S曲线

Besides the handles, every control point also has points that define the feather betweenthe current point and the next point on the spline.Each feather point is stored in UW space,where U means position across spline segment, and W (weight) means distance between main spline and feather points.

这允许以几乎任何方式使主样条变形，并且羽化将自动更新以反映该变化。

参考