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几何迭代逼近算法的权重选取方法

Weight Selection of Geometric Iterative Method for Curve and Surface Approximation

  • 摘要: 几何迭代法通过构造数据点到逼近曲线(曲面)上对应点的误差向量迭代修正曲线(曲面)实现对数据点的逼近.针对几何迭代法中影响收敛性和收敛速率的误差向量的权重选取问题, 以局部逼近几何迭代法为例, 提出渐进迭代过程中权重的3类选取方法. 首先分析满足算法收敛条件的权重取值范围, 然后根据理论最快下降速率、矩阵特征值的范数不等式和自由变形(free-form deformation, FFD)方法提出了不同的权重计算策略. 此外, 为提升计算效率, 提出利用初始化配置矩阵固定权重的方法. 最后, 通过含不同数量数据点和控制点的曲线及曲面逼近实例, 评估权重策略的性能. 实验结果表明, 在相同迭代次数下, 曲线逼近中理论最快下降速率和L1范数/L范数下的权重平均误差更小, 曲面逼近中FFD方法下的权重平均误差更小, 均表现出更快的收敛速率; 在相同误差下, 固定权重耗时更少, 计算效率显著提高.

     

    Abstract: The geometric iterative method approximates the target curve (surface) by minimizing the distance between given data points and corresponding points on the approximate curve (surface). To address the issue of selecting weights for error vectors that affect the convergence and convergence rate in geometric iterative methods, this study takes the local approximation geometric iterative method as an example and proposes three types of weight selection methods for the progressive iterative process. Firstly, the range of weight values is analyzed to satisfy the convergence conditions of the algorithm. Then, different weighting methods are proposed based on the theoretical fastest rate, norm inequality of matrix eigenvalues, and the FFD(free-form deformation) method. To improve computational efficiency, a method of fixing weights using the initialized configuration matrix is also proposed. Finally, the performance of the weighting methods is evaluated through curve and surface approximation examples with different numbers of data points and control points. The experimental results indicate that, under the same number of iterations, the theoretical fastest rate and  norm or  norm weighting methods achieve smaller average errors in curve approximation, while the FFD-based method demonstrates smaller average errors in surface approximation, both exhibiting faster convergence rates. Under the same error threshold, the fixed weighting method takes less time, significantly improving the computational efficiency.

     

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