ARWorldMap
The state in a world-tracking AR session during which a device maps the user’s position in physical space and proximity to anchor objects.
Declaration
class ARWorldMapMentioned in
Overview
The session state in a world map includes ARKit’s awareness of the physical space in which the user moves the device. ARKit uses the details of the user’s physical space to determine the device’s position and orientation, as well as any ARAnchor objects added to the session that can represent detected real-world features or virtual content placed by your app.
Serialize and Deserialize a World Map
When your app quits, you can save the current world map (acquired using getCurrentWorldMap(completionHandler:)). Because ARWorldMap conforms to NSSecureCoding, you serialize it using NSKeyedArchiver.
func writeWorldMap(_ worldMap: ARWorldMap, to url: URL) throws {
let data = try NSKeyedArchiver.archivedData(withRootObject: worldMap, requiringSecureCoding: true)
try data.write(to: url)
}To restore the world map the next time your app launches, use NSKeyedUnarchiver.
func loadWorldMap(from url: URL) throws -> ARWorldMap {
let mapData = try Data(contentsOf: url)
guard let worldMap = try NSKeyedUnarchiver.unarchivedObject(ofClass: ARWorldMap.self, from: mapData)
else { throw ARError(.invalidWorldMap) }
return worldMap
}You can use anchors from a resumed world map to place the same virtual content at the same positions from the saved session, if the app launches in the same physical environment.
For more information, see Saving and loading world data.
Share a Saved World Map
With two devices tracking the same world map, you can build a networked experience in which both users can see and interact with the same virtual content. To send an ARWorldMap to another device:
On one device, use NSKeyedArchiver to convert the world map to a data object. You don’t need to write the data to a file to send it over the network.
Use the networking technology of your choice to send the resulting data to another device. For example, in a Multipeer Connectivity session, call send(_:toPeers:with:) to send data, and implement doc://com.apple.documentation/documentation/multipeerconnectivity/mcsessiondelegate methods on the other device to receive data.
On the receiving device, use NSKeyedUnarchiver to instantiate an ARWorldMap from the data.
For more information, see Creating a multiuser AR experience.
Run a Deserialized World Map
To begin a new session from an existing ARWorldMap, set a world-tracking configuration’s initialWorldMap property and use run(_:options:). This starts a new session using the same spatial awareness and anchors loaded from the saved world map.