ios - 如何将两个 SKTextures 合二为一

Question

我正在尝试为游戏创建背景并有两个背景图像。我可以使用两个不同的 SKSpriteNode()、SKTexture、SKAction.sequence..etc 和一些数学将它们拼接在一起，但结果有点不稳定，而且我似乎无法正确地计算数学。它们应该能够组合成一个长期变化的背景，但它总是抵消。

谁能告诉我如何将两种纹理合二为一，这样我就不必为数学问题费脑筋了。或者，如果有人发现我的数学有错误，您能指出来吗？两个背景具有相同的 1200 像素宽度

override func didMoveToView(view: SKView) {
    /* Setup your scene here */

    var bgTexture = SKTexture(imageNamed: "bg_2_midground_1.png")
    var bgTexture2 = SKTexture(imageNamed: "bg_2_midground_2.png")

    var totalBG = bgTexture.size().width + bgTexture2.size().width

    var moveBG1 = SKAction.moveByX(-bgTexture.size().width, y: 0, duration: 12)
    //shift bg back to be able to repeat itself
    var replaceBG1 = SKAction.moveByX(bgTexture.size().width, y: 0, duration: 0.0) //move immediately back to replace self
    var moveBG1Forever = SKAction.repeatActionForever(SKAction.sequence([moveBG1,replaceBG1]))

    var moveBG2 = SKAction.moveByX(-bgTexture2.size().width, y: 0, duration: 12)
    //shift bg back to be able to repeat itself
    var replaceBG2 = SKAction.moveByX(bgTexture2.size().width, y: 0, duration: 0.0) //move immediately back to replace self
    var moveBG2Forever = SKAction.repeatActionForever(SKAction.sequence([moveBG2,replaceBG2]))

    for var i:CGFloat = 0; i<2; i++ {
        var bg = SKSpriteNode(texture: bgTexture)
        var bg2 = SKSpriteNode(texture: bgTexture2)

        bg.position = CGPointMake(bgTexture.size().width/2.0 + bgTexture.size().width * i + bgTexture2.size().width * i, CGRectGetMidY(self.frame))
        bg2.position = CGPointMake(bgTexture.size().width/2.0 + bgTexture2.size().width + bgTexture2.size().width * 2 * i, CGRectGetMidY(self.frame))

        bg.runAction(moveBG1Forever)
        bg2.runAction(moveBG2Forever)

        self.addChild(bg)
        self.addChild(bg2)

        println(bg.position)
        println(bgTexture.size().width)

        println(bg2.position)
        println(bgTexture2.size().width)
    }

Answer 1

不使用 SKActions，您可以使用 update 函数将所有背景节点一起移动，当每个节点离开屏幕时立即将每个节点移动到末尾。

为了使事情更易于管理，我们可以创建自定义背景 SKNode。

class BackgroundNode : SKNode
{
    override init() {
        super.init()

        var bgTexture1 = SKTexture(imageNamed: "b1.jpg")
        var bgTexture2 = SKTexture(imageNamed: "b2.png")


        let totalBG = bgTexture1.size().width + bgTexture2.size().width

        for index in 0..<2
        {
            var bg1 = SKSpriteNode(texture: bgTexture1)
            var bg2 = SKSpriteNode(texture: bgTexture2)
            bg1.anchorPoint = CGPointMake(0, 0)
            bg2.anchorPoint = CGPointMake(0, 0)

            let i = CGFloat(index)

            bg1.position = CGPointMake(i * bgTexture1.size().width + i * bgTexture2.size().width, 0)
            bg2.position = CGPointMake((i+1) * bgTexture1.size().width + i * bgTexture2.size().width, 0)

            self.addChild(bg1)
            self.addChild(bg2)
            lastNode = bg2
        }
    }

    required init?(coder aDecoder: NSCoder) {
        super.init(coder: aDecoder)
    }

    var speedOfBackground : CGFloat = 300.0
    var previousTime : CFTimeInterval = -1
    var lastNode : SKSpriteNode!

    func update(currentTime: CFTimeInterval) {

        if previousTime != -1
        {
            var outOfBoundsSprite : SKSpriteNode? = nil
            let deltaX = speedOfBackground * CGFloat(currentTime - previousTime)
            for sknode in self.children
            {
                if let sprite = sknode as? SKSpriteNode
                {
                    sprite.position = CGPointMake(sprite.position.x - deltaX, sprite.position.y)
                    if (sprite.position.x < -sprite.size.width)
                    {
                        outOfBoundsSprite = sprite
                    }
                }
            }
            if (outOfBoundsSprite != nil)
            {
                outOfBoundsSprite?.position.x = lastNode.position.x + lastNode.size.width
                lastNode = outOfBoundsSprite!
            }
        }
        previousTime = currentTime
    }

}

您可以改变 speedOfBackground 属性来改变移动速度。

它可以像这样在SKScene中使用

class GameScene: SKScene ,SKPhysicsContactDelegate {

    var background : BackgroundNode!

    override func didMoveToView(view: SKView) {

        background = BackgroundNode()
        background.speedOfBackground = 500.0
        self.addChild(background)
    }


    override func update(currentTime: CFTimeInterval) {
        background.update(currentTime)
    }
}