March 9, 2010

Cornell Professor Helps Develop New 3-D Photo Visualization Game

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There is no need to travel to New York to see Saint Patrick’s Cathedral next week; just log onto the internet and visit PhotoCity. The website, which is subtitled, “Capture the world, one photo at a time,” was created in part by Prof. Noah Snavely, computer science.

Snavely wrote his doctoral thesis — “Scene Reconstruction and Visualization from Internet Photo Collections” — about a set of algorithms he and researchers from the University of Washington developed to take flat photos and turn them into three-dimensional models.

The PhotoCity game utilizes this original set of algorithms developed by Snavely and Profs. Zoran Popovic, Kathleen Tuite and Dun-Yu Hsaio’s, computer science, University of Washington. The algorithms are used to make virtual 3-D worlds. So far, the game has ten locations, including Cornell University.

Players join teams on the website and earn points by taking pictures of under-represented buildings on the game. The set of algorithms then pick up on certain features of a picture and try to find them in other pictures of the same building, thus creating the 3-D model.

For example, the ILR conference center is currently missing some parts of its building in the 3-D world. These sides of the building are given white flags; a white flag denotes a place on a building where no pictures have yet been taken. It is here that players can earn the most points because each photo upload adds 3-D points, which then translates into game points.

Snavely says the game was inspired by his past research and is part of a new vision in gaming. “There’s a new trend in casual games called ‘Games With a Purpose,’ where people perform useful tasks — like taking pictures for 3D modeling — through a game. The trick is to make the task actually fun,” Snavely said. Gautam Kamath ’12 is an engineering student who has worked closely with Snavely on the PhotoCity project.

He finds the ability to create a “virtual copy of the entire world” highly engaging. “With the reconstruction you can visit places you have never seen to some extent. Through the imaging on PhotoCity I can visit the Coliseum in Rome without having to buy the plane ticket,” Kamath said.

Kamath also believes that having the game open to the public is key in helping to develop more complex imaging of not only Cornell’s campus, but also other areas around the country. “By allowing anyone to play PhotoCity and upload pictures, we can cover more ground. We are, essentially, creating a virtual Cornell and hoping to keep extending our reach to other areas,” Kamath said.

Snavely’s original research, the set of algorithms that takes flat images and turns them into three-dimensional models, was used by Microsoft to create Photosynth. Photosynth works much like PhotoCity where the public can upload photos of places they have been and create an almost cinematic quality.

The effect of “synthing” is that of standing in front of a large screen and watching a setting unfold in front of you. Snavely believes that PhotoCity can keep growing to build 3-D models of all the cities in the world.

“By adding new viewpoints to the game, players are actually contributing information that is used to reconstruct new parts of a building in 3D, and so our knowledge of the shape of the buildings in the world grows over time,” Snavely said. “As computer vision algorithms for 3-D reconstruction get better, we can reuse the data we’ve already collected to build better 3-D models.”

Original Author: Erika Hooker