程序式動畫是一種根據使用者所提供的高階運動參數，自動產生動畫的方法。藉著高階的運動參數，程序式動畫比運動擷取資料有著更高的彈性。使用者可透過調整參數，輕易地讓動畫滿足情境上所需的限制。但如何調整適當的運動參數以產生擬真的動畫仍屬不易，因此程序式動畫常有在視覺上觀感不自然的問題。本研究的目標是，將運動擷取資料擬真的要素，帶到程序式動畫之中，以改進程序式動畫的品質。我們將問題定義成一個最佳化問題：給定一段運動擷取資料，系統該如何調整程序式動畫之參數，使得程序式動畫與運動擷取資料的差距盡可能地縮小？我們的系統可以參考一段運動擷取資料，以最佳化演算法，自動調整程序式動畫的參數，搜尋能產生出與運動擷取資料最為相似的運動參數。為了進一步讓產生之動畫符合環境的限制需求，多組最佳化過後的運動參數可以再透過內插，重新產生出一組符合限制需求的運動參數。實驗結果顯示，我們的方法不但使程序式動畫得以保留原來彈性的優點，也改善了程序式動畫常有的視覺觀感不自然的缺點。

Procedural animation provides a way for a user to generate animation according to the high-level motion parameters that the user supplies. With the high-level motion parameters, procedural animation has the flexibility of generating animation accommodating the requested constraints in a scenario. However, tuning parameters to generate realistic animations usually is a difficult task. Therefore, animations produced with this approach often have the drawback of unrealistic-looking. Our goal is to improve the quality of procedural animation by bringing the naturalness of motion capture data into procedural animation. We model our problem as an optimization problem: given a motion captured clip, how does the system tune the motion parameters in an animation procedure to minimize the difference between animations produced by a procedure and captured in a motion clip? Our proposed system takes a motion captured clip as a reference and tunes the motion parameters of the animation procedure with an optimization algorithm. In order to generate animation satisfying environmental constraints, multiple optimized motion parameters can be interpolated to create a new set of motion parameters which can also satisfy the constraints. Our experimental results show that our method not only retains the flexibility of procedural animation, but also enhances the quality of procedural animation.

[1] R. Boulic, N. Magnenat-Thalmann, and D. Thalmann, “A Global Human Walking Model with Real-Time Kinematic Personification,” in Visual Computer, Vol.6, Issue.6, p.344-358, 1990.
[2] A. Bruderlin and T. Calvert, “Goal-Directed, Dynamic Animation of Human Walk-ing,” in Proceedings of the 16th Annual Conference on Computer Graphics and Inter-active Techniques, p.233-242, 1989.
[3] A. Bruderlin and T. Calvert, “Knowledge-Driven, Interactive Animation of Human Running,” in Proceedings of the Conference on Graphics Interface ’96, p.213-221, 1996.
[4] A. Bruderlin and L. Williams, “Motion Signal Processing,” in Proceedings of the 22nd Annual Conference on Computer Graphics and Interactive Techniques, p.97-104, 1995.
[5] P.F. Chen and T.Y. Li, “Generating Humanoid Lower-Body Motions with Real-Time Planning,” in Proceedings of Computer Graphics Workshop 2002, 2002.
[6] D. Chetverikov and Z. Szabo, “A Simple and Efficient Algorithm for Detection of High Curvature Points in Planar Curves,” in Proceedings of 23rd Workshop of the Austrian Pattern Recognition Group, p.175-184, 1999.
[7] S. Coros, P. Beaudoin, K.K. Yin, and M. van de Pann, “Synthesis of Constrained Walking Skills,” in ACM Transactions on Graphics, Vol.27, Issue.5, 2008.
[8] P. Faloutsos, M. van de Panne, and D. Terzopoulos, “Composable Controllers for Physics-Based Character Animation,” in Proceedings of the 28th Annual Conference on Computer Graphics and Interactive Techniques, p.251-260, 2001.
[9] P. Glardon, R. Boulic, and D. Thalmann, “PCA-Based Walking Engine Using Motion Capture Data,” in Proceedings of the Computer Graphics International, p.292-298, 2004.
[10] M. Gleicher, “Retargetting Motion to New Characters,” in Proceedings of the 25th Annual Conference on Computer Graphics and Interactive Techniques, p.33-42, 1998.
[11] C. Hecker, B. Raabe, R.W. Enslow, J. Deweese, J. Maynard, and K. van Prooijen, “Real-Time Motion Retargeting to Highly Varied User-Created Morphologies,” in ACM Transactions on Graphics, Vol.27, Issue.3, 2008.
[12] J.K. Hodgins, W.L. Wooten, D.C. Brogan, and J.F. O’Brien, “Animating Human Ath-letics,” in Proceedings of the 22nd Annual Conference on Computer Graphics and In-teractive Techniques, p.71-78, 1995.
[13] S. Kirkpatrick, C.D. Gelatt, and M.P. Vecchi, “Optimization by Simulated Annealing,” in Science, Vol.220, p.671-680, 1983.
