Developing an ARKit app that leaves text for others to view - ios

Question

I am creating an iOS AR app that sets text in a specific location and leaves it there for others to view. Is there a better way to implement it than what I am doing?
Currently, I have it set so that the text is saved to Firebase and loads it by setting the nodes relative to the camera’s position. I’m wondering if there is a way to save ARAnchors in a fashion similar to what I am doing but is that possible?
My current function for saving the text to the location via a user tapping the screen:
/*
* Variables for saving the user touch
*/
var touchX : Float = 0.0
var touchY : Float = 0.0
var touchZ : Float = 0.0
override func touchesBegan(_ touches: Set<UITouch>, with event: UIEvent?) {
// will be used for getting the text
let textNode = SCNNode()
var writing = SCNText()
// gets the user’s touch upon tapping the screen
guard let touch = touches.first else {return}
let result = sceneView.hitTest(touch.location(in: sceneView), types: [ARHitTestResult.ResultType.featurePoint])
guard let hitResult = result.last else {return}
let hitTransform = SCNMatrix4.init(hitResult.worldTransform)
let hitVector = SCNVector3Make(hitTransform.m41, hitTransform.m42, hitTransform.m43)
// saves X, Y, and Z coordinates of touch relative to the camera
touchX = hitTransform.m41
touchY = hitTransform.m42
touchZ = hitTransform.m43
// Was thinking of adding the ability to change colors. Probably can skip next seven lines
var colorArray = [UIColor]()
colorArray.append(UIColor.red)
writing = SCNText(string: input.text, extrusionDepth: 1)
material.diffuse.contents = colorArray[0]
writing.materials = [material]
// modifies the node’s position and size
textNode.scale = SCNVector3(0.01, 0.01, 0.01)
textNode.geometry = writing
textNode.position = hitVector
sceneView.scene.rootNode.addChildNode(textNode)
// last few lines save the info to Firebase
let values = ["X" : touchX, "Y" : touchY, "Z" : touchZ, "Text" : input.text!] as [String : Any]
let childKey = reference.child("Test").childByAutoId().key
if input.text != nil && input.text != "" {
let child = reference.child("Test").child(childKey!)
child.updateChildValues(values)
} else {
let child = reference.child("Test").child(childKey!)
child.updateChildValues(values)
} // if
} // override func
/*
* Similar to the previous function but used in next function
*/
func placeNode(x: Float, y: Float, z: Float, text: String) -> Void {
let textNode = SCNNode()
var writing = SCNText()
let hitVector = SCNVector3Make(x, y, z)
touchX = x
touchY = y
touchZ = z
var colorArray = [UIColor]()
colorArray.append(UIColor.red)
writing = SCNText(string: text, extrusionDepth: 1)
material.diffuse.contents = colorArray[0]
writing.materials = [material]
textNode.scale = SCNVector3(0.01, 0.01, 0.01)
textNode.geometry = writing
textNode.position = hitVector
sceneView.scene.rootNode.addChildNode(textNode)
} // func
/*
* This next function is used in my viewDidLoad to load the data
*/
func handleData() {
reference.child("Test").observeSingleEvent(of: .value, with: { (snapshot) in
if let result = snapshot.children.allObjects as? [DataSnapshot] {
for child in result {
let xCoord = Float(truncating: child.childSnapshot(forPath: "X").value as! NSNumber)
let yCoord = Float(truncating: child.childSnapshot(forPath: "Y").value as! NSNumber)
let zCoord = Float(truncating: child.childSnapshot(forPath: "Z").value as! NSNumber)
let inscription = child.childSnapshot(forPath: "Text").value
self.placeNode(x: xCoord , y: yCoord , z: zCoord , text: inscription as! String)
} // for
} // if
}) // reference
} // func
I have looked into a few things such as ARCore but that looks like it uses Objective-C. I’ve made this app in Swift and I am not sure if I can incorporate ARCore with how I have implemented my current application.
Do I just need to get over it and learn Objective-C? Can I still work with what I have?

Answer 1

I think that ARCore anchors are only available for 24 hours, so that could be a problem.
You probably need to use ARKit2.0's ARWorldMap and save it as data on firebase for others to see the text in the same place, otherwise you are assuming in your code that future users will start their AR session in the exact same position and direction as the person who left the text. You probably need to use core location first to see where in the world the user is.