The accuracy of Generic mesh conformation; the future of facial morphological analysis

3D analysis of the face is required for the assessment of changes following surgery, to monitor the progress of pathological conditions and for the evaluation of facial growth. Sophisticated methods have been applied for the evaluation of facial morphology, the most common one is the dense surface correspondence. The method depends on the application of a mathematical facial mask known as the generic facial mesh for the evaluation of the characteristics of facial morphology. This study was carried out to evaluate the accuracy of the conformation of generic mesh to the underlying facial morphology. The study was conducted on 10 non-patient volunteers. Thirty-four 2mm diameter self-adhesive non-reflective markers were placed on each face. These were readily identifiable on the captured 3D facial image which was captured using Di3D stereophotogrammetry. The markers helped in minimizing the digitization errors during the conformation process. For each case the face was captured 6 times, at rest and at the maximum movements of 4 facial expressions. 3D facial image of each facial expression was analysed. Euclidean distances between the 19 corresponding landmarks on the conformed mesh and on the original 3D facial model provided a measure of the accuracy of the conformation process. For all facial expressions and all corresponding landmarks these distances were between 0.7 and 1.7 mm. The absolute mean distances ranged from 0.73mm to 1.74mm. The mean absolute error of the conformation process was 1.13mm±0.26mm.The conformation of the generic facial mesh proved to be accurate enough for the analysis of the captured 3D facial images.