可同时绘制多条贝塞尔曲线和B样条曲线 鼠标增加控制点，可显示或隐藏控制点 拖动控制点可改变曲线 -Can also draw a number of Bezier curves and B-spline curve Point the mouse to increase control, can display or hide the control point Drag the control point can change the curve