曲线的定义有四个点：起始点、终止点（也称锚点）以及两个相互分离的中间点。滑动两个中间点，贝塞尔曲线的形状会发生变化-There are four points to define the curve: the starting point, end point (also known as the anchor) and an intermediate point between the two separated each other. Slide the two intermediate