ADVANCE PROGRAM SUBMISSION Course 16 Particle System Modeling, Animation, and Physically-Based Techniques level: intermediate/full-day when: Tuesday course description: Particle systems have been used to model phenomena as diverse as fire and snow, grass and drifting leaves, liquid and draping cloth. In this course we will move from a retrospective on particle-system animation, to a tutorial on some of the latest results in the use of physically-based techniques to model highly complex materials and phenomena. We will contrast particle system modeling with surface based techniques, and will show how particles can be used at several levels of detail in choreographing an animation. Examples of state-of-the-art work incorporating particle-particle interactions will range from a paradigm for modeling heat-dependent fluid-flow, to a model for the automatic choreography of the draping behavior of woven cloth. Presentations will be illustrated with examples from a series of memorable films and recent test animations from the laboratory. course objectives: The course will be both a thorough tutorial on the particle-system modeling approach, and an introduction to some of the latest work in modeling highly complex phenomena using systems of mutually interacting particles. Students should come away with enough background to incorporate particle-system simulations and tools into their own work, and will develop a feel for the range of phenomena amenable to modeling with particles. recommended background/difficulty: Students should have a working knowledge of modeling and rendering techniques for computer graphics, and feel comfortable with the fundamental ideas of calculus and physics. who should attend: Implementers, researchers, and educators who are interested in both the latest developments in the use of particle systems for the modeling of highly deformable materials, and in the progression of ideas, techniques, and experiences that lead to the current state of the art. course chair: Donald H. House, Williams College lecturers in order of presentation: William Reeves, PIXAR David Haumann, IBM T.J. Watson Research Center Donald H. House, Williams College David Tonnesen, U of Toronto/DEC Cambridge Research David E. Breen, Rensselaer Polytechnic Institute chair biography: Donald House is an Associate Professor of Computer Science at Williams College, and a Visiting Research Scientist at the Rensselaer Design Research Center. He holds a Bachelors Degree in Mathematics from Union College, a Masters in Electrical Engineering from Rensselaer, and a PhD in Computer Science from the University of Massachusetts. He had a ten year industrial career in process and industrial automation, and pursued early research interests in Computational Neuroscience, investigating the computational strategies of depth perception in frogs and toads. His current work is in computer graphics and animation, focusing on particle-based physical models of complex materials. He is a member of ACM and SIGGRAPH. PRESENTATIONS An Introduction to Particle Systems -- William Reeves Bill Reeves will contrast particle system modeling and rendering with surface based techniques, and will show the power of the particle-system approach for a large class of problems. He will present a retrospective of his early work on particle systems, illustrated by their use in such well known animations as "Star Trek II: The Wrath of Kahn", "The Adventures of Andre and Wally B.", "Red's Dream", "Flags and Waves, and "Knickknack". Physically-based Particle System Choreography -- David Haumann Dave Haumann will show how particles can be used at several levels of detail in choreographing an animation. Simple single particles can be used to approximate the translational motion of larger objects in response to a surrounding flow field. Once translational motion is deemed satisfactory by the animator, the simple particles can be replaced by more highly detailed objects consisting of several interconnected particles. These can undergo more complex motion due to surface-field interactions. By using particles to construct physical objects with two or more levels of "physical" detail, it is possible to choose the level of "motion" detail exhibited in the resulting animation. These techniques will be illustrated as they were applied in the production of the film "Leaf Magic", in which particles were used to develop a physically-based model of Autumn leaves blowing in the wind. Coupled Particle Systems -- Donald House When the particles in a system are coupled together so that they interact with and affect each other, the particle system takes on macroscopic characteristics that emerge from the aggregation of these microscopic interactions. Donald House will set the stage for the final two speakers, who will present their experiences in developing and working with coupled particle system models. He will begin by outlining the potential uses of particle systems for the modeling of complex and sometimes ill understood materials, and will describe techniques for developing such a model. He will then address the computational challenges inherent in solving the many-body problem resulting from particle coupling, and describe algorithms and techniques to deal with these challenges. Coupled Dynamics, Modeling, and Rendering -- David Tonnesen David Tonnesen will present his experiences in applying spatially symmetric and asymmetric energy fields to dynamically connected particle systems. Particle systems exhibit a wide range of behavior based on the structure of the energy fields acting between the particles. Spatially symmetric energy fields are appropriate for the dynamic modeling of volumes, while spatially asymmetric fields can be applied to the modeling of surfaces. He will describe his work with symmetric energy fields, with examples of fluid flow and a heat-dependent modeling paradigm useful for animation. Asymmetric fields will be described as used in an interactive surface modeling tool and a physically based approach for extracting surfaces of variable topology from 3D data. This session will conclude with a discussion of algorithms for mapping particle systems to surfaces suitable for rendering, and related rendering issues. A Particle-Based Dynamic Model of Cloth -- David Breen David Breen will discuss his recent work in developing a computational model of woven cloth that can be used to choreograph its draping behavior. Many of the important interactions that determine the behavior of plain woven fabric occur at the point where threads cross. Given that thread crossings play such an important role in influencing the local behavior of cloth, the model treats the thread crossings as the fundamental modeling unit, or particle. Constraints acting at the level of