Question

我正在尝试设置一个围绕固定点旋转的SKShapeNode取决于用户的滑动手势。这样做我正在使用回答here.

的代码

当我将节点设置为矩形时 - 它工作正常，问题是当我尝试将节点设置为圆形时（因为我需要它）。我不知道为什么会发生这种情况，以及它与众不同之处。

这是有效的代码（SKShapeNode为矩形）：

override func didMove(to view: SKView) {
    let ball = SKShapeNode(rect: CGRect(x: 100, y: 100, width: 100, height: 100))
    ball.fillColor = SKColor.red
    ball.position = CGPoint(x: self.frame.size.width/2, y: self.frame.size.height/2)
    ball.name = "BALL"
    ball.physicsBody = SKPhysicsBody(circleOfRadius: 200)
    ball.physicsBody?.angularDamping = 0.25
    ball.physicsBody?.pinned = true
    ball.physicsBody?.affectedByGravity = false
    self.addChild(ball)

    let om = 5.0
    let er = 4.0
    let omer = atan2(om, er)
    print("om = \(om), er = \(er), atan2(omer) = \(omer)")


}


override func touchesBegan(_ touches: Set<UITouch>, with event: UIEvent?) {
    for touch in touches {
        let location = touch.location(in:self)
        let node = atPoint(location)
        if node.name == "BALL" {
            let dx = location.x - node.position.x
            let dy = location.y - node.position.y
            // Store angle and current time
            startingAngle = atan2(dy, dx)
            startingTime = touch.timestamp
            node.physicsBody?.angularVelocity = 0
        }
    }
}

override func touchesMoved(_ touches: Set<UITouch>, with event: UIEvent?) {
    for touch in touches{
        let location = touch.location(in:self)
        let node = atPoint(location)
        if node.name == "BALL" {
            let dx = location.x - node.position.x
            let dy = location.y - node.position.y

            let angle = atan2(dy, dx)
            // Calculate angular velocity; handle wrap at pi/-pi
            var deltaAngle = angle - startingAngle!
            if abs(deltaAngle) > CGFloat.pi {
                if (deltaAngle > 0) {
                    deltaAngle = deltaAngle - CGFloat.pi * 2
                }
                else {
                    deltaAngle = deltaAngle + CGFloat.pi * 2
                }
            }
            let dt = CGFloat(touch.timestamp - startingTime!)
            let velocity = deltaAngle / dt

            node.physicsBody?.angularVelocity = velocity

            // Update angle and time
            startingAngle = angle
            startingTime = touch.timestamp
        }
    }
}

override func touchesEnded(_ touches: Set<UITouch>, with event: UIEvent?) {
    startingAngle = nil
    startingTime = nil
}

但是当我将SKShapeNode（我的didMove函数内部）更改为圆圈时，这是不行的 - 这是更改的代码：

    override func didMove(to view: SKView) {
    let ball = SKShapeNode(circleOfRadius: 200)
    ball.fillColor = SKColor.red
    ball.position = CGPoint(x: self.frame.size.width/2, y: self.frame.size.height/2)
    ball.name = "BALL"
    ball.physicsBody = SKPhysicsBody(circleOfRadius: 200)
    ball.physicsBody?.angularDamping = 0.25
    ball.physicsBody?.pinned = true
    ball.physicsBody?.affectedByGravity = false
    self.addChild(ball)

}

有没有人看到/知道我的错误是什么？

Answer 1

你怎么能看到形状在转动？你在shapenode里面有什么东西，你可以看到旋转的纹理吗？

旋转圆形的shapenode看起来与静态的相同。在场景的更新循环中抓住球并打印其zRotation以查看它是否实际转动。

override func update(_ currentTime: TimeInterval) {
    var ball: SKShapeNode = childNodeWithName("BALL") as SKShapeNode
    print(ball.zRotation)
}

（这段代码是在没有访问Swift的情况下编写的，因此您可能需要稍微修改一下语法）

请记住，zRotation是以弧度为单位，所以它可能看起来不怎么样，但它正在改变，然后SKShapeNode实际上正在旋转，你只是看不到它。你必须添加一个可见的子节点。

无法围绕固定点旋转圆形节点

1 个答案: