A Muscle Model for Enhanced Character Skinning

Abstract

This paper presents a novel method for deforming the skin of 3D characters in real-time using an underlying set of muscles. We use a geometric model based on parametric curves to generate the various shapes of the muscles. Our new model includes tension under isometric and isotonic contractions, a volume preservation approximation as well as a visually accurate sliding movement of the skin over the muscles. The deformation of the skin is done in two steps: first, a skeleton subspace deformation is computed due to the bones movement; then, vertices displacements are added due to the deformation of the underlying muscles. We have tested our algorithm with a GPU implementation. The basis of the parametric primitives that serve for the muscle shape definition is stored in a cache. For a given frame, the shape of each muscle as well as its associated skin displacement are defined by only the splines control points and the muscle’s new length. The data structure to be sent to the GPU is thus small, avoiding the data transfer bottleneck between the CPU and the GPU. Our technique is suitable for applications where accurate skin deformation is desired as well as video games or virtual environments where fast computation is necessary.