title: Use SCNNode as render "mask"?
body: <p>Is it possible to cause a node to render "clear" such that when in is drawn, any views underneath the scene view are shown where the node would normally be shown?</p>
  
  <p>For example, assume that our SCNView has a red UIView behind it. Using a sphere as an example, you would see a circular "hole" in the scene view where the the red view would show through.</p>
  
  <p>Any ideas? Would this involve a shader of some sort?</p>