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点到NURBS曲线最近距离的快速计算方法

Fast Approach for Computing the Minimum Distance between a Point and a NURBS Curve

  • 摘要: 点/曲线的最近距离在几何造型中有着较广泛的应用,特别是在实时性要求很高的应用中,最近距离计算的效率也相应地面临越来越高的要求.为此,提出混合基于控制多边形的细分位置快速估算、分类剔除,以及渐进求根法等技术的点到NURBS曲线最近距离的快速计算方法.首先将平方距离函数转化为Bézier形式;然后根据对应的控制多边形信息来快速估算细分位置,并根据分类技术进行剔除;最后使用高阶收敛的渐进求根方法计算出相应的最近点.该方法只需要一次Bézier形式的转换,具有比圆裁剪更好的裁剪效果.数值实例结果表明,与已有的圆裁剪等方法相比,混合的快速计算方法可以具有更高的裁剪效率和计算效率.

     

    Abstract: Point projection problem of NURBS curves has a wide application in geometric modeling system.A fast approach is presented for computing the minimum distance between a point and a NURBS curve.It combines a control-polygon-based method for searching the subdivision position,the classification based clipping method with progressive root-finding technique.It firstly translates the square distance function into Bézier form; and then,estimates the subdivision positions by using the control polygon,and does the clippings based on classification; finally it computes the minimum distance by using progressive root-finding technique.It can achieve a better clipping effect than the circle-clipping methods.Numerical examples show that the new method can achieve better clipping efficiency and better computational efficiency than those of circle clipping method and other prevailing methods.

     

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