There are many useful applications of three dimensional polyhedral building models, such as visualization, light, sound, energy, or fire simulations, and cost analysis. Unfortunately, construction of polyhedral building models using currently available modeling software is a tedious process that involves considerable human effort, and often results in topologically incorrect or incomplete models. This paper describes a system called the Building Model Generator (BMG), that creates correct 3D polyhedral building models from architectural floor plans, while requiring minimal user interaction.

Two-dimensional architectural floor plans are a standard format for expressing the detailed architectural design of a building. These plans are abstracted orthographic projections of the structure of each floor onto two dimensions, with symbolic annotations indicating special entities such as doors and windows that are not visible from the top-down orthographic view. These plans are easier to create than the corresponding 3D model of the building because they involve drawing in two dimensions rather than three, and the sheer number of geometric entities drawn is much lower. While these plans may contain small inconsistencies, most can be solved algorithmically in two dimensions.

With the BMG system, input floor plans from AutoCAD are passed through filters that perform topological correction and semantic analysis. Disjoint and overlapping entities are corrected, symbols indicating doors and windows are located, and edges are grouped into contours representing each labeled space on the plan. The result is then extruded to form the correct polyhedral model of the floor. A method is provided for stacking and assembling individual floors, and incorporating other structural elements such as staircases, into a composite building model with correct topology. Results are compatible with the Berkeley WALKTHRU system for interactive visualization of polyhedral environments, and the NIST CFAST fire simulator for buildings. The system was used to generate a new model of the new Soda Hall computer science building at Berkeley, using floor plans drawn by architects.





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