The new tallest building on the San Francisco skyline — and the tallest building in America west of the Mississippi — includes a nine-story electronic sculpture that’s been called the tallest piece of public art on Earth. It uses 11,000 LED bulbs reflected off the tower-topping aluminum panels — each pixel created by a set of red, green, blue and white lights controlled by 8-bit PIC microcontrollers. “On a clear night, the show is visible for 30 miles,” reports IEEE Spectrum.

Slashdot reader Tekla Perry shares their article about “the technology involved in the light show at the top of Salesforce Tower. Electrical engineer and artist Jim Campbell explains it all — and how the window-washer problem stumped him for nearly a year.”
“[O]n the 62nd floor, a central PC-based computer runs Ubuntu Linux, sending instructions to a communications control system that splits the data and sends it at 11 Mbit to the 32 enclosures using a custom communications protocol… We will capture images throughout the day, sending them to Amazon’s cloud, and run some algorithms designed to identify visual interesting-ness. For example, at its simplest, when we look at the sky, if it’s all blue, it’s boring, if it’s all white, it’s boring, if it has white and blue it is likely to be interesting. We’ll chose the best half hour of the day at each camera, based on movement and color, to display….”

And finally, when the main display shuts down late at night, another system designed by Campbell will kick in. In this static display, a set of 36 white LEDs will create a three-dimensional constellation of lights that will look like stars. “It’s quieter, it has a random aspect to it,” he says.

“Since construction started, the tower has emerged as an icon of the new San Francisco — techie, ambitious, perhaps a little grandiose,” writes the New Yorker, capturing the moment when Campbell finally unveiled his four-year project — while fighting stomach flu and a chest cold, on a night which turned out to be prohibitively foggy. The executive vice-president of Boston Properties told him cheerily, “Jim! Look on the brighter side. We’ve got every night for the rest of our lives.”

“There was a long silence from the people on the terrace. The fog was thick. At last, someone exclaimed, ‘Woo-hoo!,’ and a volley of cheers followed.” Although the colors they were seeing came from the celebratory fireworks and not from Jim’s light sculpture.
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Source:: Slashdot