三维颅面软组织因受重力影响在躺卧与直立两种姿态下的差异较大,为将躺卧姿态下获取的三维颅面模型矫正为直立姿态下的三维模型,本文提出了一种基于测地线的躺卧三维颅面模型的直立矫正方法.首先利用测地距离的内蕴几何不变性,建立两种姿态下面部特征点的点对应;然后,利用主成分分析建立颅面特征点运动模型;最后,对待矫正的躺卧颅面模型,根据颅面特征点运动模型确定特征点的运动,根据特征点的运动确定躺卧颅面模型到直立颅面模型的变形.所提方法将与直立姿态人脸模型间的平均误差从矫正前的10-2数量级下降到矫正后的10-4数量级.本文利用测地距离的内蕴几何不变性,解决了两种姿态下面部特征点对应的难题;所建立的颅面特征点运动模型,能够较好地表示颅面在两种姿态下发生的形变,从而能够实现有效地模型矫正.%The three-dimensional craniofacial soft tissue shapes in the upright and lying postures are different due to the gravity.In order to rectify the three-dimensional craniofacial model from the lying posture to one from the upright posture,a rectification technique of three-dimensional craniofacial models based on geodesic was proposed.Firstly,the correspondences of the craniofacial feature points under two postures were established by using the intrinsic geometric invariance of geodesic distance;Secondly,a statistical model of the feature point motion from lying to upright posture was established by using principal component analysis;Finally,for a craniofacial model in lying posture,the motion of the feature points was determined by the statistical model,and the deformation of the craniofacial model from lying posture to one from upright posture was determined according to the motion of the feature points.The mean error was decreased from 10-2orders of magnitude before correction to 10-4 orders of magnitude after correction.The problem of point correspondence between two postures was well solved by using the intrinsic geometric invariance of geodesic distance.The established feature point motion model can well represent the deformation of the craniofacial model from lying posture to one from upright posture,and thus can achieve effective model correction.
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