This reminds me of dual photography [1], in which you trade many projectors and one camera for one projector and many cameras using time reversal symmetry. The

This reminds me of dual photography [1], in which you trade many projectors and one camera for one projector and many cameras using time reversal symmetry. The video [2] gives a good explanation, and the revelation of the playing card is what strikes me as similar to revealing reflected hidden faces. [1] http://graphics.stanford.edu/papers/dual_photography/ http://graphics.stanford.edu/papers/dual_photography/ [2] https://www.youtube.com/watch?v=p5_tpq5ejFQ https://www.youtube.com/watch?v=p5_tpq5ejFQ