This WorldAnchor is used to lock the surface into place relative to real world objects. It will be filled in when calling RequestMeshAsync to generate data for a surface and returned with the SurfaceDataReadyDelegate.
This anchor allows the device to lock the corresponding surface in place relative to real world objects as its knowledge of the real world changes. All generated mesh data will be local to this coordinate system. The outputAnchor parameter is required when calling RequestMeshAsync since spatial mapping meshes are intended to map the real world.