Apologies if this has been covered, but I'm not quite sure how to phrase the question.
I'm trying to achieve an effect similar to this: http://www.youtube.com/watch?v=TW6_X9qBeds I have 5 planes arranged to give the appearance of a cube recessed inside of an AR pattern. For the effect to be believable, the outside of the cube has to be invisible. However, I can't just use transparent materials on the backs because then you can see the inside of the cube. I guess what I'm looking for is a back-side material that is invisible, but does not offer a transparent view into the cube.
