Single image and topology approaches for modeling buildings.

The paper presents a method and strategy for building reconstruction and visualization from single images and topologic approaches. In our method, geometric and semantic data of entities to be modeled are extracted. The structuring of geometric, topologic and semantic data is done within the measuring process. In most applications, the model contains only information about the shape and the texture of the object while its topologic and semantic data are not processed. We combine this information to reconstruct outdoor and indoor scenes. Single image techniques based on projective geometry aspects as vanishing points and homography are adopted. This configuration was preferred to the traditional stereoscopic and multi-image techniques considering the particularity of the environment to be modeled and application difficulties of these techniques. Indoor scenes are structured in blocks like rooms, corridors, etc. with their own orthogonal coordinate systems. A block is presented in an abstract way using a Data Conceptual Model to identify the entities and the relations to include in the database. The 3D model can then be reconstructed automatically from the information stored in the database. Coplanarity conditions between entities as windows or doors and the compatible walls are taken into account. The outdoor and indoor blocks are merged by the use of “virtual doors” (or windows). These doors are defined in function of the wall thickness and the translation direction according to the local coordinate systems of the blocks. The final model offers several applications: - topologic navigation in the model, - visualization and extraction of the geometric characteristics of given types of entity (areas, perimeters, etc.), - visualization of " virtual doors ", used to calculate the parameters of the transformation (rotation and translation) between the reference coordinate system and the local systems attached to the different blocks, - generation of photo-realistic models As examples, the method has been applied to the modeling of the exterior part of the old Zurich city hall (CIPA dataset from 1999) and to the modeling of a part of the ENSAIS buildings