如何获得速度的角度来旋转子弹？

Question

我有这样的：

CGPoint vel = hudLayer.rightJoystick.velocity; 

      CCBullet* sp = [CCBullet spriteWithFile:@"green.png"]; 
      sp.position = player.position; 
      [self addChild:sp z:-10]; 

      vel = ccpMult(ccpNormalize(vel), 300); 
sp.rotation = //how to get the rotation out of the velocity? 

任何帮助吗？

Answer 1

float angle = atan2f(vel.y, vel.x);