Continuous level-of-detail modeling of buildings in 3D city models

This paper introduces a concept for representing and modeling buildings in GIS at continuous levels of quality. Buildings are essential objects of virtual 3D city models, which serve as platforms for integrated, urban geoinformation. Existing concepts for the representation of buildings are restricted to a specific level-of-quality such as block models, roof-including models, architectural models, and indoor virtual reality models. The continuous level-of-quality approach unifies the representation of heterogeneous sets of buildings, which occur in most virtual 3D city models. It also leads to a systematic method for the incremental refinement of buildings - an important requirement of the long-term management of virtual city models. In our concept, a building's geometry is structured on a per-floor basis; each floor refers to a floor prototype, which is defined by a ground plan, walls, and wall segments. To specify the appearance projective textures across floors and textures per wall segment are supported. Application-specific data can be associated similar to appearance information. These few components already allow us to express efficiently most common building features. Furthermore, the approach seamlessly integrates into CityGML, an upcoming standard for virtual city model data.