Abstract
Building polygons are buildings' contours on the digital map stored by GIS. Based on building polygons, we are proposing a GIS and CG integrated system to generate 3-D building models automatically. A 3-D urban model is the important information infrastructure that can be utilized in several fields, such as landscape evaluation, urban planning, disaster prevention simulation, etc. To realize a 3-D urban model, it is important to generate building models efficiently. However, in order to realize a 3-D urban model, time consuming process is necessary to acquire the spatial data and to design the models. In order to automate the laborious process, the system aims at creating 3-D building models automatically from building polygons. If the building polygon with more than 4 vertices has right angle only, then it can be divided in rectangles. We propose the useful polygon expression where the building polygon can be expressed as a set of its edges' turning direction (RL expression) and that decides from which vertex a dividing line (DL) is drawn.
