SpriteKit：顺时针旋转船绕一圈

Question

在 SpriteKit 中，我想定位一个宇宙飞船精灵，以便：

(a) 顺时针或逆时针旋转。

(b) 精灵旋转，鼻子始终指向中心，无论它在圆上的哪个位置。

目前我有这个输出：

...

我的理想输出如图

我的代码如下：

class 游戏场景：SKScene {

lazy var circleNode:SKShapeNode = {
    var circle = SKShapeNode(circleOfRadius: 200)
    circle.position = CGPoint(x: frame.midX, y: frame.midY)
    circle.strokeColor = SKColor.purple
    circle.lineWidth = 10.0
    circle.glowWidth = 2.0
    circle.physicsBody?.isDynamic = false
    return circle
}()

lazy var shipNode: SKSpriteNode = {
    var sprite = SKSpriteNode(imageNamed: "ship")
    sprite.position = CGPoint(x: circleNode.frame.minX, y: circleNode.frame.minY)
    sprite.xScale = 2
    sprite.yScale = 2
    sprite.zPosition = 1
    return sprite
}()

class func newGameScene() -> GameScene {
    // Load 'GameScene.sks' as an SKScene.
    guard let scene = SKScene(fileNamed: "GameScene") as? GameScene else {
        print("Failed to load GameScene.sks")
        abort()
    }

    // Set the scale mode to scale to fit the window
    scene.scaleMode = .aspectFill

    return scene
}    

func setUpScene() {
    self.addChild(circleNode)
    self.addChild(shipNode)
}

override func didMove(to view: SKView) {
    self.setUpScene()
}

override func touchesMoved(_ touches: Set<UITouch>, with event: UIEvent?) {

    let touch = touches.first
    if let location = touch?.location(in: self){
        if location.x > shipNode.position.x {
            let moveToRight = SKAction.moveBy(x: 1, y: 0, duration: 5)
            let forever = SKAction.repeatForever(moveToRight)
            shipNode.run(forever, withKey: "move")
        }else{
            let moveToLeft = SKAction.moveBy(x: -1, y: 0, duration: 5)
            let forever = SKAction.repeatForever(moveToLeft)
            shipNode.run(forever, withKey: "move")
        }
    }

}

override func touchesEnded(_ touches: Set<UITouch>, with event: UIEvent?) {
    shipNode.removeAction(forKey: "move")
}

}

我尝试添加一个SKAction.follow

   func setUpScene() {
        self.addChild(circleNode)
        self.addChild(shipNode)


        let circularMove = SKAction.follow(circleNode.path!, asOffset: false, orientToPath: true, duration: 5)
        shipNode.run(SKAction.repeat(circularMove,count: 2))

    }

但这里的问题是它在路径周围自行设置动画，这不是我想要的。相反，只有用户触摸才能让船顺时针或逆时针移动。

我如何确保：

(a) 精灵坐在圆形路径上 (b) 精灵的鼻子总是指向圆心

非常感谢

Answer 1

您可以通过将您的船添加到一个容器（一个 SKNode），将船定位在圆上的一个点（0 度），将船指向圆心来实现这一点，然后旋转容器。这是一个例子...

let sprite = SKSpriteNode(imageNamed:"your_ship_name")
let container = SKNode()

override func didMove(to view:SKView) {
    let numRotations:CGFloat = 100
    let circleRadius:CGFloat = 200

    addChild(container)
    // Rotate so the ship initially points to the center
    sprite.zRotation = CGFloat.pi/2
    sprite.position = CGPoint(x: circleRadius, y: 0)
    container.addChild(sprite)

    let rotate = SKAction.rotate(byAngle: 2 * CGFloat.pi * numRotations, duration: 5 * TimeInterval(numRotations))

    container.run(rotate.reversed())
}

SpriteKit：顺时针旋转船绕一圈

SpriteKit: Rotate a ship clockwise around a circle

sprite-kit

skaction