Shadow casting panels
This technique seems to be a proof-of-concept for a thesis in CAAD (computer-aided architectural design) at ETH Zurich. Note that the panel could just as easily be the side of a building and the moving light source could be the sun.
Shadow Casting Panels (SCP) is a novel way for storing and presenting multiple images using one physical object. The images to be stored in a panel are first rasterized and converted to a black-and-white format, and then jointly encoded into the panel. More precisely, the images are considered in a pixel-by-pixel manner, and for each pixel of the an appropriate building block is placed at the corresponding place in the panel. The type of the block depends on the colors of the particular pixel in the images to be encoded. The actual blocks can have various geometries, yielding a variety of possible designs and perceptions.