Earlier quoted context omitted.
It was called Aerial 3D [0] it was mentioned in OP article in a link. [0] https://www.google.com/amp/s/techcrunch.com/2011/11/15/aeria...
Yeah that link has zero explanation of depth control.
My guess/assumption is intersecting beams.
Or maybe it is just an energy distance thing. Not sure what happened to this company.
Aerial Burton 3D is the name