Towards Semantic City Models

3D city modeling is a very demanding task. It suffers from the same problems as general bottom-up 3D acquisition processes. Whatever the 3D acquisition system, there are always objects and surfaces that yield meager performance. Often the problems are fundamental and cannot be resolved through more sophisticated bottom-up processing. If however, one knows what kind of objects are to be modeled – e.g. buildings – strong prior knowledge can be invoked. Inverse procedural modeling is a case in point. It yields more compact and more realistic models, yet requires a grammar to be created and then activated for the style at hand. The paper discusses style classification and the (initial) use of more generic architectural guidelines as ways to mitigate the problems with procedural grammars.