Bar‐net driven skinning for character animation

In this paper we present a physically motivated technique for the deformation of animated characters, called the bar‐net driven skinning. We use a bar‐network (bar‐net) as a deforming mechanism. This technique can be used similarly to a conventional skinning tool, but can also make a skin surface behave in a physically plausible manner due to the inherent physical properties of the network. A bar‐net is a structure commonly used in structural engineering. Its shape depends on the structural and material properties and the forces acting upon it. Computing the rest shape of an arbitrary bar‐net is a time‐consuming non‐linear problem. In order to speed up the computation and also for such a bar‐net to be used intuitively to help computer animation, we have defined a set of properties that a desirable bar‐net should satisfy. This allows a bar‐net shape finding problem to be solved using linear equations. We adopt a two‐layer structure for the representation of a skin surface, including a coarse mesh and a fine mesh. To deform a skin surface, we couple a bar‐net to its coarse mesh, which in turn deforms the fine mesh when the coupled bar‐net is deformed. The fine surface mesh can be of different forms, including Nurbs, subdivision surfaces and polygons. Copyright © 2007 John Wiley & Sons, Ltd.