title: Tracking multiple images and play their videos in ARkit2
body: <p>I've got below sample code, tracking a single image then plays a video using Apple's ARkit.
  Currently videos stored locally on the device.
  The code below just tracks a single image and plays corresponding video.
  How can I modify it and let it track multiple images and play their videos?</p>
  
  <pre><code> @IBOutlet var sceneView: ARSCNView!
  
  // Create video player
  let videoPlayer: AVPlayer = {
      // Load cat video from bundle
      guard let url = Bundle.main.url(forResource: "nyan-cat", withExtension: "mp4", subdirectory: "art.scnassets") else {
          print("Could not find video file")
          return AVPlayer()
      }
  
      let player = AVPlayer(url: url)
  
      NotificationCenter.default.addObserver(forName: NSNotification.Name.AVPlayerItemDidPlayToEndTime, object: nil, queue: nil) { notification in
          player.seek(to: CMTime.zero)
          player.play()
      }
      return player
  }()
  
  func renderer(_ renderer: SCNSceneRenderer, nodeFor anchor: ARAnchor) -&gt; SCNNode? {
      let node = SCNNode()
  
      // Show video overlayed to image
      if let imageAnchor = anchor as? ARImageAnchor {
  
          // Create a plane
          let plane = SCNPlane(width: imageAnchor.referenceImage.physicalSize.width,
                               height: imageAnchor.referenceImage.physicalSize.height)
  
          // Set AVPlayer as the plane's texture and play
          plane.firstMaterial?.diffuse.contents = self.videoPlayer
          self.videoPlayer.play()
  
          let playNode = SCNNode(geometry: plane)
  
          // Rotate the plane to match the anchor
          playNode.eulerAngles.x = -.pi / 2
  
          // Add plane node to parent
          node.addChildNode(playNode)
      }
  
      return node
  }
  </code></pre>