spinning light drawing images on the retina

We've all seen a train or a car whizzing past us in the night. If it's close enough and we don't move our heads rather quickly, we see that its lights appear as horizontal lines instead of moving dots. This is due to a characteristic of our eyes known as Persistence of Vision. A retina is capable of changing the data it sends to the brain only so fast. A quickly moving light appears to be in many places at once. If it's on continuously, we see a solid line. If it's flashing, we see a line of dots. This phenomenon can be thought of as the brain having a limited "frame rate". Movies "work" only because of this limitation. We only think we're seeing fluid motion around us because the brain is so good at piecing bits of data into continuous images and stories.

Spin uses Persistence of Vision to create the illusion of a cylindrical digital display (computer screen), 12 feet tall and 12 feet in diameter. Vertical columns of multi-color LED (light emitting diode) clusters spin around a vertical axis at 90 revolutions per minute. At a radius of 6 feet, they move at 41 miles per hour. 2880 LEDs are turned on and off by a computer in precise synchronization with the rotation of the columns, creating the illusion of a cylindrical digital display. Spin has a vertical resolution of 16 pixels (picture elements), each of which can display one of 8 colors. As horizontal position is determined by time in Spin, the horizontal resolution is theoretically infinite, but for the sake of data manipulation efficiency it is be limited to 360 pixels all the way around the cylinder.

Spin was created in the first half of 2000 and was presented at The Burning Man Festival in August and September. It ran for a few minutes, then after re-starting it suffered a mechanical breakdown that couldnŐt be fixed in the desert. Spin was re-built to better survive the elements and successfully ran for hours at the Burning Man Decompression party in October of 2000.

The images that Spin displays are simple graphics and text. Complicated sequences of animated images are created with a computer program and saved to files for later playback on Spin. This program was made available to anyone in the world via the World Wide Web. In the months preceding The Burning Man Festival, nearly 100 such sequences were emailed to me by Burning Man participants. Receiving these contributions was an unexpectedly exciting part of the experience of building Spin. People came up with all kinds of clever animation tricks that I had never even dreamed of. It was of course pretty exciting for them too, to see their work up there in spinning lights. This program is still available, and in fact has been much improved since last year. You can download it here.

free software for making Spin sequences


best photo from Solstice 2000

best photo from Decompression 2000

best photo from BurningMan 2000

photos of setup at Burning Man 2000


My goal for Spin in 2001 is to develop ways of getting new content to display on Spin, and ways of making it more interactive. Towards both these ends, I am making improvements to the Spin software:

Matt Peterson and Chris Petrell intend to once again put into service a wireless LAN (local area network) in Black Rock City this year. This creates some very interesting possibilities for Spin. The computers that control Spin use the same wireless technology as the LAN. What Chris and Matt and I have discussed is creating web pages within the LAN at which participants could draw pictures or type some text, or perhaps create full-blown Spin animations. When they are done, they press a "Submit" button, which sends their creation to SpinŐs queue. If Spin is running, it will automatically play these creations first-come, first-served. These web pages would be accessible by any computer on the LAN, which includes a number of kiosks that Chris and Matt intend to put up, and any private laptops that care to be connected. Thus, Spin becomes an interactive, communal art-space and message board for the entire city, enabling any participant to share his or her creativity and humor.

See you on the playa!
Christopher Schardt