Real-time enveloping with rotational regression

ABSTRACT

Enveloping, or the mapping of skeletal controls to the deformations of a surface, is key to driving realistic animated characters. Despite its widespread use, enveloping still relies on slow or inaccurate deformation methods. We propose a method that is both fast, accurate and example-based. Our technique introduces a rotational regression model that captures common skinning deformations such as muscle bulging, twisting, and challenging areas such as the shoulders. Our improved treatment of rotational quantities is made practical by model reduction that ensures real-time solution of least-squares problems, independent of the mesh size. Our method is significantly more accurate than linear blend skinning and almost as fast, suggesting its use as a replacement for linear blend skinning when examples are available.

REFERENCES

• 1: Allen, B., Curless, B., Popović, Z., and Hertzmann, A. 2006. Learning a correlated model of identity and pose-dependent body shape variation for real-time synthesis. In Symposium on Computer Animation, 147--156.
• 2: Anguelov, D., Srinivasan, P., Koller, D., Thrun, S., Rodgers, J., and Davis, J. 2005. SCAPE: shape completion and animation of people. ACM Trans. Graph. 24, 3 (Aug.), 408--416.
• 3: Capell, S., Green, S., Curless, B., Duchamp, T., and Popović, Z. 2002. Interactive skeleton-driven dynamic deformations. ACM Trans. Graph. 21, 3 (July), 586--593.
• 4: Capell, S., Burkhart, M., Curless, B., Duchamp, T., and Popović, Z. 2005. Physically based rigging for deformable characters. In Symposium on Computer Animation, 301--310.
• 5: cgCharacter, 2003. Absolute character tools 1.6. www.cgcharacter.com.
• 6: Cohen-Steiner, D., Alliez, P., and Desbrun, M. 2004. Variational shape approximation. ACM Trans. Graph. 23, 3 (Aug.), 905--914.
• 7: Comet, M., 2006. Cmusclesystem 1.31. www.cometdigital.com.
• 8: Der, K. G., Sumner, R. W., and Popović, J. 2006. Inverse kinematics for reduced deformable models. ACM Trans. Graph. 25, 3 (July), 1174--1179.
• 9: Diebel, J. R., Thrun, S., and Brünig, M. 2006. A bayesian method for probable surface reconstruction and decimation. ACM Trans. Graph. 25, 1 (Jan.), 39--59.
• 10: Eggert, D. W., Lorusso, A., and Fisher, R. B. 1997. Estimating 3-d rigid body transformations: a comparison of four major algorithms. Mach. Vision Appl. 9, 5--6, 272--290.
• 11: Guo, Z., and Cheong Wong, K. 2005. Skinning With Deformable Chunks. Computer Graphics Forum 24, 3, 373--381.
• 12: Hargreaves, S. 2004. Deferred shading. In Proceedings of the Game Developers Conference.
• 13: Hyun, D.-E., Yoon, S.-H., Chang, J.-W., Seong, J.-K., Kim, M.-S., and Jüttler, B. 2005. Sweep-based human deformation. The Visual Computer 21, 8--10, 542--550.
• 14: James, D. L., and Twigg, C. D. 2005. Skinning mesh animations. ACM Trans. Graph. 24, 3, 399--407.
• 15: Karni, Z., and Gotsman, C. 2004. Efficient compression of soft-body animation sequences. Computer and Graphics 28, 1 (Feb.), 25--34.
• 16: Kavan, L., and Žára, J. 2005. Spherical blend skinning: a real-time deformation of articulated models. In Symposium on Interactive 3D Graphics and Games, 9--16.
• 17: Kry, P. G., James, D. L., and Pai, D. K. 2002. EigenSkin: real time large deformation character skinning in hardware. In Symposium on Computer Animation, 153--159.
• 18: Lee, M. 2006. Seven ways to skin a mesh: Character skinning revisited for modern GPUs. In Proceedings of GameFest, Microsoft Game Technology Conference.
• 19: Lewis, J. P., Cordner, M., and Fong, N. 2000. Pose space deformations: A unified approach to shape interpolation and skeleton-driven deformation. In Proceedings of ACM SIG-GRAPH 2000, Computer Graphics Proceedings, Annual Conference Series, 165--172.
• 20: Merry, B., Marais, P., and Gain, J. 2006. Animation space: A truly linear framework for character animation. ACM Trans. Graph. 25, 4 (Oct.), 1400--1423.
• 21: Mohr, A., and Gleicher, M. 2003. Building efficient, accurate character skins from examples. ACM Trans. Graph. 22, 3 (July), 562--568.
• 22: Rhee, T., Lewis, J., and Neumann, U. 2006. Real-time weighted pose-space deformation on the GPU. Computer Graphics Forum 25, 3 (Sept.), 439--448.
• 23: Scheepers, F., Parent, R. E., Carlson, W. E., and May, S. F. 1997. Anatomy-based modeling of the human musculature. In Proceedings of SIGGRAPH 97, Computer Graphics Proceedings, Annual Conference Series, 163--172.
• 24: Sloan, P.-P. J., Charles F. Rose, I., and Cohen, M. F. 2001. Shape by example. In Symposium on Interactive 3D Graphics and Games, 135--143.
• 25: Sumner, R. W., and Popović, J. 2004. Deformation transfer for triangle meshes. ACM Trans. Graph. 23, 3, 399--405.
• 26: Sumner, R. W., Zwicker, M., Gotsman, C., and Popović, J. 2005. Mesh-based inverse kinematics. ACM Trans. Graph. 24, 3, 488--495.
• 27: Teran, J., Sifakis, E., Irving, G., and Fedkiw, R. 2005. Robust quasistatic finite elements and flesh simulation. In Symposium on Computer Animation, 181--190.
• 28: Wang, X. C., and Phillips, C. 2002. Multi-weight enveloping: Least-squares approximation techniques for skin animation. In Symposium on Computer Animation, 129--138.
• 29: Weber, J. 2000. Run-time skin deformation. In Proceedings of Game Developers Conference.
• 30: Wilhelms, J., and Gelder, A. V. 1997. Anatomically based modeling. In Proceedings of SIGGRAPH 97, Computer Graphics Proceedings, Annual Conference Series, 173--180.

INDEX TERMS

Primary Classification:
  I. Computing Methodologies
  I.3 COMPUTER GRAPHICS
      I.3.7 Three-Dimensional Graphics and Realism
          Subjects: Animation

Additional Classification:
  I. Computing Methodologies
  I.6 SIMULATION AND MODELING
      I.6.8 Types of Simulation
          Subjects: Animation

Keywords:
animation, deformation, enveloping, model reduction, skinning