Please see my comment to the question. As your difficulties with formulation of the problem and finding relevant information clearly demonstrate that you pretty poorly understand the essence of the problem, and it looks like the only prerequisites you have is the desire to have a "cool feature" (or something like that), your problems of getting such features working would be unmeasurably more difficult. For further steps, start here:
http://docs.opencv.org/trunk/modules/contrib/doc/facerec[
^].
—SA