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Art Directable Tornadoes ART DIRECTABLE TORNADOES A Thesis by RAVINDRA DWIVEDI Submitted to the Office of Graduate Studies of Texas A&M University in partial fulfillment of the requirements for the degree of MASTER OF SCIENCE May 2011 Major Subject: Visualization Art Directable Tornadoes Copyright 2011 Ravindra Dwivedi ART DIRECTABLE TORNADOES A Thesis by RAVINDRA DWIVEDI Submitted to the Office of Graduate Studies of Texas A&M University in partial fulfillment of the requirements for the degree of MASTER OF SCIENCE Approved by: Chair of Committee, Vinod Srinivasan Committee Members, John Keyser Wei Yan Head of Department, Tim McLaughlin May 2011 Major Subject: Visualization iii ABSTRACT Art Directable Tornadoes. (May 2011) Ravindra Dwivedi, B.E., Rajiv Gandhi Proudyogiki Vishwavidyalaya Chair of Advisory Committee: Dr. Vinod Srinivasan Tornado simulations in the visual effects industry have always been an interesting problem. Developing tools to provide more control over such effects is an important and challenging task. Current methods to achieve these effects use either particle systems or fluid simulation. Particle systems give a lot of control over the simulation but do not take into account the fluid characteristics of tornadoes. The other method which involves fluid simulation models the fluid behavior accurately but does not give control over the simulation. In this thesis, a novel method to model tornado behavior is presented. A tool based on this method was also created. The method proposed in this thesis uses a hybrid approach that combines the flexibility of particle systems while producing interesting swirling motions inherent in the fluids. The main focus of the research is on providing easy-to-use controls for art directors to help them achieve the desired look of the simulation effectively. A variety of controls is provided which include the overall shape, path, rotation, debris, surface, swirling motion, and interaction with the environment. The implementation was done in Houdini, which is a 3D animation software whose node based system allows an algorithmic approach to the problem and integrates well with the current tools. The tool allows the user to create iv animations that reflect the visual characteristics of real tornadoes. The usefulness of the tool was evaluated among participants who had some experience in 3D animation software. The results from the simulation and evaluation feedback reveal that the tool successfully allowed the users to create tornadoes of their choice efficiently. v DEDICATION I dedicate this thesis to my family. vi ACKNOWLEDGEMENTS I would like to thank my committee chair, Dr. Vinod Srinivasan and my committee members, Dr. John Keyser and Dr. Wei Yan for their guidance and support throughout the course of this thesis. Special thanks to Dale Mayeda and Rob Dressel for their inputs during the preliminary stages of the research and their feedback during the later stages which helped refine the tool. Thanks, also, to the Head of the Department, Tim McLaughlin, for his encouragement and to my colleagues, in the Department of Visualization at Texas A&M University, for their support. I also want to extend my gratitude to the participants who helped in the evaluation of the tool. To my mother and father, I cannot thank you enough for your patience and love and making me a person I am today. I am grateful to my brother, Ajendra and sister, Pooja, for boosting my confidence and being supportive. I am very appreciative to my brother-in-law, C.P. Tiwari, for not only supporting my education but also encouraging me. Thank you to all the family members for their love. I will always be grateful to the teachers and staff of my boarding school, Rajkumar College, Raipur, where I learned the importance of education. Finally, a special thanks to all my friends for being an important part of my life. vii TABLE OF CONTENTS Page ABSTRACT .............................................................................................................. iii DEDICATION .......................................................................................................... v ACKNOWLEDGEMENTS ...................................................................................... vi TABLE OF CONTENTS .......................................................................................... vii LIST OF FIGURES ................................................................................................... x CHAPTER I INTRODUCTION ................................................................................ 1 II BACKGROUND, RELATED WORK ................................................ 3 II.1. Motivation .............................................................................. 3 1. Need for Art-Directed Simulations ............................... 3 II.2. Tornado and Its Characteristics .............................................. 6 1. Description .................................................................... 6 2. Color .............................................................................. 7 3. Path ................................................................................ 8 4. Rotational Direction ...................................................... 8 5. Shapes ............................................................................ 8 6. Types ............................................................................. 10 II.3. Tornado Dynamics ................................................................. 11 II.4. Existing Simulations ............................................................... 14 III METHODOLOGY ............................................................................... 18 III.1. Visual Inspiration .................................................................. 18 1. Features ......................................................................... 18 2. Shapes ............................................................................ 21 III.2. Design .................................................................................... 24 1. Metaball ......................................................................... 25 2. Directional Force ........................................................... 26 3. Vortex Force .................................................................. 26 4. Lattice ............................................................................ 27 viii CHAPTER Page 5. Fluid Simulation ............................................................ 28 III.3. Particle System ...................................................................... 30 1. Animatable Curve ......................................................... 30 2. Particle Emitter .............................................................. 32 3. Funnel Force Fields ....................................................... 33 4. Deforming Particles ....................................................... 35 5. Tornado Surface ............................................................ 36 6. Debris Emitter & Forces ............................................... 37 III.4. Fluids ..................................................................................... 40 1. Scalar Fields .................................................................. 40 2. Particles as Sources ....................................................... 40 IV IMPLEMENTATION .......................................................................... 47 IV.1. Side Effects Houdini ............................................................. 47 IV.2. Houdini Digital Asset ............................................................ 47 IV.3. Simulation ............................................................................. 49 1. Particles ......................................................................... 49 2. Smoke ............................................................................ 55 3. Lighting, Rendering & Shading .................................... 59 4. Lightning ....................................................................... 60 IV.4. Fracturing and Debris ............................................................ 61 1. Seed Points .................................................................... 61 2. Particle Driven ............................................................... 64 IV.5. Tool ....................................................................................... 66 1. Python Scripting ............................................................ 66 V EVALUATION ..................................................................................... 68 V.1. Results .................................................................................... 68 1. Qualitative Study ........................................................... 68 V.2. Limitations of Study ............................................................... 74 VI CONCLUSIONS AND FUTURE WORK ........................................... 76 VI.1. Summary ............................................................................... 76 VI.2. Future Work .......................................................................... 77 REFERENCES .......................................................................................................... 80 ix CHAPTER Page APPENDIX A ........................................................................................................... 83 VITA ........................................................................................................................
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