I have tried face recognition using OpenCV using the documentation provided on their wiki. Its working fine and it can detect multiple faces. However there is no data provided on the site regarding 3D object detection or head tracking. The links to the code and the wiki are provided below :
While the wiki does provide sufficient information about face detection, as you might have found, 3D face recognition methods are not provided.
I wanted to know about projects related to 3D face recognition and tracking so that I can see the source code and try to make a project doing the same.