GIS and CG Integrated System for Automatic Generation of 3-D Building Models based on a Digital Map

Based on building polygons, we are proposing a GIS(Geographic Information System) and CG integrated system to generate multiple roofed 3-D building models automatically. Building polygons are buildings’ contours on the digital map stored by GIS. A 3-D urban model including 3-D building models is the important information infrastructure that can be utilized in several fields, such as landscape evaluation, urban planning, etc. However, in order to create 3-D building models, enormous time and labor have to be consumed to design the models. In order to automate the laborious process, the system aims at creating 3-D building models automatically from building polygons. Most building polygons’ edges meet at right angle( orthogonal polygon ). A complicated orthogonal polygon can be partitioned into a set of rectangles. After partitioning, the integrated system is placing rectangular roofs and building bodies on these rectangles. In order to partition an orthogonal polygon, we proposed a useful polygon expression in deciding from which vertex a dividing line (DL) is drawn. In this paper, we propose a scheme of prioritizing the DL that forms a branch roof, based on the length of the DL.