MODELING, RENDERING and ANIMATING HUMAN HAIR By
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MODELING, RENDERING AND ANIMATING HUMAN HAIR by Tae-Yong Kim A Dissertation Presented to the FACULTY OF THE GRADUATE SCHOOL UNIVERSITY OF SOUTHERN CALIFORNIA In Partial Fulfillment of the Requirements of the Degree DOCTOR OF PHILOSOPHY (COMPUTER SCIENCE) December 2002 Copyright 2002 Tae-Yong Kim Doctoral Committee Form To be replaced with the actual form ii Acknowledgements It was a long journey to complete this thesis. The journey was truly adventurous and challenging. Sometimes there were exciting findings along the way, while other times I was so depressed and it seemed that I would never finish this journey. I must confess that without my advisor, Ulrich Neumann, I could have never escaped out of it. Whenever frustrations came, he was there to encourage me. Whenever new findings came out, he was there to congratulate. He is also the best listener I have met in my life. He was always the first person to understand my problems and ideas no matter how significant or insignificant they were. Even when it seemed that I had no clues for some problems, he never forced me his ideas, but discussed all the possibilities and better formulated the problem in his words. Often the times, I would find solutions just by talking to him, and it was a truly amazing experience. I deeply thank him for not only being the source of encouragements, but also teaching me how to become a real scholar and how to do research. I also would like to thank the other members of my thesis committee, Mathieu Desbrun and Jay Kuo. I am glad I could have them on my committee. Their suggestions and comments helped make this thesis complete and thorough. Through their scrutiny, I was able to evaluate and improve the thesis in totally different perspectives. Mathieu helped me understanding fundamental mathematical concepts, which can be priceless for my future research. I also would like to thank Ellis Horowitz and Ram Nevitia for serving as my qual committee. Ellis is an excellent teacher as well as a joyful racketball partner. Jay and Ram also helped me broadening my knowledge for graphics to images and vision in deeper level. Special thanks go to J.P. Lewis for his countless help. He is a good friend, an excellent researcher, and a source of virtually any help. His comments for my papers and thesis turned invaluable. His admirable knowledge set always makes me wish I could become such a competent scholar like him some time. I really enjoyed the life as a member of Computer Graphics and iii Immersive Technologies laboratory. As one of the early members of the lab, I have seen the lab growing into such a wonderful workplace. Dong Jin Cai, Ken Chen, Young Kwan Cho, Joe Demers, Jun Park, Ilmi Yoon were instrumental for me to find ways through the early stage of my study. Clint Chua, Reyes Enciso, Douglas Fidaleo, Junyong Noh, Bolan Jiang, and Jong Weon Lee have been excellent coworkers who helped me in some of the most critical stages. They are great individuals as well as researchers. Without their holistic supports, I could have never handled many critical problems. I also thank Anand Srinivasan for preparing all the lab equipments for me whenever necessary. I deeply thank my family for their unconditional love and supports. Without them, none of this would have been possible. My parents always had faiths in me, even when I had disbelief in myself. Without their continuous sacrifice, I would have never done what I present here. I appreciate for their patience, love, and encouragement for their youngest son. My brother and sister always connected deep moral supports although they were thousands miles away at times. I would like to dedicate this thesis to my father who sacrificed everything for us. This thesis is not only my achievement, but also his. iv Table of Contents Acknowledgements………………………………………………………………………………….ii List of Tables……...………………………………………………………………………………..vii List of Figures……………………………………………………………………………………..viii Abstract…………………………………………………………………………………………….xii 1. Introduction.................................................................................................................................... 1 1.1 Problem Statement .................................................................................................................. 2 1.2 Related Work .......................................................................................................................... 6 1.2.1 Surface Representation....................................................................................................6 1.2.2 Static Pose Hair and Texels............................................................................................. 7 1.2.4 Strand Based Model ........................................................................................................8 1.2.5 Key Hair Approach.......................................................................................................... 9 1.2.6 Discontinuous Cluster Model ........................................................................................ 10 1.2.7 Particles, Fluid flow, and Vector field........................................................................... 11 1.2.8 Hair Modeling from Photographs.................................................................................. 11 1.2.9 Hair Rendering .............................................................................................................. 12 1.2.10 Hair Animation............................................................................................................ 13 1.3 Thesis Overview.................................................................................................................... 14 2. Properties of Human Hair ............................................................................................................ 16 2.1 Properties of a Human Hair Fiber ......................................................................................... 16 2.2 Perception Based Analysis of Hair Photographs................................................................... 19 2.3 Artistic Drawings of Human Hair ......................................................................................... 20 2.4 Human Visual System........................................................................................................... 21 2.4.1 Contrast Sensitivity Function ........................................................................................ 21 2.4.2 Effect of Visual Masking............................................................................................... 22 2.5 Image Based Hair Rendering and Animation........................................................................ 23 2.6 Conclusion ............................................................................................................................ 24 3. Thin Shell Volume Modeling ...................................................................................................... 25 3.1 Shape Function...................................................................................................................... 26 3.1.1 Notation and Terminology............................................................................................. 27 3.1.2 TSV Generation and Volume Warping ......................................................................... 28 3.2 Virtual Hair Combing............................................................................................................ 29 3.2.1 Particle Selection (pickup)............................................................................................. 31 3.2.2 Particle Redistribution (s-direction) .............................................................................. 32 3.2.3 Sweeping Effect ............................................................................................................ 32 3.2.4 Vertical Motion (u-direction) ........................................................................................ 33 3.3 Rendering TSV...................................................................................................................... 34 3.3.1 Probabilistic Shadow Generation .................................................................................. 34 3.3.2 Shading and Antialiasing............................................................................................... 35 3.4 Implementation and Results..................................................................................................35 3.A Coons Patch.......................................................................................................................... 40 4. Interactive Multiresolution Hair Modeling and Editing............................................................... 41 4.1 Overview.............................................................................................................................. 43 4.2 Hair Cluster Representation .................................................................................................. 44 4.2.1 Generalized Cylinder..................................................................................................... 44 v 4.2.2 Representation of Contour............................................................................................. 46 4.2.3 Auxiliary Functions.......................................................................................................47 4.3 Scalp Surface........................................................................................................................