Thus Rome has been built in a single day, on a PC, using a method of image clustering, stereo, stereo fusion and structure from motion to give high computational performance.
It was devised by a team of researchers from the University of North Carolina at Chapel Hill and the Swiss university, ETH-Zurich, who believe the system will help preserve heritage sites, by allowing tourists to explore sites virtually.
Led by Jan-Michael Frahm, research assistant professor of computer science in the UNC College of Arts and Sciences, 3 million images of Rome available online were used to reconstruct all of the city's major landmarks.
Although the technique of using millions of photos to recreate detailed scenes has been demonstrated by other systems such as Microsoft's PhotoSynth, Frahm says they required clusters of computers to perform the necessary image analysis. Frahm said his team used a simple home PC equipped with four powerful graphics cards, giving an improvement of more than a factor of 1,000 over current commercial systems.
"Our technique would be the equivalent of processing a stack of photos as high as the 828-meter Dubai Towers, using a single PC, versus the next best technique, which is the equivalent of processing a stack of photos 42 meters tall - as high as the ceiling of Notre Dame - using 62 PCs," he said. "This efficiency is essential if one is to fully utilise the billions of user-provided images continuously being uploaded to the Internet."