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张量积Bézier曲面降多阶逼近的方法

New Approach to Approximate Multi-degree Reduction of Tensor Product Bézier Surfaces

  • 摘要: 提出根据原张量积Bézier曲面Pn,m(u,v)与降多阶张量积Bézier曲面Qn1,m1(u,v)(n1n-1,m1m-1)在最小二乘范数下的距离函数在单位正方形0,1×0,1上取最小值,得到张量积Bézier曲面降多阶逼近的方法,以及用矩阵表示的降多阶张量积Bézier曲面Qn1,m1(u,v)的控制顶点\left\q_i j\right\_i=0, j^n 1, m_1=0的显式表示式. 在降多阶过程中,分别考虑了带角点高阶插值条件和不带角点插值条件的情形. 数值例子显示,采用文中方法所得降多阶曲面比已有的方法所得降多阶曲面对原曲面的逼近效果更好.

     

    Abstract: An approach is presented through minimizing the distance function between Pn,m(u,v) and Qn1,m1(u,v)(n1n-1,m1m-1) over unit square [0,1]×[0,1] in the sense of least squares normal (L2),which gives the explicit representation of control points\left\q_i j\right\_i=0, j^n 1, m_1=0 of the reduced multi-degree tensor product Bézier surface Qn1,m1(u,v).During the multi-degree reduction process,we also consider two cases,one has the constraint of high-order interpolations over corners and another without any constraint.Examples show that the proposed approach has better approximation of the reduced surfaces than that of current methods.

     

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