How to add a semi-transparent background on top of camera ARKit - swift

Question

I'm trying to add a semi transparent background that cover my camera view from ARKit.
I try different things :
Add background to sceneView.scene but that not support transparency
Add an overlaySKScene but nodes on my scene are overlayed too.
Use CIImage from session > capturedImage but too slow.
Use this post : Reliable access and modify captured camera frames under SceneKit, it's OK for transform to Black And White but I don't understand how I can keep colors and blend gray color.
Search on OpenGL or Metal but I'm a noob !
So, do you have an idea to realize that operation in ARKit ?
Thanks in advance.

Answer 1

You can do it this way:
import ARKit
class ViewController: UIViewController,
ARSCNViewDelegate {
#IBOutlet var sceneView: ARSCNView!
override func viewDidLoad() {
super.viewDidLoad()
sceneView.delegate = self
sceneView.session.delegate = self
let scene = SCNScene()
sceneView.scene = scene
let planeNode = SCNNode()
planeNode.geometry = SCNPlane(width: 100,
height: 100)
planeNode.geometry?.firstMaterial?.diffuse.contents = UIColor(white: 0,
alpha: 0.9)
planeNode.position.z = -5 // 5 meters away
sceneView.pointOfView?.addChildNode(planeNode) // PINNING TO CAMERA
}
override func viewWillAppear(_ animated: Bool) {
super.viewWillAppear(animated)
let configuration = ARWorldTrackingConfiguration()
sceneView.session.run(configuration)
}
override func viewWillDisappear(_ animated: Bool) {
super.viewWillDisappear(animated)
sceneView.session.pause()
}
}
... or in extension:
extension ViewController: ARSessionDelegate {
func session(_ session: ARSession,
didUpdate frame: ARFrame) {
let planeNode = SCNNode()
planeNode.geometry = SCNPlane(width: 100,
height: 100)
planeNode.position.z = -5
planeNode.geometry?.firstMaterial?.diffuse.contents = UIColor(white: 0,
alpha: 0.9)
// var translation = matrix_identity_float4x4
// translation.columns.3.z = -5
// planeNode.simdTransform = matrix_multiply(translation,
// frame.camera.transform)
sceneView.pointOfView?.addChildNode(planeNode)
}
}