tutorial 4
T4  Inverse Kinematics and Kinetics for Virtual Humanoids

Date: Tuesday, September 4th, Time: 14:00 - 17:30, Location: Lecture Room 209

Organizers:  Ronan Boulic (EPFL)
Richard Kulpa (M2S)
Speakers:  Ronan Boulic (EPFL)
Richard Kulpa (M2S)


The present tutorial deals with the use of inverse kinematics and kinetics for postural adaptations of virtual humanoids to different kind of constraints. It proposes an overview of the problematic of this thematic and then of the existing techniques. The core of the tutorial describes two main approaches: the prioritized inverse kinematics for accurate and realistic adaptation and a CCD-like algorithm based on groups for fast and realistic adaptation of hundreds of characters in real-time. Consequently, this tutorial can be accessible for beginners in order to have an overview of this thematic and its advantages/drawbacks (illustrated by numerous figures/animations) and for advanced users who want to find concrete solutions depending on the complexity of their problem.


Extended Summary

The tutorial is organized in three main parts. First, we describe the motivations and an overview of existing IK techniques with their advantages and drawbacks.

The second part provides an in-depth presentation of the Prioritized Inverse Kinematics as it allows the application level to sort the various constraints according to their importance. Prioritizing the constraints also produces a convergence behavior with intermediate believable postures as the most important constraints are enforced first, and generally very quickly. This is in contrast with the traditional approach with weighted constraints where none is absolutely guaranteed when they conflict with each other. This can lead to local minima or unplausible intermediate/final postures.

The third part provides an in-depth presentation of the CCD-like algorithms and more precisely the combination of a CCD algorithm applied on body groups with analytical methods. This hybrid algorithm allows to adapt very quickly the posture to many constraints that can be weighted or prioritized. An extension of this algorithm is also detailled to show how the center of mass of the character can be preserved. At last, this part provides a complete kinematics and kinetics inverse solver for interactive applications of many characters.

Speakers' Background

Ronan Boulic is a Senior Researcher, Lecturer and PhD Advisor at the Swiss Federal Institute of Technology, Lausanne (EPFL). He is working in the Virtual Reality Lab and his research interests include 3D interaction, motion capture, movement modeling, and postural control for virtual humans and robots. He received the PhD degree in Computer Science in 1986 from the University of Rennes, France, at the INRIA-IRISA research institute. He received the habilitation degree from the University of Grenoble, France, in march 1995. Ronan Boulic is co-author of 102 research papers among which 27 appeared in international peer-reviewed journals. He has been chairman of the Eurographics Workshop on Computer Animation and Simulation 1996, program committee member of Eurographics, ACM SCA, Computer Animation and Computer Graphics International, and he was part of the organization committee of Eurographics'03 and '05. He was Paper co-chair of the Eurographics/SIGGRAPH Symposium on Computer Animation 2004 in Grenoble. He is currently short paper co-chair of ACM VRST 2007.

Richard Kulpa is an Assistant Professor at the M2S laboratory of the University of Rennes 2, France. He is also an external collaborator of the Bunraku team of the IRISA-INRIA Rennes research institute. His research interests include biomechanics, realistic humanoids animation and virtual reality. He worked since 1996 as a research engineer in the SIAMES team (now Bunraku) where he worked on behavioral animations of characters in informed environments in collaboration with French multimedia companies. Since 2000, in parallel to these previous works, he has integrated the LPBEM laboratory where he worked on biomechanics and the understanding of the human movement. At last, he received his PhD in 2005 for a work that combines biomechanics and iterative inverse kinematics and kinetics solver in order to have realistic animation of hundreds of characters in real-time. He received a price at Eurographics 2005 concerning this work. By the way, he co-created the MKM animation engine that incorporates all these works.

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Last update : 12.05.2011

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