Introduction to ARKit

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last updated: 2016-08

Augmented Reality for iOS 11

ARKit enables a wide variety of augmented reality applications and games. This section covers the following topics:

Getting Started with ARKit

To get started with augmented reality, the following instructions walk through a simple application: positioning a 3D model and letting ARKit keep the model in place with its tracking functionality.

Jet 3D model floating in camera image

1. Add a 3D model

Assets should be added to the project with the SceneKitAsset build action.

SceneKit assets in a project

2. Configure the view

In the view controller's ViewDidLoad method, load the scene asset and set the Scene property on the view:

ARSCNView SceneView = (View as ARSCNView);

// Create a new scene
var scene = SCNScene.FromFile("art.scnassets/ship");

// Set the scene to the view
SceneView.Scene = scene;

3. Optionally implement a session delegate

Although not required for simple cases, implementing a session delegate can be helpful for debugging the state of the ARKit session (and in real applications, providing feedback to the user). Create a simple delegate using the code below:

public class SessionDelegate : ARSessionDelegate
{
  public SessionDelegate() {}
  public override void CameraDidChangeTrackingState(ARSession session, ARCamera camera)
  {
    Console.WriteLine("{0} {1}", camera.TrackingState, camera.TrackingStateReason);
  }
}

Assign the delegate in the in the ViewDidLoad method:

// Track changes to the session
SceneView.Session.Delegate = new SessionDelegate();

4. Position the 3D model in the world

In ViewWillAppear, the following code establishes an ARKit session and sets the position of the 3D model in space relative to the device's camera:

// Create a session configuration
var configuration = new ARWorldTrackingConfiguration {
  PlaneDetection = ARPlaneDetection.Horizontal,
  LightEstimationEnabled = true
};

// Run the view's session
SceneView.Session.Run(configuration, ARSessionRunOptions.ResetTracking);

// Find the ship and position it just in front of the camera
var ship = SceneView.Scene.RootNode.FindChildNode("ship", true);

ship.Position = new SCNVector3(2f, -2f, -9f);

Each time the application is run or resumed, the 3D model will be positioned in front of the camera. Once the model is positioned, move the camera and watch as ARKit keeps the model positioned.

5. Pause the augmented reality session

It is good practice to pause the ARKit session when the view controller is not visible (in the ViewWillDisappear method:

SceneView.Session.Pause();

Summary

The above code results in a simple ARKit application. More complex examples would expect the view controller hosting the augmented reality session to implement IARSCNViewDelegate, and additional methods be implemented.

ARKit provides lots of more sophisticated features, such as surface tracking, and user interaction. See the UrhoSharp demo for an example combining ARKit tracking with UrhoSharp.

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