A session-unique identifier for the BoundedPlane that subsumed this plane.
If SubsumedById is not TrackableId.InvalidId, then this BoundedPlane has been merged into the BoundedPlane with the TrackableId specified by SubsumedById. This can happen, for example, when two parts of the same surface are initially detected as separate planes. As the physical space is explored, the device may determine that the two planes actually represent the same surface.
Note: Not all platforms support this feature. Unity provides the information where available.
See Also: BoundedPlane, XRPlaneSubsystem, XRPlaneSubsystem.TryGetPlane