How calculate transform and position of SCNNode from .scn for area of ARSCNView

Question

I dont undestand how I can calculate SCNNode position on my ARSCNView with using Vision object. I have a detected face (VNFaceObservation) in ARSCNView, load node from .scn file. And I want that node was moving with face position.

I calculate 2D position of face bounding box with method:

private func faceFrameFrom(_ box: CGRect) -> CGRect {
    let origin = CGPoint(x: box.minX * sceneView.bounds.width, y: (1 - box.maxY) * sceneView.bounds.height)
    let size = CGSize(width: box.width * sceneView.bounds.width, height: box.height * sceneView.bounds.height)

    return CGRect(origin: origin, size: size)
}

and display UIView as sceneView subview with returned rect. It frame matches with face position.

After I load node from file, add node to scene.

I try calculate new position of node in method of scene session delegate:

func session(_ session: ARSession, didUpdate frame: ARFrame) 

But I dont understand how I should modify SCNNode position and create new SCNVector3. I think, that I should using sceneView.pointOfView?.simdWorld* properties for calculate offset, when device is moving or human with detected face is moving. But I dont sure that is true way

Any idea or algorithm for this calculation?