利用曲面网格的边界曲线直接定义3D曲面，既能保证曲面的光滑过渡，即C1连续，又可避免通过确定扭矢来达到控制曲面的复杂计算。
The 3D surface can be defined directly by the boundary curve of the patch surface. The surface will be C1 continuous if the boundary curves connecting each two patches are C1 continuous.
二种最普遍使用正颚手术方法来改善下颚骨前突症的方法是双侧矢向面骨切开术及垂直下颚枝骨切开术。
The two most commonly used surgical techniques to setback a prognathic mandible include the bilateral sagittal split osteotomy and the vertical ramus osteotomy.
通过计算环的最大坐标值点处相邻两条边的切矢的叉积来判断环的方向。
The loop direction is judged through the vector product of the adjacent two edges on the vertex with maximum coordinate value.
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