We've finally got our movie-playing technology sorted, which means we can at last show this video of Bitfall, the rain-printing machine developed by Julius Popp of Spherical Robots.
The movie shows the machine in action during the Nuit Blanche festival in Paris 2005. Above: simulation of Bitfall. Below: diagram showing how the magnetic valves produce water droplets that create moving imagery.
There's a short documentary about Popp and Bitfall over on YouTube. Popp's website is down at the moment so this description of Bitfall is from Information Aesthetics:
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Bitfall is "a physical water sculpture with 128 synchronized magnetic valves, so that a wall of falling water drops can be perceived as a graphical bitmap matrix. A computer application selects currently popular keywords from news websites, & displays them on the transparent 'information curtain'. the 'information flow' metaphor literally demonstrates the dynamic & ever-changing character of continuous information streams from which users build their associated experiences."