Fading action of SKNode() with SKCropNode() children - swift

Question

I have a SKNode() which has SKCropNode() children. I am able to run all kind of actions to rotate and scale my SKNode(), but when I want to use any kind of fading actions the result always is alpha 1 or alpha 0. No way of fading.
By replacing the SKCropNode() with a SKShapeNode() the fading action is working fine.
Can anyone tell my why? Isn't it possible to fade masked nodes?
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

As mentioned in the comments:
SKCropNode uses alpha < 0.5 to not draw. >= 0.5 to draw, and you can't set the blend mode, so it is probably doing source blend mode. Which means it is overwriting the alpha. Children afterwards get blended.
The player context is created, it draws at the given alpha, then the SKCropNode is drawn, overwriting alpha instead of blending.
Run the fade in action on your child, not your parent to get the results you are looking for.
Here is what your source looks like with changes:
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: {})
}
}