On extracting the wire curves from multiple face models for facial animation

Abstract

Wire curve (SIGGRAPH 98 Conference Proceedings, 1998, p. 299) is a simple, intuitive interface to local deformation of complex geometric objects such as human face models. In this paper, we provide a formulation to extract wire curves and deformation parameters from a facial model based on the displacements of its vertices from those of the corresponding reference model. This extraction process is an inverse process of the wire deformation. With a mild assumption and interactive guide for setting the reference curves and their attributes, we show that the inverse process can be nicely formulated as an over-constrained system of linear equations that can be solved with a least-squares minimization technique. We apply the extraction process to multiple face models with different types of expressions to obtain their corresponding wire curves. For facial animation, we blend those extracted wire curves and deformation parameters to finally deform the reference face model. Our proposed scheme facilitates both local deformation and non-uniform blending by making use of the power of wire deformation. (C) 2004 Elsevier Ltd. All rights reserved.