Efficient Collision Detection for Spherical Blend Skinning

Ladislav Kavan
CTU in Prague
Trinity College Dublin
Carol O'Sullivan
Trinity College Dublin
Jiří Žára
CTU in Prague

(a) shoulder twist deformed by linear blend skinning produces the candy-wrapper artifact, (b) bounding spheres for linear blend skinning refitted by [Kavan and Zara 2005a], (c) the same posture deformed by spherical blend skinning [Kavan and Zara 2005b], (d) bounding spheres for spherical blend skinning refitted using the algorithm introduced in this paper. Efficient refitting of bounding spheres is a crucial component of our fast collision detection algorithm.


Recently, two algorithms improving the real time simulation of articulated models in virtual environments have been published: fast collision detection for linear blend skinning and spherical blend skinning. Both linear and spherical blending solve the skinning problem of a skeletally controlled 3D model (e.g., an avatar), but only spherical blending avoids artifacts such as the candywrapper. However, to date, fast collision detection has been limited to linear blending. This paper describes how to perform collision detection for models skinned with the more sophisticated spherical method. As a result, both high-quality skinning and fast and exact collision detection can be achieved - there is no longer any need for a trade-off. The generalization from linear to spherical blending involves the construction of rotation bounds, derived using a quaternion representation. The resulting algorithm is simple to implement and fast enough for real-time virtual reality applications.


Ladislav Kavan, Carol O'Sullivan, Jiří Žára. Efficient Collision Detection for Spherical Blend Skinning. Graphite (4th International Conference on Computer Graphics in Australasia and South-East Asia), 2006.  

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This work has been partly supported by the Ministry of Education of the Czech Republic under the research programs LC-06008 (Center for Computer Graphics) and MSM 6840770014. We also thank the anonymous reviewers for their valuable suggestions and Ŝtĕpán Prokop for donating his 3D models.