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The Salesforce Tower, the second tallest building west of the Mississippi, has already redefined the San Francisco skyline. Now it will take the concept of public art to new heights.

Starting tonight, 11,000 LEDs will project an ever-changing visual display on the six-story crown of the building. The screen will be fed in part by cameras around the city that survey the bay, the weather and activity in a local park.

Jim Campbell, the artist in charge, calls it “Day for Night.” As the city winds down for the evening, it will catch a glimpse of where it has been.

“The images will be very abstract — clouds, ocean waves,” Mr. Campbell said. “I don’t like street scenes much because they have the feel of a security camera.” But he’s also experimenting with prerecorded images, including dancers from Alonzo King Lines Ballet, a local company.