Abstract

Architects, urban planners, the film and gaming industry as well as map makers are all very much interested in detailed, semantic city models. While generating a synthetic city has become much easier thanks to procedural modelling, automatically modelling an existing city remains a challenge. With procedural modelling, a building is described as a procedure, wherein an initial shape is successively refined according to a formal grammar set of rules. In this work, we present a set of methods to automatically instantiate and generate such sets of rules, from pictures. First, we present the applications and challenges behind city modelling. Shape grammars have greatly contributed to making city modelling easier. From there, a large spectrum of applications became possible, such as generating realistic large-scale virtual cities or fine-grained urban planning simulations. We introduce the shape grammar framework and explain how it is used to represent buildings. Nevertheless, when it comes to modelling an existing city, much of the work remains a tedious, manual task. The first steps to an automatic pipeline include facade extraction and style detection. Next, we distinguish