Вы не кормили arView
объектом session
.
let session = ARSession()
self.arView.session = session
Код должен выглядеть следующим образом:
let arView = ARView(frame: .zero)
guard let config = arView.session.configuration as? ARWorldTrackingConfiguration
else { print("Can't run this configuration...") }
guard ARWorldTrackingConfiguration.supportsFrameSemantics(.personSegmentationWithDepth)
else { print("People Occlusion feature isn't supported.") }
config.frameSemantics.insert(.personSegmentationWithDepth)
arView.session.run(config)