A simple ARSCN View Controller with full render delegate list.

ARViewController.swift

//
//  ARViewController.swift
//
//  Created by digitallysavvy.
//  Copyright © 2019 digitallysavvy All rights reserved.
//

import UIKit
import ARKit

internal class ARViewController: UIViewController, ARSCNViewDelegate, ARSessionDelegate {
    
    var sceneView : ARSCNView!
    var scnLights : [SCNNode] = []
      
    let debug : Bool = true                             // toggle the debug logs
    
    // MARK: VC Events
    override func loadView() {
        super.loadView()
        self.view.backgroundColor = UIColor.black       // set the background color
        
        // Setup sceneview
        let sceneView = ARSCNView() //instantiate scene view
        self.view.insertSubview(sceneView, at: 0)
        
        //add sceneView layout contstraints
        sceneView.translatesAutoresizingMaskIntoConstraints = false
        sceneView.topAnchor.constraint(equalTo: self.view.topAnchor).isActive = true
        sceneView.leftAnchor.constraint(equalTo: self.view.leftAnchor).isActive = true
        sceneView.rightAnchor.constraint(equalTo: self.view.rightAnchor).isActive = true
        sceneView.bottomAnchor.constraint(equalTo: self.view.bottomAnchor).isActive = true
        // set reference to sceneView
        self.sceneView = sceneView
    }
    
    override func viewDidLoad() {
        super.viewDidLoad()
        
        // set ARKit render and session delegates
        self.sceneView.delegate = self
        self.sceneView.session.delegate = self

        if debug {
            self.sceneView.debugOptions = [ARSCNDebugOptions.showWorldOrigin, ARSCNDebugOptions.showFeaturePoints, .showBoundingBoxes]
            self.sceneView.showsStatistics = true
        }
    }
    
    override func viewWillAppear(_ animated: Bool) {
        super.viewWillAppear(animated)
        // Configure ARKit Session
        let configuration = ARWorldTrackingConfiguration()  // ARKit trackign configuration
        configuration.planeDetection = [.horizontal, .vertical]
        configuration.providesAudioData = true              // enable audio data
        configuration.isLightEstimationEnabled = true       // enable light estimation (save on processing)

        self.sceneView.session.run(configuration)           // set cunfiguration for ARKit session
    }
    
    override func viewDidAppear(_ animated: Bool) {
        super.viewDidAppear(animated)
        let light = self.createLight(withPosition: SCNVector3(x: 0,y: 5,z: 0), andEulerRotation: SCNVector3(-Float.pi / 2, 0, 0))
        self.sceneView.scene.rootNode.addChildNode(light)
        self.scnLights.append(light)
    }
    
    override func viewWillDisappear(_ animated: Bool) {
        super.viewWillDisappear(animated)

        // Pause the view's session
        self.sceneView.session.pause()
        self.sceneView.removeFromSuperview()
        self.sceneView = nil
    }
    
    // MARK: Hide status bar
    override var prefersStatusBarHidden: Bool {
        return true
    }
    
    // MARK: Render delegate
    func renderer(_ renderer: SCNSceneRenderer, willRenderScene scene: SCNScene, atTime time: TimeInterval) {
        guard let currentFrame = self.sceneView.session.currentFrame else { return }
        let intensity : CGFloat = currentFrame.lightEstimate!.ambientIntensity / 1000.0
        self.sceneView.scene.lightingEnvironment.intensity = intensity
        if scnLights.count > 0 {
            for node in scnLights {
                node.light?.intensity = intensity
            }
        }
        
        // do something when scene will render
    }
    
    func renderer(_ renderer: SCNSceneRenderer, updateAtTime time: TimeInterval) {
        // do something on render update
    }
    
    func renderer(_ renderer: SCNSceneRenderer, didRenderScene scene: SCNScene, atTime time: TimeInterval) {
        
    }
    
    // plane detection
    func renderer(_ renderer: SCNSceneRenderer, didAdd node: SCNNode, for anchor: ARAnchor) {
        // anchor plane detection
    }
    
    // plane updating
    func renderer(_ renderer: SCNSceneRenderer, didUpdate node: SCNNode, for anchor: ARAnchor) {
        // anchor plane is updated
    }
    
    func renderer(_ renderer: SCNSceneRenderer, didRemove node: SCNNode, for anchor: ARAnchor) {
        // anchor plane is removed
    }
    
     // MARK: Session delegate
    func session(_ session: ARSession, didUpdate frame: ARFrame) {
         // ARSession did update
    }
    
    func session(_ session: ARSession, didOutputAudioSampleBuffer audioSampleBuffer: CMSampleBuffer) {
        // ARSession did output audio data
    }
    
    func session(_ session: ARSession, cameraDidChangeTrackingState camera: ARCamera) {
         // ARSession camera tracking state change
    }
    
    func sessionWasInterrupted(_ session: ARSession) {
         // ARSession was interrupted
    }
    
    func sessionInterruptionEnded(_ session: ARSession) {
        // ARSession interuption ended
    }
    
    func sessionShouldAttemptRelocalization(_ session: ARSession) -> Bool {
         // whether to attempt recovery of world-tracking state after an interruption.
        return true
    }
    
    
    
    // MARK: Lights
    func createLight(withPosition position: SCNVector3, andEulerRotation rotation: SCNVector3) -> SCNNode {
        // Create a directional light node with shadow
        let directionalNode : SCNNode = SCNNode()
        directionalNode.light = SCNLight()
        directionalNode.light?.type = SCNLight.LightType.directional
        directionalNode.light?.color = UIColor.white
        directionalNode.light?.castsShadow = true
        directionalNode.light?.automaticallyAdjustsShadowProjection = true
        directionalNode.light?.shadowSampleCount = 64
        directionalNode.light?.shadowRadius = 16
        directionalNode.light?.shadowMode = .deferred
        directionalNode.light?.shadowMapSize = CGSize(width: 1024, height: 1024)
        directionalNode.light?.shadowColor = UIColor.black.withAlphaComponent(0.5)
        directionalNode.position = position
        directionalNode.eulerAngles = rotation
        
        return directionalNode
    }

}