将多个蒙版分配给SKCropNode

Question

作为一个例子，我有一个圆圈向左移动，然后在屏幕上向右移动。我希望圆只有在两个特定方块（maskNodes）内时才可见。我正在使用SKCropNode来尝试实现这一点，但SKCropNode掩码只允许我分配一个掩码。有没有人知道给SKCropNode分配两个或多个掩码的方法，或者甚至可以这样做。谢谢！

override func didMoveToView(view: SKView) { 

    anchorPoint = CGPointMake(0.5, 0.5) 
    backgroundColor = UIColor.whiteColor() 

    let mask1 = SKSpriteNode(color: UIColor.blackColor(), size: CGSizeMake(50, 50)) 
    mask1.position.x = -100 

    let mask2 = SKSpriteNode(color: UIColor.blackColor(), size: CGSizeMake(50, 50)) 
    mask2.position.x = 100 

    let cropNode = SKCropNode() 
    cropNode.maskNode = mask1 // && mask2 
    addChild(cropNode) 

    let circle = SKShapeNode(circleOfRadius: 25) 
    circle.fillColor = UIColor.blackColor() 
    cropNode.addChild(circle) 


    // Move Circle 

    let moveLeft = SKAction.moveToX(-frame.size.width/2, duration: 2) 
    let moveRight = SKAction.moveToX(frame.size.width/2, duration: 2) 
    let seq = SKAction.repeatActionForever(SKAction.sequence([moveLeft, moveRight])) 

    circle.runAction(seq) 

} 

Answer 1

想出来，只需将两个掩码添加到父项，然后将父项指定为SKCropNode掩码。

override func didMoveToView(view: SKView) { 

    anchorPoint = CGPointMake(0.5, 0.5) 
    backgroundColor = UIColor.whiteColor() 

    let maskParent = SKSpriteNode() 

    let mask1 = SKSpriteNode(color: UIColor.blackColor(), size: CGSizeMake(50, 50)) 
    mask1.position.x = -100 
    maskParent.addChild(mask1) 

    let mask2 = SKSpriteNode(color: UIColor.blackColor(), size: CGSizeMake(50, 50)) 
    mask2.position.x = 100 
    maskParent.addChild(mask2) 

    let cropNode = SKCropNode() 
    cropNode.maskNode = maskParent 

    addChild(cropNode) 

    let circle = SKShapeNode(circleOfRadius: 25) 
    circle.fillColor = UIColor.blackColor() 
    cropNode.addChild(circle) 

    // Move Circle 

    let moveLeft = SKAction.moveToX(-frame.size.width/2, duration: 2) 
    let moveRight = SKAction.moveToX(frame.size.width/2, duration: 2) 
    let seq = SKAction.repeatActionForever(SKAction.sequence([moveLeft, moveRight])) 

    circle.runAction(seq) 

}