When you run a world-tracking AR session and specify ARReferenceObject objects for the session configuration's detectionObjects property, ARKit searches for those objects in the real-world environment. When the session recognizes an object, it automatically adds to its list of anchors an ARObjectAnchor for each detected object.
To place virtual 3D content that matches the position or size of the detected object, use the anchor's inherited transform property together with the center and extent of the anchor's referenceObject.
The detected object referenced by the object anchor.