should construct a face detector according to the given file.
After linking a model instance and a detecor in the main file, the next step is passing the observation for each frame and do the optimization in Optimizer::optimize.
How to modify the face detector:
For a detector object, _jointPointMap is mapping from a joint's name to the serial number of its tracking point. More specifically, in face_detector.cpp,
_jointPointMap["noseRt_tz"] = 31;
should map the noseRt_tz joint to the 31st point found by dlib.
In detecrtor.cpp, Detector::updateModels(int index) is updating a corresponding instance by the tracking points.