SpriteKit中拖拽SKShapeNode如何避免穿越其他节点边界？

我需要实现拖拽代表玩家的圆形SKShapeNode小球时，不能穿越由复杂UIBezierPath创建的天花板、地板SKShapeNode边界，比如小球拖到天花板时不会穿墙。

游戏场景里，天花板和地板在update(_ currentTime: TimeInterval)中修改x坐标实现动画，已配置好碰撞检测与接触测试，整体运行正常，但两种拖拽方法都有问题：

方法一：直接修改position属性 #

在touchesMoved中直接更新小球position：

override func touchesMoved(_ touches: Set<UITouch>, with event: UIEvent?) {
  let translation = CGVector(dx: location.x - previousLocation.x, dy: location.y - previousLocation.y)
        var newPosition = ball.position 
        newPosition.x += translation.dx
        newPosition.y += translation.dy
        ball.position = newPosition
}

• 优点：拖拽流畅，和手指移动同步，慢速拖动时能遵守边界
• 缺点：快速拖动时小球会直接穿过天花板或地板

方法二：使用applyImpulse施加冲量 #

通过给小球physicsBody施加冲量实现拖拽：

override func touchesMoved(_ touches: Set<UITouch>, with event: UIEvent?) {
                guard let touch = touches.first, let location = touchLocation else { return }
                let newLocation = touch.location(in: self)
                let scalingFactor: CGFloat = 0.1
                let touchMovement = CGVector(dx: newLocation.x - location.x, dy: newLocation.y - location.y)
                touchForce = CGVector(dx: touchMovement.dx * scalingFactor, dy: touchMovement.dy * scalingFactor)
                touchLocation = newLocation
                ball.physicsBody?.applyImpulse(touchForce!)
}

• 优点：能遵守边界
• 缺点：有缓动效果，不符合预期的拖拽体验，也无法准确反映拖拽幅度

我需要兼顾两者优点的解决方案，以下是墙壁和小球的参考代码：

天花板/地板节点代码 #

class Wall: SKShapeNode {
    init(size: CGSize) {
        super.init()
        let bottomPath = UIBezierPath()
        bottomPath.move(to: CGPoint(x: 0, y: -19.99))
        bottomPath.addLine(to: CGPoint(x: 5723.5, y: -19.99))
        bottomPath.addLine(to: CGPoint(x: 5723.5, y: 35.51))
        bottomPath.addLine(to: CGPoint(x: 4915.5, y: 35.51))
        bottomPath.addCurve(to: CGPoint(x: 4892.87, y: 44.88), controlPoint1: CGPoint(x: 4907.01, y: 35.51), controlPoint2: CGPoint(x: 4898.87, y: 38.88))
       /// 更多路径节点

        bottomPath.close()
        self.path = bottomPath.cgPath
        strokeColor = UIColor.green
        fillColor = UIColor.clear
        lineWidth = 5
        lineCap = .round
        lineJoin = .round
        zPosition = 0
        name = "bottom"
        physicsBody = SKPhysicsBody(edgeLoopFrom: self.path!)
        physicsBody?.isDynamic = false
        physicsBody?.affectedByGravity = false
        physicsBody?.categoryBitMask = 1
        physicsBody?.contactTestBitMask = 2
        physicsBody?.collisionBitMask = 1
        physicsBody?.restitution = 0
        physicsBody?.usesPreciseCollisionDetection = true
        physicsBody?.density = 100
        physicsBody?.mass = 100
    }
}

小球节点代码 #

class Ball: SKShapeNode {
    convenience init(radius: CGFloat) {
        self.init(circleOfRadius: radius)
        
        fillColor = .red
        zPosition = 0
        physicsBody = SKPhysicsBody(circleOfRadius: radius)
        physicsBody?.affectedByGravity = false
        physicsBody?.categoryBitMask = 2
        physicsBody?.contactTestBitMask = 1
        physicsBody?.collisionBitMask = 1
        physicsBody?.restitution = 1
        physicsBody?.usesPreciseCollisionDetection = true
    }
}

游戏核心玩法是拖拽小球沿路径移动，统计耗时和碰壁次数，求合适的拖拽方案兼顾流畅性与边界约束。

内容的提问来源于stack exchange，提问作者user499846