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3D geovirtual environments (3D GeoVEs) such as virtual 3D city models serve as integration platforms for complex geospatial information and facilitate effective use and communication of that information. Recent developments towards standards and service-based, interactive 3D geovisualization systems enable the large-scale distribution of 3D GeoVEs also by thin client applications that work on mobile devices or in web browsers. To construct such systems, 3D portrayal services can be used as building blocks for service-based rendering. Service-based approaches for 3D user interaction, however, have not been formalized and specified to a similar degree. In this paper, we present a concept for service-based 3D camera control as a key element of 3D user interaction used to explore and manipulate 3D GeoVEs and their objects. It is based on the decomposition of 3D user interaction functionality into a set of services that can be flexibly combined to build automated, assisting, and application-specific 3D user interaction tools, which fit into service-oriented architectures of GIS and SDI based IT solutions. We discuss 3D camera techniques as well as categories of 3D camera tasks and derive a collection of general-purpose 3D interaction services. We also explain how to efficiently compose these services and discuss their impact on the architecture of service-based visualization systems. Furthermore, we outline an example of a distributed 3D geovisualization system that shows how the concept can be applied to applications based on virtual 3D city models. |
