objective-c – Cocos2D Bezier曲线围绕物体,如同重力一样

在数学上,我如何找出贝塞尔曲线(1,2和结束)的三个点,并根据其距离给出一个重量(更远的=较小的拉力).我已经将距离映射到一个变量中.

想想一下在月球上弹弓的宇宙飞船.

码：

ccBezierConfig bezier;
bezier.controlPoint_1 = ccp(projectile.position.x + 10,projectile.position.y + 20);
bezier.controlPoint_2 = ccp(projectile.position.x + 20,projectile.position.y + 40);
bezier.endPosition = ccp(projectile.position.x + 30,projectile.position.y+60);
id bezierAction = [CCBezierTo actionWithDuration:1 bezier:bezier];
[projectile stopAllActions];
[projectile runAction: bezierAction];