This sample app runs an ARKit world tracking session with content displayed in a SceneKit view. To demonstrate plane detection, the app visualizes both the estimated shape of and a bounding rectangle for each detected ARPlaneAnchor object. On supported devices, ARKit can recognize many types of real-world surfaces, so the app also labels each detected plane with identifying text.
Configure and Run the AR Session
The ARSCNView class is a SceneKit view that includes an ARSession object that manages the motion tracking and image processing required to create an augmented reality (AR) experience. However, to run a session you must provide a session configuration.
The ARWorldTrackingConfiguration class provides high-precision motion tracking and enables features to help you place virtual content in relation to real-world surfaces. To start an AR session, create a session configuration object with the options you want (such as plane detection), then call the runWithConfiguration:options: method on the session object of your ARSCNView instance:
Run your session only when the view that will display it is onscreen.
Place 3D Content for Detected Planes
After you’ve set up your AR session, you can use SceneKit to place virtual content in the view.
When plane detection is enabled, ARKit adds and updates anchors for each detected plane. By default, the ARSCNView class adds an SCNNode object to the SceneKit scene for each anchor. Your view’s delegate can implement the renderer:didAddNode:forAnchor: method to add content to the scene. When you add content as a child of the node corresponding to the anchor, the ARSCNView class automatically moves that content as ARKit refines its estimate of the plane’s position.
ARKit offers two ways to track the area of an estimated plane. A plane anchor’s geometry describes a convex polygon tightly enclosing all points that ARKit currently estimates to be part of the same plane (easily visualized using ARSCNPlaneGeometry). ARKit also provides a simpler estimate in a plane anchor’s extent and center, which together describe a rectangular boundary (easily visualized using SCNPlane).
ARKit continually updates its estimates of each detected plane’s shape and extent. To show the current estimated shape for each plane, this sample app also implements the renderer:didUpdateNode:forAnchor: method, updating the ARSCNPlaneGeometry and SCNPlane objects to reflect the latest information from ARKit.
On iPhone XS, iPhone XS Max, and iPhone XR, ARKit can also classify detected planes, reporting which kind of common real-world surface that plane represents (for example, a table, floor, or wall). In this example, the renderer:didUpdateNode:forAnchor: method also displays and updates a text label to show that information.