGI for Motion Pictures (Morgan-Kaufmann, 1999).