问题描述
我想使用 applyImpulse 方法在基于 PhysicsBody 旋转的方向上移动一个physicsBody.
I want to move a physicsBody with the applyImpulse method in a direction based on the physicsBody rotation.
例如，physicsBody 是一个正方形，我称之为移动"，它会施加一个脉冲使其垂直向上移动.然后我调用一个方法将physicsBody 向右旋转45 度.如果我再次调用move"方法，physicsBody 将沿对角线向右和向上移动.
Foe example, the physicsBody is a square in shape, I call a "move" which will apply an impulse to make it move up vertically. I then call a method to rotate the physicsBody 45 degrees right. If I call the "move" method again, the physicsBody will move diagonally right and up.
推荐答案
我建议你遵循 Sprite Kit 的坐标和旋转约定.具体来说，您的精灵图像应该正对零度(默认值)，正值是逆时针旋转.也就是说，这是在精灵面对的方向上施加脉冲的一种方法:
I suggest that you follow Sprite Kit’s coordinate and rotation conventions. Specifically, your sprite image should be facing right at zero degrees (the default value), and a positive value is a counter-clockwise rotation. That said, here's one way to apply an impulse in the direction a sprite is facing:
// Specify the force to apply to the SKPhysicsBody
CGFloat r = 5;
// Create a vector in the direction the sprite is facing
CGFloat dx = r * cos (sprite.zRotation);
CGFloat dy = r * sin (sprite.zRotation);
// Apply impulse to physics body
[sprite.physicsBody applyImpulse:CGVectorMake(dx,dy)];
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