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 perfloor 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.

Focus + context visualization facilitates the exploration of complex information spaces. This paper proposes 3D generalization lenses, a new visualization technique for virtual 3D city models that combines different levels of structural abstraction. In an automatic preprocessing step, we derive a generalized representation of a given city model. At runtime, this representation is combined with a full-detail representation within a single view based on one or more 3D lenses of arbitrary shape. Focus areas within lens volumes are shown in full detail while excluding less important details of the surrounding area. Our technique supports simultaneous use of multiple lenses associated with different abstraction levels, can handle overlapping and nested lenses, and provides interactive lens modification.

This paper describes an approach for smart and physically-based navigation, which aims at supporting effective and intuitive user interactions with 3D geovirtual environments (GeoVEs). The approach is based on two aligned concepts: 1) All navigation techniques are controlled by constraints that ensure user orientation and avoid "getting lost" situations. 2) All navigation techniques are handled in a time-coherent way achieving steady, continuous user movements using a physically-based motion model. Based on these concepts, we demonstrate several ways to improve commonly used navigation techniques for geovirtual environments.