在SpriteKit中使用touchesMoved旋转奖品轮 [英] Spinning a prize wheel with touchesMoved in SpriteKit

问题描述

是否可以使用applyAngularImpulse而不是以指数方式提高车轮的速度？

理想情况下，我想让车轮跟随我的手指，但设置 node.zRotation + = atan2f（y2-y1，x2-x1）旋转我的轮子失去控制。这就是我所确定的，但感觉非常不稳定：

is it possible to use applyAngularImpulse but not exponentially increase the speed of the wheel?
Ideally I'd like to have the wheel follow my finger, but setting node.zRotation += atan2f(y2-y1, x2-x1) spins my wheel out of control. here's what i settled on, but it feels pretty wonky:

- (void) touchesMoved:(NSSet *)touches withEvent:(UIEvent *)event {

  UITouch *touch = [touches anyObject];
  SKNode *node = [self nodeAtPoint:location];

  CGPoint positionInScene = [touch locationInNode:self];
  CGPoint previousPosition = [touch previousLocationInNode:self];

  [node.physicsBody applyAngularImpulse:(previousPosition.x - positionInScene.x) * 0.1];
  node.physicsBody.angularDamping = 1;
}

场景： https://dl.dropboxusercontent.com/s/gexfburjm1coude/Screen ％20Shot％202014-10-21％20at％2010.30.31％20 PM.png？dl = 0

推荐答案

应用你的冲动后：

[node.physicsBody applyAngularImpulse:theImpulse];

只需将角速度钳制到最大速度，其最大速度取决于您想要允许车轮的速度旋转：

Simply clamp the angular velocity to a maximum speed whose value depends on how fast you want to allow the wheel to spin:

const CGFloat maxAngularVelocity = 2.5;
node.physicsBody.angularVelocity = MIN(node.physicsBody.angularVelocity, maxAngularVelocity);

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