How do i detect multiple images in AR? - ios

Question

I am creating this live newspaper app with ARKit which transforms images on newspaper into videos.I am able to detect one image and play a video on it but when i try doing it on two images and play a corresponding video on that images i get an error like
Attempted to add a SKNode which already has a parent
I tried by checking tracked images and comparing them to reference images but i think something is wrong with my logic.
This is my ViewDidAppear() Method
override func viewWillAppear(_ animated: Bool) {
super.viewWillAppear(animated)
// Create a session configuration
let configuration = ARImageTrackingConfiguration()
if let trackedImages = ARReferenceImage.referenceImages(inGroupNamed: "NewsPaperImages", bundle: Bundle.main) {
configuration.trackingImages = trackedImages
configuration.maximumNumberOfTrackedImages = 20
}
// Run the view's session
sceneView.session.run(configuration)
}
func renderer(_ renderer: SCNSceneRenderer, nodeFor anchor: ARAnchor) -> SCNNode? {
let node = SCNNode()
if let imageAnchor = anchor as? ARImageAnchor {
if(imageAnchor.referenceImage == UIImage(named: "Image2_River")) {
self.videoNode = SKVideoNode(fileNamed: "riverBeauty.mp4")
}
print("Yes it is an image")
self.videoNode.play()
let videoScene = SKScene(size: CGSize(width: 480, height: 360))
videoNode.position = CGPoint(x: videoScene.size.width/2, y: videoScene.size.height/2)
videoNode.yScale = -1.0
videoScene.addChild(videoNode)
let plane = SCNPlane(width: imageAnchor.referenceImage.physicalSize.width, height: imageAnchor.referenceImage.physicalSize.height)
plane.firstMaterial?.diffuse.contents = videoScene
let planeNode = SCNNode(geometry: plane)
planeNode.eulerAngles.x = -.pi/2
node.addChildNode(planeNode)
}
return node
}
it should be playing video on every detected image but instead it crashes.

Answer 1

Looking at your code, and from what you have said I think that you need to change your logic, to create a Video Node using the name property of your ARReferenceImage instead.
When you create an ARReferenceImage either statically (within the ARResourceBundle) or dynamically you can assign it a name e.g:
Then you can use the names to add logic to assign a different video to each referenceImage detected.
And in order to keep your code DRY you could create a reusable function to create your video node.
As such a simple example might look something like so:
//-------------------------
//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 else { return }
//2. Create A Video Player Node For Each Detected Target
node.addChildNode(createdVideoPlayerNodeFor(validAnchor.referenceImage))
}
/// Creates An SCNNode With An AVPlayer Rendered Onto An SCNPlane
///
/// - Parameter target: ARReferenceImage
/// - Returns: SCNNode
func createdVideoPlayerNodeFor(_ target: ARReferenceImage) -> SCNNode{
//1. Create An SCNNode To Hold Our VideoPlayer
let videoPlayerNode = SCNNode()
//2. Create An SCNPlane & An AVPlayer
let videoPlayerGeometry = SCNPlane(width: target.physicalSize.width, height: target.physicalSize.height)
var videoPlayer = AVPlayer()
//3. If We Have A Valid Name & A Valid Video URL The Instanciate The AVPlayer
if let targetName = target.name,
let validURL = Bundle.main.url(forResource: targetName, withExtension: "mp4", subdirectory: "/art.scnassets") {
videoPlayer = AVPlayer(url: validURL)
videoPlayer.play()
}
//4. Assign The AVPlayer & The Geometry To The Video Player
videoPlayerGeometry.firstMaterial?.diffuse.contents = videoPlayer
videoPlayerNode.geometry = videoPlayerGeometry
//5. Rotate It
videoPlayerNode.eulerAngles.x = -.pi / 2
return videoPlayerNode
}
}
As you can see I have opted to use an AVPlayer as my video content, although you can continue to use your videoScene should you so desire.
Hope it points you in the right direction...