A facial composite editor for blendshape characters

In this paper we present an interactive editing system that allows digital modelers to rapidly create new blendshape face models for incidental or background characters, starting from a small number of given face models. The obvious approach of generating linear combinations of the given models is limited in that it does not explore the combinatorial variety in the given source models. Instead, we take an approach similar to the "facial composite" systems used in forensics, in which face features (eyes, nose, mouth, etc.) from different individuals are assembled to create a composite likeness. A literal implementation of the facial composite idea does not produce realistic faces however, since choosing features from faces of different sizes can result in both unrealistic discontinuities and position relationship violations (a selected mouth might be at a higher position that the bottom of the nose selected from a different character). To handle this, we adopt a gradient-domain assembly and blending of the individual features, and produce the final face by integrating the resulting Poisson equation. This method guarantees that the result is smooth and that position relationships from the source characters are preserved. Additional blendshape expression targets are generated by the same approach, using the same gradient blending used to produce the neutral face. The resulting system is simple, operates at interactive rates, and has already proven itself in production.