In Swift/SpriteKit Can you use a ShapeNode as mask in a CropNode

Question

I've been trying to combine randomised SKShapeNode shapes with textures using a SKCropNode но это не похоже на работу. Я предполагаю что SKCropNodes only work with bitmap graphics such as PNG.

       //define sprite as crop node
       let cropSprite = SKCropNode()
       //create spriteNode with texture and add it
       let texSprite = SKSpriteNode(imageNamed: "rock")
       cropSprite.addChild(texSprite)
       //set mask of cropping Sprite to (predefined) shape node with .maskNode
       cropSprite.maskNode = myShapeNode
       //add final cropped sprite to scene
       self.addChild(cropSprite)

In this case nothing appears. If I don't set the:

cropNode.maskNode = myShapeNode

the cropSprite appears as a normal sprite with a texture added.

Есть идеи?

Большое спасибо, Кв