“Collision-Free Construction ofAnimated Feathers Using 1mplicit Constraint Surfaces” by Weber and Gornowicz

We present a scheme for constructing complex feather geometry suitable for feature animation. The key points of our approach include the use of a potential field derived from guide geometry and an implicit constraint surface to create nonpenetrating feather geometry. Our method is frame independent and produces visually smooth animation that is free from popping and other visual artifacts. We provide details of the implementation and examples of the technique applied to an animated character with several thousand feathers.

1. Aitken, M., Butler, G., Lemmon, D., Saindon, E., Peters, D., and Williams, G. 2004. The lord of the rings: The visual effects that brought middle earth to the screen. In ACM SIGGRAPH 2004 Course Notes. ACM Press, New York, 11. 
2. Chen, Y., Xu, Y., Guo, B., and Shum, H.-Y. 2002. Modeling and rendering of realistic feathers. In Proceedings of SIGGRAPH. Computer Graphics Proceedings, Annual Conference Series, ACM, 630–636. 
3. Cohen, J., Varshney, A., Manocha, D., Turk, G., Weber, H., Agarwal, P., Brooks, F., and Wright, W. 1996. Simplification envelopes. In Proceedings of the 23rd Annual Conference on Computer graphics and Interactive Techniques. ACM, New York, 119–128. 
4. Cook, R. L. 1984. Shade trees. SIGGRAPH Comput. Graph. 18, 3, 223–231. 
5. Desbrun, M., Meyer, M., and Alliez, P. 2002. Intrinsic parameterizations of surface meshes. Eurograph. 21, 2.
6. Dong, C. and Wang, G. 2005. Surface reconstruction by offset surface filtering. J. Zhejiang University Sci., 6A.
7. Fletcher, R. 1987. Practical Methods of Optimization, 2nd ed. Wiley-Interscience, New York. 
8. Fordham, J. 2004. Something wicked this way comes. Cinefx, 99, 43–64.
9. Franco, C. G. and Walter, M. 2001. Modeling the structure of feathers. sibgrapi 00, 381. 
10. Hadap, S., Cani, M.-P., Lin, M., Kim, T.-Y., Bertails, F., Marschner, S., Ward, K., and Kačić-Alesić, Z. 2007. Strands and hair: Modeling, animation, and rendering. In ACM SIGGRAPH 2007 Courses. ACM, New York, 1–150. 
11. Kajiya, J. T. and Kay, T. L. 1989. Rendering fur with three dimensional textures. In Proceedings of the 16th Annual Conference on Computer Graphics and Interactive Techniques. ACM, New York, 271–280. 
12. Kaufman, D. and Chan, J. 2002. Stuart Little 2: Let the feathers fly. ACM SIGGRAPH 2002 Course Notes.
13. Neyret, F. 1998. Modeling, animating, and rendering complex scenes using volumetric textures. IEEE Trans. Visualiz. Comput. Graph. 4, 1, 55–70. 
14. Perrins, C. and Middleton, A. 1985. The Encyclopedia of Birds. Checkmark Books.
15. Porumbescu, S. D., Budge, B., Feng, L., and Joy, K. I. 2005. Shell maps. In Proceedings of the SIGGRAPH. ACM Press/ACM SIGGRAPH, Computer Graphics Proceedings, Annual Conference Series. ACM, 626–633. 
16. Robertson, B. and Aitken, M. 2004. The big and the smeagol. Comput. Graph. World 27, 1.
17. Sederberg, T. W., and Parry, S. R. 1986. Free-Form deformation of solid geometric models. SIGGRAPH Comput. Graph. 20, 4, 151–160. 
18. Streit, L. and Heidrich, W. 2002. A biologically-parameterized feather model. Comput. Graph. Forum 21, 3, 565–574.
19. Tong, Y., Lombeyda, S., Hirani, A. N., and Desbrun, M. 2003. Discrete multiscale vector field decomposition. ACM Trans. Graph. 22, 3, 445–452. 
20. Turk, G. 1992. Re-Tiling polygonal surfaces. In Proceedings of SIGGRAPH. ACM, vol. 26, 55–64. 
21. von Funck, W., Theisel, H., and Seidel, H.-P. 2006. Vector field based shape deformations. ACM Trans. Graph. 25, 3, 1118–1125. 
22. Wang, X., Tong, X., Lin, S., Hu, S., Guo, B., and Shum, H.-Y. 2004. Generalized displacement maps. In the Eurographics Symposium on Rendering. 
23. Wang, K., Weiwei, Tong, Y., Desbrun, M., and Schröder, P. 2006. Edge subdivision schemes and the construction of smooth vector fields. ACM Trans. Graph. 25, 3, 1041–1048.