UW News

April 8, 2010

PhotoCity, virtual game of capture-the-flag, happening now on UW campus

UW News

It’s an intercollegiate challenge that’s a little bit different. No balls, sticks or stadiums are involved. Any number of people can participate. The playing field is the entire campus. And the only equipment you need is a digital camera.

The goal is to capture the campus, one photo at a time.

Until April 20, people will be snapping digital photos of the University of Washington campus in a game of virtual capture-the-flag. Students, faculty, staff and community members are all invited to participate.

The game, PhotoCity, is a project by computer scientists looking at ways to make 3-D models of neighborhoods or cities. An intercollegiate competition will pit the UW and Cornell University campuses.

To play, go to http://photocitygame.com to sign up. After registering you’ll see a campus map showing white flags that have yet to be captured, as well as colored flags that have already been claimed by one of four teams.

After learning how to play the game, take your camera and snap photos at an unclaimed flag’s location. You can submit photos instantly using the game’s iPhone application or upload photos later to the game’s Web site. Points are awarded for the number of photos, the resolution and quality of the images and, most importantly, whether a player was the first to capture a flag.

The game is being organized by researchers at the two universities who are using their own campuses to test a new strategy to acquire images for their models. At the end of three weeks the campus with the best reconstruction as judged by the research team will be declared the winner. Individual prizes will also be given for players who score the most points and capture the most flags.

“Our main goal is to get a giant 3-D reconstruction of the entire UW and Cornell campuses,” said PhotoCity developer Kathleen Tuite, a doctoral student in computer science and engineering. “For players, you’re adding geometry to a model and you’re creating a building out of nothing. You’re also gaining points, capturing flags and getting fame and glory for your team.”

If this first public test of PhotoCity is successful, it could provide a model to encourage residents to work together to acquire photos for digital reconstructions of neighborhoods or entire cities.

Zoran Popović, an associate professor of computer science and engineering, is Tuite’s adviser.

“Our lab is working on computer games that solve really hard problems,” Popović said. “In this case, it’s unusual compared to most computer games in that this has people going out into the real world instead of sitting in front of a computer. It’s not really known how addictive or how exciting it’s going to be, but it’s really a way to acquire data in a way that would not be possible any other way.”

The UW team is working with collaborators at Cornell University led by Noah Snavely, a graduate of the UW’s computer science department and now an assistant professor of computer science at Cornell. Snavely’s doctoral research at the UW created Photo Tourism, a tool that combines photos posted on the photo-sharing Web site, Flickr, to create 3-D models. That technology is licensed to Microsoft as the basis for the free tool Photosynth.

Researchers at UW and Cornell have been working together to push Photo Tourism’s limits, to create higher resolution and city-scale models. But relying on tourist photos meant that gaps remained in places that were less photogenic.

They hope that PhotoCity may help fill those gaps.

“There are people walking around with cameras all the time, and if just a small percent of them took helpful pictures of buildings from the right angles, then we could potentially build up a 3-D model of a city in a very fast, cost-effective and hopefully fun way,” Snavely said.

Players will get to compete individually, on teams at each campus and between campuses.

“We’re hoping to publish a paper on the effectiveness of PhotoCity as a way to create a 3-D replica of the entire urban world,” Popović said.

And, of course, to beat Cornell.


For more information, contact Popovic at 206-543-4226 or zoran@cs.washington.edu, Tuite at 206-616-7045 or ktuite@cs.washington.edu and Snavely at 607-255-4280 or snavely@cs.cornell.edu.

More information on the contest is at http://photocitygame.com/competition.php. The iPhone app is at http://itunes.apple.com/us/app/photocity/id341994556?mt=8.