“…As a result, the key to successfully applying the ICP algorithm for 3D free form shape registration lies in eliminating the correspondences with relatively lower qualities. For this purpose, the following techniques have been proposed: † Increase the dimensionality of points from 3D [3,4] to higher dimensions by incorporating other geometric or optical features, such as normal vectors [12], invariants [44], curvature [55], laser reflectance strength value [35], and colours [22]; † Sample points uniformly [51], in normal space [42], or based on covariance matrix [14]; † Establish correspondences from matching points to matching curves [48,53] to matching 2D images [20,23,54], from matching local structural features to examining motion consistency [28,31,41] to combining both [27]; † Consider the reliability of point correspondences as a function of the cosine of the including angle between vertex normals and their viewing directions [51]; † Eliminate false matches through removing boundary points [42,51], checking interpoint distance consistency [11] or orientation consistency [38,57], examining motion consistency [29][30][31]41], or examining both the motion and structural consistency [28,27]; † Estimate motion parameters from using least squares to using weighted least squares [51], genetic algorithm [45], M-estimator [35] or simulated annealing [33], or from the Euclidean space to the frequency space [32].…”