Bruce Merry
Abstract
Skeletal subspace deformation (SSD), a simple method of character animation used in many applications, has several shortcomings; the best-known being that joints tend to collapse when bent. We present animation space, a generalization of SSD that greatly reduces these effects and effectively eliminates them for joints that do not have an unusually large range of motion.While other, more expensive generalizations exist, ours is unique in expressing the animation process as a simple linear transformation of the input coordinates. We show that linearity can be used to derive a measure of average distance (across the space of poses), and apply this to improving parametrizations.Linearity also makes it possible to fit a model to a set of examples using least-squares methods. The extra generality in animation space allows for a good fit to realistic data, and overfitting can be controlled to allow fitted models to generalize to new poses. Despite the extra vertex attributes, it is possible to render these animation-space models in hardware with no loss of performance relative to SSD.
- Alexa, M. 2002. Linear combination of transformations. In SIGGRAPH: Proceedings of the 29th Annual Conference on Computer Graphics and Interactive Techniques. 380--387. Google Scholar
- Anguelov, D., Koller, D., Pang, H.-C., Srinivasan, P., and Thrun, S. 2004. Recovering articulated object models from 3D range data. In AUAI: Proceedings of the 20th Conference on Uncertainty in Artificial Intelligence. 18--26. Google Scholar
- Anguelov, D., Srinivasan, P., Koller, D., Thrun, S., Pang, H., and Davis, J. 2004. The correlated correspondence algorithm for unsupervised registration of nonrigid surfaces. In Proceedings of the Neural Information Processing Systems (NIPS) Conference.Google Scholar
- Collins, G. and Hilton, A. 2001. Modelling for character animation. Softw. Focus 2, 2, 44--51.Google Scholar
- Dominé, S. 2003. Mesh skinning. NVIDIA presentation. http://developer.nvidia.com/object/skinning.html.Google Scholar
- Eck, M., DeRose, T., Duchamp, T., Hoppe, H., Lounsbery, M., and Stuetzle, W. 1995. Multiresolution analysis of arbitrary meshes. In SIGGRAPH: Proceedings of the 22nd Annual Conference on Computer Graphics and Interactive Techniques. 173--182. Google Scholar
- Floater, M. S. and Hormann, K. 2004. Surface parameterization: A tutorial and survey. In Multiresolution in Geometric Modelling. N. A. Dodgson et al. eds. Springer-Verlag, New York.Google Scholar
- Golub, G. H. and Van Loan, C. F. 1996. Matrix Computations, 3rd ed. Johns Hopkins University Press, Baltimore, MD. Google Scholar
- James, D. L. and Twigg, C. D. 2005. Skinning mesh animations. ACM Trans. Graph. 24, 3, 399--407. Google Scholar
- Kavan, L. and Žára, J. 2005. Spherical blend skinning: A real-time deformation of articulated models. In SI3D: Proceedings of the Symposium on Interactive 3D Graphics and Games. 9--16. Google Scholar
- Kry, P. G., James, D. L., and Pai, D. K. 2002. Eigenskin: Real time large deformation character skinning in hardware. In Proceedings of the ACM SIGGRAPH/Eurographics Symposium on Computer Animation. 153--159. Google Scholar
- Lévy, B., Petitjean, S., Ray, N., and Maillot, J. 2002. Least squares conformal maps for automatic texture atlas generation. In Proceedings of the 29th Annual Conference on Computer Graphics and Interactive Techniques. 362--371. Google Scholar
- Lewis, J. P., Cordner, M., and Fong, N. 2000. Pose space deformation: A unified approach to shape interpolation and skeleton-driven deformation. In Proceedings of the 27th Annual Conference on Computer Graphics and Interactive Techniques. 165--172. Google Scholar
- Magnenat-Thalmann, N., Cordier, F., Seo, H., and Papagianakis, G. 2004. Modeling of bodies and clothes for virtual environments. In Proceedings of the 3rd International Conference on Cyberworlds (CW). 201--208. Google Scholar
- Magnenat-Thalmann, N., Laperrière, R., and Thalmann, D. 1988. Joint-Dependent local deformations for hand animation and object grasping. In Proceedings on the Graphics Interface Conference. 26--33. Google Scholar
- Mohr, A. and Gleicher, M. 2003. Building efficient, accurate character skins from examples. ACM Trans. Graph. 22, 3, 562--568. Google Scholar
- Mohr, A., Tokheim, L., and Gleicher, M. 2003. Direct manipulation of interactive character skins. In Proceedings of the Symposium on Interactive 3D Graphics. 27--30. Google Scholar
- Paige, C. C. and Saunders, M. A. 1982. LSQR: An algorithm for sparse linear equations and sparse least squares. ACM Trans. Math. Softw. 8, 1, 43--71. Google Scholar
- Ray, N. and Lévy, B. 2003. Hierarchical least squares conformal map. In Proceedings of the 11th Pacific Conference on Computer Graphics and Applications. 263--270. Google Scholar
- Sander, P. V., Snyder, J., Gortler, S. J., and Hoppe, H. 2001. Texture mapping progressive meshes. In Proceedings of the 28th Annual Conference on Computer Graphics and Interactive Techniques. 409--416. Google Scholar
- Sloan, P.-P. J., Rose, III, C. F., and Cohen, M. F. 2001. Shape by example. In Proceedings of the Symposium on Interactive 3D Graphics. 135--143. Google Scholar
- Stewart, D. and Leyk, Z. 1994. Meschach library version 1.2b. http://www.math.uiowa.edu/~dstewart/meschach/README.Google Scholar
- Wang, X. C. and Phillips, C. 2002. Multi-Weight enveloping: Least-Squares approximation techniques for skin animation. In Proceedings of the ACM SIGGRAPH/Eurographics Symposium on Computer Animation. 129--138. Google Scholar
Index Terms
- Animation space: A truly linear framework for character animation
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