1. A computer-implemented process for generating a face recognition training database for each person detected as being located in an environment, comprising: using a computer to perform the following process actions: (a) inputting a sequence of contemporaneously-captured frame pairs, each frame pair comprising a frame output from a color video camera and a frame output from a depth video camera; (b) using a face detection method and the color video camera frames to detect potential persons in a environment; (c) using a motion detection method and the depth video camera frames to detect potential persons in the environment; (d) using detection results generated via the face detection method and motion detection method to determine the location of one or more persons in the environment, said detection results generated via the face detection method comprising for each person detected, a facial characterization of the portion of a color video camera frame depicting the person's face; (e) for each person detected solely via the motion detection method, identifying the corresponding location of that person in the contemporaneously-captured frame of the color video camera, generating said facial characterization of the portion of the color video camera frame depicting that person's face; (f) for each person detected in the environment, assigning each facial characterization generated for that person to an unknown person identifier established for the person, storing each of said facial characterizations in a memory associated with the computer, attempting to ascertain the identity of the person, and whenever the identity of the person is ascertained, re-assigning each facial characterization assigned to the unknown person identifier established for the person to a face recognition training database established for that person.