title: Surface shader result can't be recorded in ARKit
body: <p>I record the scene where I play a video ver a SCNPlane in which I remove green background of video using surface shader. This cause recorded video to have a white background instead of transparent one. I'm not using ReplayKit to record the scene, I'm using off screen SCNRenderer to record snapshots. Any ideas why shader result is not recorded?
  You can see the ARSNCView preview and recording below.</p>
  <p><a href="https://i.stack.imgur.com/ea1cL.jpg" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/ea1cL.jpg" alt="preview" /></a>
  <a href="https://i.stack.imgur.com/99rU1.png" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/99rU1.png" alt="recording" /></a></p>
  <p>Device Model: iPhone mini running iOS 15
  Xcode Version: Xcode 13
  iOS Version: iOS 15</p>