用鼠标拖动输入的点做为控制顶点，生成一条B-样条曲线，显示控制顶点和多边形。用鼠标Pick曲线上任意一点，移动鼠标到新位置改变曲线形状。-Use the mouse to drag the input points as control points to generate a B-spline curve, display control vertex and polygon. Pick curve with the mouse on any point, move the mouse to a new location to change the curve shape.