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We present a non-photorealistic rendering technique to transform color images and videos into painterly abstractions. It is based on a generalization of the Kuwahara filter that is adapted to the local shape of features, derived from the smoothed structure tensor. Contrary to conventional edge-preserving filters, our filter generates a painting-like flattening effect along the local feature directions while preserving shape boundaries. As opposed to conventional painting algorithms, it produces temporally coherent video abstraction without extra processing. The GPU implementation of our method processes video in real-time. The results have the clearness of cartoon illustrations but also exhibit directional information as found in oil paintings.

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A BFigure 1: Exemplary result of the visualization system that enables the seamless transition between abstract graphics (A) and a photorealistic version (B) view-dependently. The sequence below shows single frames of this transition. AbstractVirtual 3D city models play an important role in the communication of complex geospatial information in a growing number of applications, such as urban planning, navigation, tourist information, and disaster management. In general, homogeneous graphic styles are used for visualization. For instance, photorealism is suitable for detailed presentations, and non-photorealism or abstract stylization is used to facilitate guidance of a viewer's gaze to prioritized information. However, to adapt visualization to different contexts and contents and to support saliencyguided visualization based on user interaction or dynamically changing thematic information, a combination of different graphic styles is necessary. Design and implementation of such combined graphic styles pose a number of challenges, specifically from the perspective of real-time 3D visualization. In this paper, the authors present a concept and an implementation of a system that enables different presentation styles, their seamless integration within a single view, and parametrized transitions between them, which are defined according to tasks, camera view, and image resolution. The paper outlines potential usage scenarios and application fields together with a performance evaluation of the implementation.

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.

Indoor routing represents an essential feature required by applications and systems that provide spatial information about complex sites, buildings and infrastructures such as in the case of visitor guidance for trade fairs and customer navigation at airports or train stations. Apart from up-todate, precise 3D spatial models these systems and applications need user interfaces as core system components that allow users to efficiently express navigation goals and to effectively visualize routing information. For interoperable and flexible indoor routing systems, common specifications and standards for indoor structures, objects, and relationships are needed as well as for metadata such as data quality and certainty. In this paper, we introduce a classification of indoor objects and structures taking into account geometry, semantics, and appearance, and propose a level-of-detail model for them that supports the generation of effective indoor route visualization.

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