Visualization of Real Cities Based on Procedural Modeling

This contribution presents a solution based on a photographs analysis allowing the computation of procedural models of façades. The goal is to extract from a photograph of a façade the main features such as the upper limit of the ground floor, the axis aligned boundary lines between the stories and the windows, and finally the position and size of unit elements of the façade (windows, doors, etc). Our solution carries out a merging of histograms resulting from image analysis algorithms such as edge, background and hough detectors. The result of this analysis is directly exploited to create a procedural model and supply a catalog of backgrounds and unit elements of façades. Thanks to this procedural modeling, a detailed city model can be stream on-demand to visualization clients by progressively transmitting first the background and unit elements textures needed for the current viewpoint, and secondly the corresponding procedural models of visible façades. Finally, visualization process can leveraged shader functionalities such as relief mapping to navigate within a realistic model of city.