It should be noted that the method for face tracking described in this chapter is a bare-bones approach that serves to highlight the various components utilized in most non-rigid face tracking algorithms. The numerous approaches to remedy some of the drawbacks of this method are beyond the scope of this book and require specialized mathematical tools that are not yet supported by OpenCV's
functionality. The relatively few commercial-grade face-tracking software packages available is testament to the difficulty of this problem in the general setting. Nonetheless, the simple approach described in this chapter can work remarkably well in constrained settings.