Waterfalls have never been this much fun. Sheets of cascading droplets have been turned into a multilayered computer display, suitable for playing Tetris in 3D.
Peter Barnum, Srinivasa Narasimhan and Takeo Kanade at Carnegie Mellon University in Pittsburgh, Pennsylvania, have projected images onto a series of water screens, one behind the other, to give depth to the image.
Each screen is formed by water droplets falling from 50 stainless-steel needles. The needles release their droplets in unison, with 60 such lines created every second. A camera tracks their position and feeds the information to a projector, which illuminates them with pulses of light. The human eye integrates the information from several pulses to create the illusion of images moving on a floating screen.