Interesting.  I usually tune my cars at both spa and silverstone.  Have noticed for a while that when the track is loading and you have to wait for entry, quick options, setup, replay, exit, etc. - that's when the track shows things like the above for a second.  Never happens on track, though.  The pavement on that track has unbelievable texture and detail.  I have a feeling that has something to do with it.