How can you track the position of the camera using RealityKit? Several examples are using SceneKit, but I found none using RealityKit. I need a function such as:
func session(_ session: ARSession, didUpdate frame: ARFrame) {
// Do something with the new transform
let currentTransform = frame.camera.transform
doSomething(with: currentTransform)
}
Using ARView Camera Transform:
You can access the ARView Camera Transform using the following method:
var cameraTransform: Transform
The transform of the currently active camera.
So assuming your ARView was called arView you could access the Transform like so:
let cameraTransform = arView.cameraTransform
A more useful implementation however would be to enable your ARView to observe SceneEvents.Updateby making use of the following:
subscribe(to:on:_:)
func subscribe<E>(to event: E.Type, on sourceObject: EventSource? = nil, _ handler: @escaping (E) -> Void) -> Cancellable where E : Event
Which means you would have an observer of any:
event triggered once per frame interval that you can use to execute custom logic for each frame.
To do that you would:
Firstly import the Combine Framework.
You would then create a Cancellable variable:
var sceneObserver: Cancellable!
Then in ViewDidLoad add something like the following:
sceneObserver = arView.scene.subscribe(to: SceneEvents.Update.self) { [unowned self] in self.updateScene(on: $0) }
Whereby each update calls the following:
/// Callback For ARView Update Events
/// - Parameter event: SceneEvents.Update
func updateScene(on event: SceneEvents.Update) {
print(arView.cameraTransform)
}
Using ARSessionDelegate:
Alternatively you can access the ARCamera from within RealityKit by subscribing to the ARSessionDelegate e.g:
arView.session.delegate = self
And then registering for the following callback:
func session(_ session: ARSession, didUpdate frame: ARFrame)
Whereby a working example would look something like this:
extension ViewController: ARSessionDelegate {
func session(_ session: ARSession, didUpdate frame: ARFrame) {
guard let arCamera = session.currentFrame?.camera else { return }
print("""
ARCamera Transform = \(arCamera.transform)
ARCamera ProjectionMatrix = \(arCamera.projectionMatrix)
ARCamera EulerAngles = \(arCamera.eulerAngles)
""")
}
}
Hope it points you in the right direction.