The ancient city of Rome was not built in a day. It took nearly a decade to build the Colosseum, and almost a century to construct St. Peter's Basilica. But now the city, including these landmarks, can be digitized in just a matter of hours. A new computer algorithm developed at the University of Washington uses hundreds of thousands of tourist photos to automatically reconstruct an entire city in about a day. The tool is the most recent in a series developed at the UW to harness the increasingly large digital photo collections available on photo-sharing Web sites. The digital Rome was built from 150,000 tourist photos tagged with the word ‘Rome’ or ‘Roma’ that were downloaded from the popular photo-sharing Web site, Flickr. Computers analyzed each image and in 21 hours combined them to create a 3D digital model. With this model a viewer can fly around Rome's landmarks, from the Trevi Fountain to the Pantheon to the inside of the Sistine Chapel. Earlier versions of the UW photo-stitching technology are known as Photo Tourism. That technology was licensed in 2006 to Microsoft, which now offers it as a free tool called Photosynth. With Photosynth and Photo Tourism it is possible to reconstruct individual landmarks.
In addition to Rome, the team recreated the Croatian coastal city of Dubrovnik, processing 60,000 images in less than 23 hours using a cluster of 350 computers, and Venice, Italy, processing 250,000 images in 65 hours using a cluster of 500 computers. Many historians see Venice as a candidate for digital preservation before water does more damage to the city, the researchers said. Previous versions of the Photo Tourism software matched each photo to every other photo in the set. But as the number of photos increases the number of matches explodes, increasing with the square of the number of photos. A set of 250,000 images would take at least a year for 500 computers to process. A million photos would take more than a decade. The newly developed code works more than a hundred times faster than the previous version. It first establishes likely matches and then concentrates on those parts. The code also uses parallel processing techniques, allowing it to run simultaneously on many computers, or even on remote servers connected through the Internet. This technique could create online maps that offer viewers a virtual-reality experience. The software could build cities for video games automatically, instead of doing so by hand. It also might be used in architecture for digital preservation of cities, or integrated with online maps. The research was supported by the National Science Foundation, the Office of Naval Research and its Spawar lab, Microsoft Research, and Google.
More information:
http://uwnews.org/article.asp?articleID=51970
More information:
http://uwnews.org/article.asp?articleID=51970