title: A finite element model of the face including an orthotropic skin model under in vivo tension.
abstract: Computer models of the human face have the potential to be used as powerful tools in surgery simulation and animation development applications. While existing models accurately represent various anatomical features of the face, the representation of the skin and soft tissues is very simplified. A computer model of the face is proposed in which the skin is represented by an orthotropic hyperelastic constitutive model. The in vivo tension inherent in skin is also represented in the model. The model was tested by simulating several facial expressions by activating appropriate orofacial and jaw muscles. Previous experiments calculated the change in orientation of the long axis of elliptical wounds on patients' faces for wide opening of the mouth and an open-mouth smile (both 30(o)). These results were compared with the average change of maximum principal stress direction in the skin calculated in the face model for wide opening of the mouth (18(o)) and an open-mouth smile (25(o)). The displacements of landmarks on the face for four facial expressions were compared with experimental measurements in the literature. The corner of the mouth in the model experienced the largest displacement for each facial expression (∼11-14 mm). The simulated landmark displacements were within a standard deviation of the measured displacements. Increasing the skin stiffness and skin tension generally resulted in a reduction in landmark displacements upon facial expression.
authors.affiliation: a Department of Electrical and Computer Engineering , University of British Columbia , 2332 Main Mall, Vancouver , BC , Canada V6T 1Z4.
authors.forename: Cormac
authors.initials: C
authors.lastname: Flynn
authors.forename: Ian
authors.initials: I
authors.lastname: Stavness
authors.forename: John
authors.initials: J
authors.lastname: Lloyd
authors.forename: Sidney
authors.initials: S
authors.lastname: Fels
mesh_terms: D000328:Adult; D001696:Biomechanical Phenomena; D003198:Computer Simulation; D004548:Elasticity; D005145:Face / Q000502:physiology*; D020342:Finite Element Analysis; D006801:Humans; D007091:Image Processing, Computer-Assisted; D008297:Male; D008954:Models, Biological; D009068:Movement; D010363:Pattern Recognition, Automated; D012867:Skin; D013314:Stress, Mechanical
keywords: anisotropy; constitutive model; expressions; face model; in vivo tension