New acquisition methods have increased the availability of surface property data that capture location-dependent data on feature surfaces. However, these data are not supported as fully in the geovisualization of the Digital City as established data categories such as feature attributes, 2D rasters, or geometry. Consequently, 3D surface properties are largely excluded from the information extraction and knowledge creation process of geovisualization despite their potential for being an effective tool in many such tasks. To overcome this situation, this paper examines the benefits of a better integration into geovisualization systems in terms of two examples and discusses technological foundations for surface property support. The main contribution is the identification of computer graphics techniques as a suitable basis for such support. This way, the processing of surface property data fits well into existing visualization systems. This finding is demonstrated through an interactive prototypic visualization system that extends an existing system with surface property support. While this prototype concentrates on technology and neglects user-related and task-related aspects, the paper includes a discussion on challenges for making surface properties accessible to a wider audience.
This paper presents an approach to real-time rendering of non-planar projections with a single center and straight projection rays. Its goal is to provide the same optimal and consistent image quality GPUs deliver for perspective projections. It therefor renders the result directly without image resampling. In contrast to most object-space approaches, it does not evaluate non-linear functions on the GPU, but approximates the projection itself by a set of perspective projection pieces. Within each piece, graphics hardware can provide optimal image quality. The result is a coherent and crisp rendering. Procedural textures and stylization effects greatly benefit from our method as they usually rely on screen-space operations. The real-time implementation runs entirely on GPU. It replicates input primitives on demand and renders them into all relevant projection pieces. The method is independent of the input mesh density and is not restricted to static meshes. Thus, it is well suited for interactive applications. We demonstrate an analytic and a freely designed projection based on our method.
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