功能：

四点插值细分曲线

操作说明：

1．点击鼠标左键在界面上按顺序画出控制多边形的顶点

2．点击鼠标右键确认输入完毕

3．点击鼠标左键进行一次细分

-Features: four-point interpolatory subdivision curve Instructions: 1. Click the left mouse button in the interface in order to draw the control polygon vertices 2. Click the right mouse button confirm the input end 3. Click the left mouse button once sub-