Figure 1: Several steps of cable positioning on a cardoor. This quasi-dynamic simulation runs at real-time. AbstractIn this work, we propose interactive and physically based animation of one-dimensional deformable models using geometrically exact energy formulation. The proposed mechanical model has a high level of accuracy: it is based on continuous spline support and continuum mechanics media equations. We also detail a new efficient solving scheme, that can automatically switch between dynamic and static during simulation. With this scheme, we want to raise inconsistencies that could show up when human user is interacting with a physical simulation. We finally present a practical example in which the proposed model provides high-quality interaction.

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International audienceModels with impact or dry friction, yielding discontinuous velocities or accelerations, have motivated research for appropriate numerical methods in the community of non-smooth dynamics. In this work, we apply such methods on the grand piano action. This multibody system has two properties of interest in terms of modelling and simulation: it is extremely sensitive to small misadjustements, and its functioning strongly relies on dry friction and stick-slip transitions—known to be crucial for the touch of the pianist. Using numerical methods of non-smooth contact dynamics, the non-smooth character of dry friction was conserved, in contrast to classical approaches based on regularization which additionally impose the somewhat arbitrary choice of a regularizing parameter. The use of such numerical method resulted in computations about a few hundred times faster than those reported in recent literature. For the first time, the presented predictions of the piano action's simulations are forces (in particular, the reaction force of the key on the pianist's finger), instead of displacements which filter out most of the dynamical subtleties of the mechanism. The comparisons between measured and simulated forces in response to a given motion are successful, which constitutes an excellent validation of the model, from the dynamical and the haptic points of view. Altogether, numerical methods for non-smooth contact dynamics applied to a non-smooth model of the piano action proved to be both accurate and efficient, opening doors to industrial and haptic applications of sensitive multibody systems for which dry friction is essential.

Simulation-based videos

• Simulations of a keystroke:
  
  
  
  
• Comparisons between simulations and experiments:
  
  
  
  

• High-speed captures of the piano key mechanism (Left: piano keystroke. Right: forte keystroke.) [A. Thorin and X. Boutillon, LMS@École polytechnique / CEA LIST]
  
  
  
  
• Explanations on how the mechanism works [A. Thorin based on O. Remez's drawing]
  
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In the present paper, we introduce a new control architecture aimed at driving virtual humans in interaction with virtual environments, by motion capture. It brings decoupling of functionalities, and also of stability thanks to passivity.We show projections can break passivity, and thus must be used carefully.Our control scheme enables task space and internal control, contact, and joint limits management. Thanks to passivity, it can be easily extended.Besides, we introduce a new tool as for manikin's control, which makes it able to build passive projections, so as to guide the virtual manikin when sharp movements are needed.