1. A method for estimating a 3D vector angle from a 2D face image, comprising the steps of: creating a feature vector template including a feature vector model of a plurality of different rotation angles; detecting corners of the eyes and corners of the mouth in a face image to be processed, and defining the corners of the eyes and the corners of the mouth as vertices of a quadrilateral, respectively; defining a sharp point displaced in an orthogonal direction relative to the quadrilateral plane, and converting the vertices into 3D coordinates, wherein the sharp point and the vertices of the quadrilateral form a quadrangular pyramid; computing the four 3-D vectors, each 3-D vector extending from the sharp point to a respective one of the four vertices, wherein the coordinates of said 3-D vectors are 3D coordinates, and wherein said 3-D vectors are computed to obtain a vector set, and matching the vector set with the feature vector model to obtain an angle which has the shortest distance between a feature vector model and the vector set of said four 3-D vectors, and defining the angle value as a rotation angle of the input face image.