Semi-Automated and Interactive Construction of 3D Urban Terrains

We have developed a set of tools that attack the problem of rapid construction of 3D urban terrains containing buildings, roads, trees, and other features. Heretofore, the process of creating such databases has been painstaking, with no integrated set of tools to model individual buildings, apply textures, place objects accurately with respect to other objects, and insert them into a database structure appropriate for real-time display. Since fully automated techniques for routinely building 3D urban environments using machine vision have not yet been entirely successful, our approach has been to build a set of semiautomated tools that support and make efficient a human interpreter, running on a PC under Windows NT. The tools use remote sensing technologies and thus are applicable to the general case of not having close access to urban data (e.g., collections of buildings may be in foreign or hostile environments), but can use close-up image data if provided. Once we have the 3D urban model, we face the problems of final precise alignment of objects and real-time visualization. We attack both problems by providing an interface to VGIS 1 , our high-resolution global terrain visualization system. Typically data from different sources, such as phototextures, building models, maps, and terrain elevations, do not register precisely when put together. VGIS provides accurate, real-time display of all these data products. Our tools provide a porting mechanism for bringing the urban data into VGIS where it can be interactively aligned. The data are then organized into a VGIS database for real-time display.