text: The process begins with a computer constructing a 3-D model of the face and all 44 major muscles must move like a human face. These movements are called action units. Dr. Paul Eckman, creator of FACS, classified the six basic emotions of facial expressions; happiness, sadness, surprise, anger, disgust, and fear, and implied them to facial muscles. The software can even track mixed emotions. For example, the Mona Lisa as she has four different emotions in her picture.