在SpriteKit

Question

我正在制作一个简单的游戏，它有一根固定在屏幕中间的弹性绳索，还有一个连接到绳子另一端的球。通过在屏幕上移动手指，您可以移动球，并且可以将球向上拉到底部，从而将球向上扔。

到目前为止我的代码看起来像这样：

var ball = SKSpriteNode(imageNamed: "Ball")

override func didMove(to view: SKView) {
    var ropeSegments = [SKSpriteNode]()

    let ropeHolder = SKSpriteNode(imageNamed: "RopeHolder")
    ropeHolder.position = CGPoint(x: frame.midX, y: frame.midY)
    ropeSegments.append(ropeHolder)
    addChild(ropeHolder)

    ropeHolder.physicsBody = SKPhysicsBody(circleOfRadius: ropeHolder.size.width / 2)
    ropeHolder.physicsBody?.isDynamic = false

    for i in 0..<30 {
        let ropeSegment = SKSpriteNode(imageNamed: "RopeTexture")
        let offset = ropeSegment.size.height * CGFloat(i + 1)
        ropeSegment.position = CGPoint(x: ropeHolder.position.x, y: ropeHolder.position.y - offset)
        ropeSegments.append(ropeSegment)
        addChild(ropeSegment)

        ropeSegment.physicsBody = SKPhysicsBody(rectangleOf: ropeSegment.size)
    }

    for i in 1..<31 {
        let nodeA = ropeSegments[i - 1]
        let nodeB = ropeSegments[i]
        let joint = SKPhysicsJointPin.joint(withBodyA: nodeA.physicsBody!, bodyB: nodeB.physicsBody!, anchor: CGPoint(x: nodeA.frame.midX, y: nodeA.frame.midY))

        physicsWorld.add(joint)
    }

    ball.position = CGPoint(x: frame.midX, y: ropeSegments.last!.position.y - ball.size.height / 2)
    ball.physicsBody = SKPhysicsBody(circleOfRadius: ball.size.width / 2)
    addChild(ball)

    let joint = SKPhysicsJointPin.joint(withBodyA: ropeSegments.last!.physicsBody!, bodyB: ball.physicsBody!, anchor: CGPoint(x: ropeSegments.last!.frame.midX, y: ropeSegments.last!.frame.midY))
    physicsWorld.add(joint)

    let moveAction = SKAction.move(to: CGPoint(x: frame.midX - 100, y: frame.midY), duration: 0.5)
    ball.run(moveAction)
}

override func touchesMoved(_ touches: Set<UITouch>, with event: UIEvent?) {
    for touch in touches {
        let point = touch.location(in: self)
        ball.position = point
    }
}

绳索的表现非常类似于现实生活中的绳索，但它根本没有弹性。我能够尽可能多地拉球，但是绳子节点以非常缓慢的方式回到默认状态，所以不可能将球扔到身边。

我尝试使用SKPhysicsJointSpring代替SKPhysicsJointPin，但它的行为几乎相同。有什么建议吗？