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