SKNode()对SKCropNode()子节点的衰落作用

Question

我有一个SKNode()，它有SKCropNode()子函数。我能够运行所有类型的动作来旋转和缩放我的SKNode()，但是当我想要使用任何类型的衰落动作时，结果总是alpha 1或alpha 0。不会褪色的。

通过将SKCropNode()替换为SKShapeNode()，衰落操作运行良好。

有人能告诉我为什么吗？难道不可能褪色隐藏的节点吗？

import SpriteKit

class GameScene: SKScene {

let player = SKNode()
let playerSize = CGFloat(50)
let playerCrop = SKCropNode()
let playerMask = SKSpriteNode(color: SKColor.blackColor(), size: CGSizeMake(CGFloat(100), CGFloat(100)))
let playerCircle = SKShapeNode(circleOfRadius: CGFloat(100))

let playerCenterMask = SKShapeNode(circleOfRadius: CGFloat(100))
let playerCenterCrop = SKCropNode()

override func didMoveToView(view: SKView) {

    backgroundColor = SKColor.blackColor()

    player.position = CGPoint(x:CGRectGetMidX(self.frame), y:CGRectGetMidY(self.frame))
    player.alpha = 0
    addChild(player)

    playerCenterMask.lineWidth = 20        
    playerCenterCrop.maskNode = playerCenterMask

    playerMask.position.x = -playerSize
    playerMask.position.y = playerSize
    playerCircle.lineWidth = 0
    playerCircle.fillColor = SKColor.redColor()
    playerCrop.addChild(playerCircle)
    playerCrop.maskNode = playerMask

    playerCenterCrop.addChild(playerCrop)
    player.addChild(playerCenterCrop)

    // Animations
    let playerScale = SKAction.scaleTo(2.0, duration: 5)
    let playerFadeIn = SKAction.fadeInWithDuration(5)
    let playerAnimation = SKAction.group([playerScale,playerFadeIn])

    player.runAction(playerAnimation, completion: {})

}

}

Answer 1

正如注释中提到的：SKCropNode使用alpha < 0.5来不绘制。>= 0.5绘制，您不能设置混合模式，所以它可能是做源混合模式。这意味着它正在覆盖阿尔法。孩子们后来就混在一起了。

播放机上下文被创建，它绘制给定的alpha，然后绘制SKCropNode，覆盖alpha而不是混合。

在你的孩子身上运行淡出动作，而不是你的父母来得到你想要的结果。

以下是您的源代码在更改时的样子：

import SpriteKit

class GameScene: SKScene {

    let player = SKNode()
    let playerSize = CGFloat(50)
    let playerCrop = SKCropNode()
    let playerMask = SKSpriteNode(color: SKColor.blackColor(), size: CGSizeMake(CGFloat(100), CGFloat(100)))
    let playerCircle = SKShapeNode(circleOfRadius: CGFloat(100))

    let playerCenterMask = SKShapeNode(circleOfRadius: CGFloat(100))
    let playerCenterCrop = SKCropNode()

    override func didMoveToView(view: SKView) {

        backgroundColor = SKColor.blackColor()

        player.position = CGPoint(x:CGRectGetMidX(self.frame), y:CGRectGetMidY(self.frame))
        player.alpha = 1
        addChild(player)
        playerCircle.alpha = 0
        playerCenterMask.lineWidth = 20
        playerCenterCrop.maskNode = playerCenterMask

        playerMask.position.x = -playerSize
        playerMask.position.y = playerSize
        playerCircle.lineWidth = 0
        playerCircle.fillColor = SKColor.redColor()
        playerCrop.addChild(playerCircle)
        playerCrop.maskNode = playerMask
        playerCenterCrop.addChild(playerCrop)
        player.addChild(playerCenterCrop)

        // Animations
        let playerScale = SKAction.scaleTo(2.0, duration: 5)
        let playerFadeIn = SKAction.fadeInWithDuration(5)
        let playerAnimation = playerScale

        player.runAction(playerAnimation, completion: {})
        playerCircle.runAction(playerFadeIn, completion: {})

    }

}