Which image is being used as reference in ARSceneView? - swift

Question

I am currently making an AR app that uses image tracking.
I want it to have 2 images in the reference images folder (Image A: ~670x210, and Image B: ~1123x794).
How do I check which image is the camera detecting?
For example, if the camera is seeing Image A - I want to make a plane twice the size of the physical object, if it's seeing Image B - I want to make the plane the same size as the physical object.
Here's a snippet of my code, if needed:
override func viewWillAppear(_ animated: Bool) {
super.viewWillAppear(animated)
// Create a session configuration
let configuration = ARImageTrackingConfiguration()
if let trackedImage = ARReferenceImage.referenceImages(inGroupNamed: "ARpaperImage", bundle: Bundle.main) {
configuration.trackingImages = trackedImage
configuration.maximumNumberOfTrackedImages = 1
}
// Run the view's session
sceneView.session.run(configuration)
}
// MARK: - ARSCNViewDelegate
func renderer(_ renderer: SCNSceneRenderer, nodeFor anchor: ARAnchor) -> SCNNode? {
let node = SCNNode()
if let imageAnchor = anchor as? ARImageAnchor {
let plane = SCNPlane(width: imageAnchor.referenceImage.physicalSize.width, height: imageAnchor.referenceImage.physicalSize.height)
plane.firstMaterial?.diffuse.contents = UIColor(white: 1.0, alpha: 0,5)
let planeNode = SCNNode(geometry: plane)
planeNode.eulerAngles.x = -.pi / 2
node.addChildNode(planeNode)
}
return node
}

Answer 1

An ARReferenceImage has a name property which you can use to determine which ReferenceImage has been detected which is simply:
A descriptive name for the image
As such when you put your ARReferenceImages into your resource bundle you can and (probably already have) given them a name e.g:
You can the use these names within the following delegate callback to handle your requirements.
func renderer(_ renderer: SCNSceneRenderer, didAdd node: SCNNode, for anchor: ARAnchor)
As such lets assume we have two ARReferenceImages called Brown and Choco. Using these names we can then create logic to display different content e.g:
//-------------------------
//MARK: - ARSCNViewDelegate
//-------------------------
extension ViewController: ARSCNViewDelegate{
func renderer(_ renderer: SCNSceneRenderer, didAdd node: SCNNode, for anchor: ARAnchor) {
//1. Check We Have Detected An ARImageAnchor
guard let validAnchor = anchor as? ARImageAnchor, let referenceImageName = validAnchor.referenceImage.name else { return }
//2. Get The Physical Size Of The Reference Image (This Is Specificed When You Create Your Target In The ARResource Bundle)
let physicalSizeOfReferenceImage = CGSize(width: validAnchor.referenceImage.physicalSize.width, height: validAnchor.referenceImage.physicalSize.height)
///3. Log The Data For Debugging Purposes
print("""
Detected ARAnchorID = \(validAnchor.identifier)
Detected Reference Image Name = \(referenceImageName)
Detected Reference Image Physical Size = (width) \(physicalSizeOfReferenceImage.width),
Detected Reference Image Physical Size = (height) \(physicalSizeOfReferenceImage.height)
""")
//4. Perform Instanciation & Other Login Based On The Reference Image Detected
if referenceImageName == "Brown"{
node.addChildNode(planeNodeOfSize(CGSize(width: physicalSizeOfReferenceImage.width * 2, height: physicalSizeOfReferenceImage.height * 2)))
}else if referenceImageName == "Choco"{
node.addChildNode(planeNodeOfSize(CGSize(width: physicalSizeOfReferenceImage.width, height: physicalSizeOfReferenceImage.height)))
}
}
/// Generates An SCNNode With An SCNPlaneGeometry Of A Specified Width & Height
///
/// - Parameter size: CGSize
/// - Returns: SCNNode
func planeNodeOfSize(_ size: CGSize) -> SCNNode{
//1. Create An SCNPlane Of Our Chosen Size
let planeNode = SCNNode()
let planeGeometry = SCNPlane(width: size.width, height: size.height )
planeGeometry.firstMaterial?.diffuse.contents = UIColor.white
planeNode.opacity = 0.25
planeNode.geometry = planeGeometry
//2. Rotate The PlaneNode To Horizontal
planeNode.eulerAngles.x = -.pi/2
//3. Return Our Node
return planeNode
}
}
Hope it helps...