Flynn Cormac, Stavness Ian, Lloyd John, Fels Sidney
a Department of Electrical and Computer Engineering , University of British Columbia , 2332 Main Mall, Vancouver , BC , Canada V6T 1Z4.
Comput Methods Biomech Biomed Engin. 2015;18(6):571-82. doi: 10.1080/10255842.2013.820720. Epub 2013 Aug 6.
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.
人脸计算机模型有潜力成为手术模拟和动画开发应用中的强大工具。虽然现有模型能准确呈现面部的各种解剖特征，但皮肤和软组织的呈现非常简化。本文提出一种人脸计算机模型，其中皮肤由正交各向异性超弹性本构模型表示。模型中还体现了皮肤固有的体内张力。通过激活适当的口面部和颌部肌肉来模拟几种面部表情，对该模型进行了测试。之前的实验计算了患者面部椭圆形伤口长轴方向在张大嘴巴和张嘴微笑（均为30°）时的变化。将这些结果与在人脸模型中计算得到的张大嘴巴（18°）和张嘴微笑（25°）时皮肤最大主应力方向的平均变化进行了比较。将四种面部表情下脸部标志点的位移与文献中的实验测量结果进行了比较。模型中嘴角在每种面部表情下的位移最大（约11 - 14毫米）。模拟的标志点位移在测量位移的标准差范围内。增加皮肤刚度和皮肤张力通常会导致面部表情时标志点位移减小。