[14] L. Kovar, M. Gleicher, and F. Pighin, “Motion Graphs,” in ACM Transactions on Graphics, Vol.21, Issue.3, p.473-482, 2002.
[15] T. Kwon and S.Y. Shin, “Motion Modeling for On-Line Locomotion Synthesis,” in Proceedings of the 2005 ACM SIGGRAPH/Eurographics Symposium on Computer Animation, p. 29-38, 2005.
[16] C.H. Liang and T.Y. Li, “Simulating Human Low-Posture Motions with Procedural Animation,” in Proceedings of Computer Graphics Workshop 2007, 2007.
[17] C.H. Liang, P.C. Tao, and T.Y. Li, “IMHAP – An Experimental Platform for Human-oid Procedural Animation,” in Proceedings of the 3rd International Conference on In-ternational Information Hiding and Multimedia Signal Processing, Vol.1, p.345-348, 2007.
[18] F. Multon, L. France, L., M-P. Cani, and G. Debunne, “Computer Animation of Human Walking: a Survey,” in Journal of Visualization and Computer Animation, Vol.10, p39-54, 1999.
[19] K. Perlin, “An Image Synthesizer,” in ACM SIGGRAPH Computer Graphics, Vol.19, Issue.3, p287-296, 1985.
[20] K. Perlin, “Real Time Responsive Animation with Personality,” in IEEE Transactions on Visualization and Computer Graphics, Vol.1, Issue.1, p.5-15, 1995.
[21] K. Perlin, “Building Virtual Actors Who Can Really Act,” in Proceedings of the 2nd International Conference on Virtual Storytelling, p.127-134, 2003.
[22] C. Rose, B. Guenter, B. Bodenheimer, and M.F. Cohen, “Efficient Generation of Mo-tion Transitions Using Spacetime Constraints,” in Proceedings of the 23rd Annual Conference on Computer Graphics and Interactive Techniques, p.147-154, 1996.
[23] S.J. Russell and P. Norvig, “Simulated Annealing Search,” in Artificial Intelligence: A Modern Approach (2nd Edition), Prentice Hall, p.115-116, 2002.
[24] A. Safonova and J.K. Hodgins, “Construction and Optimal Search of Interpolated Mo-tion Graphs,” in ACM Transactions on Graphics, Vol.26, Issue.3, 2007
[25] A. Shapiro, Y. Cao, and P. Faloutsos, “Style Components,” in Proceedings of Graphics Interface 2006, p. 33-39, 2006.
[26] K. Sims, “Evolving Virtual Creatures,” in Proceedings of the 21st Annual Conference on Computer Graphics and Interactive Techniques, p.15-22, 1994.
[27] K.W. Sok, M. Kim, and J. Lee, “Simulating Biped Behaviors from Human Motion Data,” in ACM Transactions on Graphics, Vol.26, Issue.3, 2007.
[28] H.C. Sun and D.N. Metaxas, “Automating Gait Generation,” in Proceedings of the 28th Annual Conference on Computer Graphics and Interactive Techniques, p.261-270, 2001.
[29] M. Thorne, D. Burke, M. van de Panne, “Motion Doodles: An Interface for Sketching Character Motion,” in ACM Transactions on Graphics, Vol.23, Issue.3, p.424-431, 2004.
[30] D. Tolani, A. Goswami, N.I. Badler, “Real-Time Inverse Kinematics Techniques for Anthropomorphic Limbs,” in Graphical Models and Image Processing, Vol.62, Is-sue.5, p.353-388, 2000.
[31] M. van de Panne, “From Footprints to Animation,” in Computer Graphics Forum, Vol.16, No.4, p.211-223, 1997.
[32] R. Williams, The Animator's Survival Kit. Faber & Faber, 2002.
[33] A. Witkin and M. Kass, “Spacetime Constraints,” in Proceedings of the 15th Annual Conference on Computer Graphics and Interactive Techniques, p.159-168, 1988.
[34] A. Witkin and Z. Popovic, “Motion Warping,” in Proceedings of the 22nd Annual Conference on Computer Graphics and Interactive Techniques, p.105-108, 1995.
[35] D. Zeltzer, “Motion Control Techniques for Figure Animation,” in IEEE Computer Graphics and Applications, Vol.2, Issue.9, p.53-59, 1982.
[36] CMU Motion Capture Database: http://mocap.cs.cmu.edu
[37] Humanoid Animation Working Group (H-Anim): http://www.h-anim.org
[38] jMonkey Engine: http://www.jmonkeyengine.com
[39] Model-View-Controller, http://en.wikipedia.org/wiki/Model-view-controller
[40] Motion Capture Systems from Vicon: http://www.vicon.com
[41] Setting Up an Inverse Foot: http://www.kurgan.dk/mayafaq/faq2.html
[42] Voronoi/Delaunay Applet: http://www.cs.cornell.edu/home/chew/Delaunay.html