To communicate these ideas I project a movie onto a large wall/surface. At the same time I project a brighter pixelated movie that is reminiscent of the sun. This projected light is so bright it washes out the movie from the other projector. The “sunlike” projector is about waist height so that as soon as you walk in front of the light, the persons shadow hits the screen and reveals the video inside their shadow. The more people inside, the more of the video they can see.
More at: directedplay.com/hiddenlight.html