Quick Tip: Geolocated Lens, Compass Heading, Magnetic North

aidan · July 2023

Hi all, I learned if you wait for the ARSession to be ready you can update its configuration information! This means you can set worldAlignment to .gravityAndHeading so your Lens lines up with true North instead of the arbitrary orientation of your phone which opens up the possibility to do map-based AR applications. I've added the code to CustomizedCameraController.swift

@State var arSessionInput = ARSessionInput();

self.cameraKit.start(
     input: avSessionInput,
     arInput: arSessionInput,
     cameraPosition: .back,
     videoOrientation: orientation,
     dataProvider: self.configureDataProvider(),
     hintDelegate: self,
     textInputContextProvider: textInputContextProvider,
     agreementsPresentationContextProvider: agreementsPresentationContextProvider
)

waitForSession()

func waitForSession() {
     if arSessionInput.session.currentFrame != nil {
          print("session ready!");
          let newConfiguration = ARWorldTrackingConfiguration()
          newConfiguration.worldAlignment = .gravityAndHeading
          arSessionInput.session.run(newConfiguration) 
     } else {
          DispatchQueue.main.asyncAfter(deadline: .now() + 0.01) {
               self.waitForSession()
          }
     }
}

It's a rough workaround but it gets the result! FYI you may have to setup location services and other permissions and settings beforehand for this to work.

aidan · July 2023

Bonus: if you'd like to get your Lens camera's x,y,z coordinates you can do so with the following. I'm using this to update the user's geolocation with finer precision

func getARPosition () {
        if let currentFrame = self.arSessionInput.session.currentFrame {
            let cameraTransform = currentFrame.camera.transform
            let cameraPosition = cameraTransform.columns.3
            let x = cameraPosition.x
            let y = cameraPosition.y
            let z = cameraPosition.z
            print("Camera position: (\(x), \(y), \(z))")
        } else {
            print("Unable to access current frame")
        }
    }

arashp · July 2023

Thank you for your awesome post @aidan. I am guessing it would be useful to get a callback when ARSession is ready so that the app doesn't have to wait and poll?

aidan · July 2023

@arashp possibly! I think what would be more useful in this specific instance is the ability to input custom settings into ARSessionInput(session:ARSession) before initializing CameraKit. Maybe it's possible but I find it overrides the values I set