Recreate Rome in 1 day

Ancient Rome city was not built in a day. It took nearly a decade to build Collesseum, and for nearly a century to complete St. Peter's Church. But now the city, including those above, can be digitized for a few hours

The newly developed computer algorithm at the University of Washington uses hundreds of thousands of photos of other travelers to automatically reconstruct the entire city in about a day.

This is the latest in a series of tools developed at UW to exploit the growing number of digital photos on photo-sharing Web sites. 'Digitized' Rome is built from 150,000 photos associated with the keyword 'Rome' or 'Roma' downloaded from the famous photo sharing site, Flickr.

Computers analyzed each picture and in 21 hours combined them to create a 3D digital model. With this model the observer can fly around the city of Rome, from the Trevi Fountain to the Pantheon Temple to the inside of the Sistine church.

Sameer Agarwal, professor of computer science and engineering at UW and the lead author of the paper, was presented in October at the International Computer Vision Conference in Kyoto, Japan, saying: 'Doing How to combine giant photo collections together is a big challenge. So far, even if we have all the necessary equipment, recreating a city using such a large number of images can be very time consuming. '

Previous versions of UW's photo-linking technology are known as Photo Tourism. This technology was licensed to Microsoft in 2006, and now offers this tool for free under the name Photosynth.

Noah Snavely co-author, who developed Photo Tourism as his doctoral project at UW and is now a professor at Cornell University, said: 'With Photosynth and Photo Tourism, we can replicate each location individual. Here we are trying to create all the onions.

Colosseum is viewed digitally reconstructed. Each triangle shape is where a person stands when taking a picture. The shape of the building is determined by analyzing photographs taken from all different angles. (Photo: Washington University)

Other authors of the paper include Rick Szeliski of Microsoft Research, UW computer science professor Steve Seitz and graduate student Ian Simon at UW.

In addition to Rome, the team recreated the Croatian coast city, Dubrovnik, handling 60,000 photos in less than 23 hours using 350 computers; and Venice, Italy, handling 250,000 photos in 65 hours using 500 computers. Many historians regard Venice as a bright 'candidate' for digital preservation before the country harms the city further.

Moving from specific locations to the entire city - from hundreds of photos to hundreds of thousands of photos is not a simple thing. Previous versions of Photo Tourism combine each photo with all the remaining photos in one set. But when the number of photos increases, the number of photo pairs becomes too much. A set of 250,000 photos takes at least 1 year to process 500 computers. One million photos will take a decade.

Newly developed code works 100 times faster than previous versions. First it identifies the most suitable pairs of photos and focuses on those parts. The code also uses parallel processing techniques, enabling simultaneous running on multiple computers, or even on remote systems connected via the Internet.

New and faster code makes ambitious projects possible

Seitz said : 'If a city needs several months to recreate it is the same as building Rome. But in a day's time you can review all cities and start building their models. '

This new technology can create online maps that give viewers a virtual reality experience. Software can build cities for video games automatically. It can also be used in architecture to create digital preservation of cities, or in combination with online maps.

The research was funded by the National Science Foundation, Naval Research Laboratory and Spawar, Microsoft Research, and Google.