Three-dimensional facial capture using a custom-built photogrammetry setup:Design, performance, and cost

Introduction: Although stereophotogrammetry is increasingly popular for 3-dimensional face scanning, commercial solutions remain quite expensive, limiting its accessibility. We propose a more affordable, custom-built photogrammetry setup (Stereo-Face 3D, SF3D) and evaluate its variability within and between systems. Methods: Twenty-nine subjects and a mannequin head were imaged 3 times using SF3D and a commercially available system. An anthropometric mask was mapped viscoelastically onto the reconstructed meshes using MeshMonk (https://github.com/TheWebMonks/meshmonk). Within systems, shape variability was determined by calculating the root-mean-square error (RMSE) of the Procrustes distance between each of the subject's 3 scans and the subject's ground truth (calculated by averaging the mappings after a nonscaled generalized Procrustes superimposition). Intersystem variability was determined by similarly comparing the ground truth mappings of both systems. Two-factor Procrustes analysis of variance was used to partition the intersystem shape variability to understand the source of the discrepancies between the facial shapes acquired by both systems. Results: The RMSEs of the within-system shape variability for 3dMDFace and SF3D were 0.52 +/- 0.07 mm and 0.44 +/- 0.16 mm, respectively. The corresponding values for the mannequin head were 0.42 +/- 0.02 mm and 0.29 +/- 0.03 mm, respectively. The between-systems RMSE was 1.6 +/- 0.34 mm for the study group and 1.38 mm for the mannequin head. A 2-factor analysis indicated that variability attributable to the system was expressed mainly at the upper eyelids, nasal tip and alae, and chin areas. Conclusions: The variability values of the custom-built setup presented here were competitive to a state-of-the-art commercial system at a more affordable level of investment.