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Section: Software

MKM : Manageable Kinematic Motion

Participants : Caroline de la Foye, Richard Kulpa, Franck Multon [ contact ] , Bruno Arnaldi.

We have developed a framework for animating human-like figures in real-time, based on captured motions. This work was carried-out in collaboration with the Lab. of Physiology and Biomechanics of Physical Exercise (LPBEM) from University Rennes 2. The first part of this work deals with the reconstruction of captured motion files. It is done offline with a software that imports motions in most usual formats like C3D (Vicon) or BVH (BioVision) and exports them in a morphology-independent file format which allows to replay the same motion on any avatar in a scene.

This format is based on a simplified skeleton which normalizes the global postural informations. This new formalism allows the motion to be adapted automatically to a new morphology in real-time (cf figure 1 ). This is done by taking kinematic constraints into account. This approach dramatically reduces the post production and allows the animators to handle a general motion library instead of one library per avatar. In order to facilitate the design of constraints, we have developed a xml-based language and a friendly user-interface. Hence, a user can add and edit constraints that are intrinsically linked to the motion, such as ensuring foot-contact with the ground, reaching targets for grasping motions...

Figure 1. Six characters with different morphologies replaying the same motion that is also adapted in real time to the evolution of the ground

The second part of the framework provides an animation library which blends several kinematic parametrized models and adapts them to the environment and the avatar's morphology. The library proposed motion synchronization, blending and adaptation to the skeleton and to constraints. All those processes are performed in real-time in an environment that can change at any time, unpredictably. As the constraints are associated to time interval during which their weight evolves continuously, the system can solve them at each time without requiring the knowledge of all the sequence. An inverse kinematic and kinetic solver was developed, based on the morphological-independent representation of posture introduced in  [24] . Using inverse kinetics enables to impose a position to the character's center of mass in order to deal with balance or dynamics (limited to the center of mass mechanical system).

This library has been used in several applications, for example in a virtual museum or a presentation for imagina 2002. It has been improved in the RIAM project "AVA-Motion", which ended in june 2004, to become a complete, "ready to use", library for industrial companies. It has also took part of the RIAM project "Semocap" (which will end in december 2005) that involves our partner: LPBEM, University Rennes 2. It currently runs on Windows and Linux with different viewers and it has been also integrated in two different software architectures: AVA from the Daesign company and OpenMASK, our own platform. It has been presented in SIGGRAPH 2005 exhibition at the INRIA's booth.


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