SceneConfiguration.swift

import UIKit
import ARKit
import SceneKit

class ARViewController: UIViewController{

  // First we create instances of ARSCNView, ARSession and ARWorldTracking configuration
  let sceneView: ARSCNView = {
      let scene = ARSCNView()
      scene.translatesAutoresizingMaskIntoConstraints = false
      return scene
  }()
  
  let session = ARSession()
    
  let sessionConfiguration: ARWorldTrackingConfiguration = {
      let config = ARWorldTrackingConfiguration()
      config.planeDetection = .horizontal
      return config
  }()
  
  //In viewDidLoad we setup our sceneView, there are plenty of options we can use to configure our scene
  override func viewDidLoad(){
      sceneView.delegate = self
      sceneView.session = session
      sceneView.automaticallyUpdatesLighting = true
      sceneView.autoenablesDefaultLighting = true
      sceneView.preferredFramesPerSecond = 60
  }
  
  //We use lifecycle methods viewWillAppear and viewWillDisappear to control when will our session start and pause
  override func viewWillAppear(_ animated: Bool) {
      super.viewWillAppear(animated)
      session.run(sessionConfiguration, options: [.removeExistingAnchors, .resetTracking])
  }
    
  override func viewWillDisappear(_ animated: Bool) {
      super.viewWillDisappear(animated)
      session.pause()
  }
  
}