these particles are maintained on the relationships between the threads. The details of the cloth model will be presented, emphasizing how the modeling of the low level structure of cloth produces characteristic cloth-like draping and folding at the large scale. The evaluation technique used to perform the draping simulation will be discussed in detail in order to assist those attendees interested in implementing a similar model. Speaker Biographies Chair Donald H. House Associate Professor Department of Computer Science Williams College Williamstown, MA 01267 house@cs.williams.edu Donald House is an Associate Professor of Computer Science at Williams College, and a Visiting Research Scientist at the Rensselaer Design Research Center. He earned a Bachelors Degree in Mathematics from Union College in 1969, a Masters in Electrical Engineering from Rensselaer in 1978, and a PhD in Computer Science from the University of Massachusetts in 1984. He had a ten year industrial career with the General Electric Company in process and industrial automation, and pursued early research interests in Computational Neuroscience, investigating the computational strategies of depth perception in frogs and toads. His current work is in computer graphics and animation, focusing on particle-based physical models of complex materials. He is a member of ACM and SIGGRAPH. ******************************************************************** David E. Breen Research Engineer Rensselaer Design Research Center CII 7015 Rensselaer Polytechnic Institute Troy, NY 12180-3590 david@rdrc.rpi.edu David Breen is a Research Engineer and a PhD Candidate in and Computer and Systems Engineering at Rensselaer Polytechnic Institute. He received an AB in Physics from Colgate University in 1982, and an MS in Computer and Systems Engineering from Rensselaer in 1985. He has been on the full-time research staff of the Rensselaer Design Research Center since 1985, where he is the co-leader of the Visual Technologies Program. From August 1987 to July 1988 he was a visiting research engineer at Zentrum fuer Graphische Datenverarbeitung in Darmstadt, Germany. His research interests include particle-based modeling, computer animation, volume data analysis and object-oriented computer graphics. Breen co-lead the team that developed the object-oriented animation system, The Clockworks. He is a member of ACM SIGGRAPH, the IEEE Computer Society, the Computer Graphics Society, and the Fiber Society. *************************************************************** David R. Haumann Research Staff Member IBM T. J. Watson Research Yorktown Heights New York 10598 haumann@watson.ibm.com David R. Haumann is currently a Research Staff Member at IBM T. J. Watson Research Center in Yorktown Heights, N.Y. He received his Ph.D. in Computer Science at The Ohio State University in 1989, and his B.S. in Applied Mathematics from Brown University in 1977. His experience in computer graphics spans the fields of radiation treatment planning, flight simulation and commercial computer animation production. His research interests include computer graphics, animation, and physically-based modeling. His animation techniques have been featured in the award winning SIGGRAPH films "Dynamic Simulations of Flexible Objects", "Balloon Guy" and "Leaf Magic", and he has contributed to several others, including "Broken Heart" and "Dirty Power". David is a member of Phi Kappa Phi Honor Society, ACM (SIGGRAPH) and IEEE. ************************************************************* William T. Reeves Head of Animation Research and Development Pixar 1001 West Cutting Blvd Richmond CA 94804 pixar!bill@uu.psi.com Bill studied mathematics at the University of Waterloo in Canada and received his B. Math in 1974. He then went to the University of Toronto and received a Msc. Computer Science in 1976, and a PhD. in 1980. Bill's masters research studied the implementation of interactive computer graphics in a mini-computer environment. His doctoral research studied representations of complex dynamic shape for computer animation and motion analysis. The motion analysis work was to aid in cardiovascular research. This work also led to some new techniques for computer based inbetweening that was published in ACM SIGGRAPH in 1981. In 1980, Bill joined the Computer Division of Lucasfilm as project leader of the systems group and a member of the computer graphics group. From 1982 to 1986, he worked full time in the graphics group as project leader of the modelling and animation team. In 1982, Bill invented a new image synthesis technique called particle systems that enables the generation of very complex and detailed images. It has been used to model fire, fireworks, trees, grass, and flowers. This research was published by ACM SIGGRAPH in 1983 and in 1985. In 1986, Bill left Lucasfilm along with most of the rest of the Computer Division and joined Pixar as head of Animation Research and Development. Also in 1986, Bill published with Alain Fournier a paper presenting a simple computer graphics model of ocean waves which has led to some very realistic images. With coauthors, David Salesin and Rob Cook, Bill published a paper in 1987 detailing a new shadow algorithm to efficiently compute anti-aliased shadows. Bill's film credits while at Lucasfilm and Pixar include: "Star Trek II: The Wrath of Khan", "Return of the Jedi", "The Adventures of Andre and Wally B.", "Young Sherlock Holmes", "Blowin' in the Wind", "Flags and Waves", "Luxo Jr." (1986 Academy Award nominee), "Red's Dream", "Tin Toy" and "Knickknack". In 1988, Bill received an Academy Award for Best Animated Short Film for his work as Technical Director on "Tin Toy". ******************************************************************* David Tonnesen Research Assistant Dept. of Computer Science 10 King's College Road University of Toronto Toronto, Canada, M5S 1A4 davet@dgp.toronto.edu David is a research assistant and a PhD Candidate in Computer Graphics at the University of Toronto. He is also a consultant for DEC Cambridge Research Laboratory. He received a Masters in Computer Science from Rensselaer Polytechnic Institute in 1989, and also earned two Bachelor degrees from Washington University, St. Louis, Missouri, in 1983; one in Electrical Engineering and the other in Computer Science. He has worked in the Neuroanatomical Image Processing Facility at Washington University's School of Medicine and at Rockwell International Space System Division's Space Shuttle Flight Simulation Laboratory. He has held summer positions at Cray Research and Lawrence Livermore National Laboratory NMFECC. His research interests include computer graphics, animation, physically based modeling, and surface reconstruction techniques. He is a member of IEEE and ACM.