3-D City Modeling System Unveiled
Wednesday, February 25, 2004
Two UC Berkeley researchers have paved the way for students to play computer games in cities that resemble their hometowns. UC Berkeley electrical engineering and computer science professor Avideh Zakhor and postdoctoral research engineer Christian Frueh have presented a fast approach to automated generation of textured three-dimensional city models.
By building a system consisting of two 2-D laser scanners and a video camera, Zakhor and Frueh were able to acquire 3-D models of building facades as seen from the ground level.
"We mounted this system on a Chevy pickup truck and simply drove around and recorded data," Frueh said. "Specifically, we captured the geometry of the facades with the 2-D laser scanner, and we captured the visual appearance with a video camera."
Aerial images were taken from a helicopter, with airborne laser scans provided by a Los Angeles company.
The creation of this new approach captured a model of 12 downtown Berkeley blocks in approximately 25 minutes of driving time. An added advantage of merging ground-based and airborne views, Frueh added, is that it costs only a tenth of the price of a 3-D scanner.
Creating 3-D city models has many potential applications.
"It enables architects to envision a building facade, adding and subtracting buildings as they work. Other city groups that can use it include the police and fire departments," said Zakhor, the principal investigator of the study. "In the event of terrorist attacks or other emergies, one can visualize the scene with help from these 3-D city models."
In addition to urban planning, which would greatly aid city architects, the models can advance car navigation. Driving directions would be more understandable with visuals helping drivers picture the city street by street.
"Special effects companies need 3-D city models for movies such as The Matrix," Frueh said. "And I'm sure a lot of people would be interested in playing their favorite computer game in ‘their' city, say Berkeley, instead of in an artificial setting."
The research is part of an ongoing investigation initiated out of military interest. Though it is possible to obtain models for large-scale environments, capturing the details from small-scale environments has proved difficult. Residential areas, for example, are more difficult to record because of more trees blocking the view from the ground level. In order to include fine details, more manual work is needed.
"One can only reconstruct building tops but not facades from aerial images, which make the models unusable for walk-or drive-throughs," Frueh said. As a result, stereo vision techniques are applied to aerial or satellite imagery.
The research allows for creativity. Downtown Berkeley and Telegraph Avenue scenes were used as part of the research published in the International Journal of Computer Vision as well as IEEE Computer Graphics and Applications' Special Issue.
"I found it amazing how real some parts of our models look like, and all the small details you can see. When I drive down on University Avenue, I keep looking and thinking ‘It really looks like our models ...'" Frueh said.
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