Three-dimensional face shape analysis of French adults, and its application to the design of protective equipment.

The study's aim was to identify female and male face shape variability in order to establish typical profiles for the design of masks. A specific data acquisition photogrammetric station was used for this purpose. A preliminary survey using anthropometric techniques was conducted on 301 females and 208 males, randomly selected from the French military population, in order to constitute two samples of 30 males and 30 females for the stereometric survey. For each subject, the stereorestitution of face photos was made on three sets of data: (1) 37 anatomical landmarks previously identified by a black point marked on the face; (2) 7 anatomical arcs, also drawn with a black pencil; and (3) 1500-2000 points distributed on horizontal cross-sections at different vertical levels. The analysis only concerned the global face shape, and excluded the central area (eyes, nose and mouth). A common origin and reference axis system was defined. All the three-dimensional (3D) produced data was processed using computer-aided design software, after some adaptations. Subjects were selected iteratively for five levels of cross-section and three anatomical arcs so as to characterize least variation amplitudes, subject by subject. Five groups were identified. All cross-sections were verified to check the validity of the preceding step. By this method, each group was defined by a mean profile form and by the amplitude of this form for each point of the profile. Males and females were present in each group, and for each group, a greater variability was noted at the lower part of the face. This variability can be explained as the result of morphological and functional phenomena. These results can be applied to the design of new protective equipment for the fore-face indeed they were used for the design of a new mask for the French military.