使用SKCameraNode和SKConstraint创建可滚动的游戏地图

Question

我正在尝试创建可滚动的游戏地图（类似于“糖果迷恋地图导航”）。我正在尝试通过创建一个包含摄像机的不可见播放器节点（mapNavigator）来遵循Apple demo bots摄像机的教程。但是，我回来的数字似乎不正确。

有人可以澄清一下数学如何工作吗？

当前情况：

http://www.giphy.com/gifs/iDOEEgXqz12aqgIDXC

代码我试图用以下方式约束摄像机

override func didMove(to view: SKView) {
        super.didMove(to: view)
        addChild(mapNavigator)
        mapNavigator.addChild(mapCamera)
        camera = mapCamera
        constraintCamera()
    }

    override func update(_ currentTime: TimeInterval) {
        mapCamera.position = mapNavigator.position
    }

    override func touchesMoved(_ touches: Set<UITouch>, with event: UIEvent?) {
        guard let touch = touches.first else {
            return
        }

        let location = touch.location(in: self)
        let previousLocation = touch.previousLocation(in: self)

        mapNavigator.position.x -= location.x - previousLocation.x
        mapNavigator.position.y -= location.y - previousLocation.y
    }

    private func constraintCamera() {
        guard let camera = camera,
            let mapTileNode = childNode(withName: "mapTileNode")
            else { return }

        let mapContentRect = mapTileNode.calculateAccumulatedFrame()

        let scaledSize = CGSize(width: size.width * camera.xScale, height: size.height * camera.yScale)

        let xInset = min(scaledSize.width / 2, mapContentRect.width / 2)
        let yInset = min(scaledSize.height / 2, mapContentRect.height / 2)
        let insetContentRect = mapContentRect.insetBy(dx: xInset, dy: yInset)

        let xRange = SKRange(lowerLimit: insetContentRect.minX, upperLimit: insetContentRect.maxX)
        let yRange = SKRange(lowerLimit: insetContentRect.minY, upperLimit: insetContentRect.maxY)
        let levelEdgeConstraint = SKConstraint.positionX(xRange, y: yRange)
        levelEdgeConstraint.referenceNode = mapTileNode

        camera.constraints = [levelEdgeConstraint]
        mapNavigator.constraints = [levelEdgeConstraint]
    }