说明：  运用计算机图形学的知识，采用4阶B样条基函数，节点向量取为[0,0,0,0,1/4,2/4,3/4,1,1,1,1] 先绘制控制多边形，再用分段直线段绘制B样条曲线
(Using the knowledge of computer graphics, the 4 order B spline basis function is used, and the node vector is taken as [0,0,0,0,1/4,2/4,3/4,1,1,1,1]. First, draw the control polygon and draw the B spline curve by piecewise straight line segments.)