How to instantiate an ARSCNView - ios

Question

I would like to use ARKit to calculate the amount of ambient light that is in the current video frame. However after creating an ARSCNView object when I retrieve the current frame it returns a null value.
What am I doing wrong?
public class EyeAlignmentUICameraPreview : UIView, IAVCaptureVideoDataOutputSampleBufferDelegate
{
void Initialize()
{
CaptureSession = new CaptureSession();
PreviewLayer = new AVCaptureVideoPreviewLayer(CaptureSession)
{
Frame = Bounds,
VideoGravity = AVLayerVideoGravity.ResizeAspectFill
};
var device = AVCaptureDevice.GetDefaultDevice(AVCaptureDeviceType.BuiltInTelephotoCamera, AVMediaType.Video, AVCaptureDevicePosition.Back);
ARSCNView SceneView = new ARSCNView();
// frame is null after this line is executed
var frame = SceneView.Session.CurrentFrame;
}
}

Answer 1

Update my comment to answer for more details.
ARFrame
A video image and position tracking information captured as part of an AR session.
currentFrame
The video frame image, with associated AR scene information, most recently captured by the session.
According to these Apple ARKit Documentations, the currentFrame will have value when the ARSession get the video and associated AR scene information. So, we have to run the session at first.
To run the ARSession, we need a session configuration:
Running a session requires a session configuration: an instance of the ARConfiguration class, or its subclass ARWorldTrackingConfiguration. These classes determine how ARKit tracks a device's position and motion relative to the real world, and thus affect the kinds of AR experiences you can create.
Thus, the code snippet for ARSession running is like this:
public override void ViewWillAppear(bool animated)
{
base.ViewWillAppear(animated);
//Create a session configuration
var configuration = new ARWorldTrackingConfiguration
{
PlaneDetection = ARPlaneDetection.Horizontal,
LightEstimationEnabled = true
};
// Run the view's session
SceneView.Session.Run(configuration, ARSessionRunOptions.ResetTracking);
}