Roof report from automatically generated 3D building models by straight skeleton computation

3D building models are important in several fields, such as urban planning and roof report for insurance industries. However, enormous time and labor has to be consumed to create these 3D models, using a 3D modeling software such as 3ds Max or SketchUp. In order to automate laborious steps, a GIS and CG integrated system is proposed for automatically generating 3D building models, based on building polygons (building footprints) on digital maps. Digital maps show most building polygons' edges meet at right angles (orthogonal polygon). In the digital map, however, not all building polygons are orthogonal. In either orthogonal or non-orthogonal polygons, the new system is proposed for automatically generating 3D building models with general shaped roofs by straight skeleton computation. In this paper, the algorithm for shrinking a polygon and forming a straight skeleton are clarified and, the new methodology is proposed for constructing roof models by assuming `the third event' and, at the end of the shrinking process, the shrinking polygon is converged to `a line of convergence'. In our research, extended straight skeleton computation is used for automatic generation of roof models. Based on the monotone polygons which straight skeleton computation forms, roof boards are automatically generated, and a top view of these roof boards can be a roof report for natural disaster damage.