Die Software-Architektur SCA3D: adaptive 3D Visualisierung und Kooperation in offenen Informationsräumen

This work presents the software architecture SCA3D as a flexible framework for distributed 3D visualization which allows an extended view on new concepts for management of complex and protected 3D documents. Digital data have a determining influence on the modern work flow from the first conception phase to the final manufacturing of a product. In most cases the work flow is a distributed process in which multiple users work together in an environment of networked computers. Requirements for distributed work with digital data, which are regarded as digital documents, are the following: First, well-defined interfaces between processing systems are needed to allow cooperation and data exchange. Second, methods for long-term storage in archives, for retrieval and for distribution of digital documents are required which are able to manage huge amounts of complex digital documents. Third, adaptation of multimedia documents during distribution in heterogeneous environments must be supported to control network and local processing load. Digital libraries, understood as open information spaces, offer a suitable framework for describing solutions that fulfill the above requirements. Here the concept of an open information space is used in the context of digital libraries to emphasize two points: First, that digital library services are not restricted to closed groups of users and information servers. Second, that it is important that uniform conditions for access to digital documents are provided throughout an information space and that interfaces to other information spaces can be established. The main focus of the work presented here is the exploration of new methods for distributed processing of 3D documents in open information spaces. Three dimensional scenes, as for example CAD models, are considered to be digital documents containing structure information, geometric content and descriptive metadata. Examples of applications are: distributed development of new products in the automotive industry using digital mock-ups, medical information systems or cooperative learning environments. On the one hand it can be observed that the number of 3D documents exchanged between applications is growing from year to year and that their complexity increases. On the other hand modern working environments are becoming more heterogeneous. The spectrum of systems involved in a work process can range from powerful workstations in a local network to mobile end devices with restricted processing power and connection bandwidth. As a response to this challenge this dissertation presents a software architecture for distributed 3D visualization that supports document features in open distributed environments and provides functionality for management of complexity and security requirements of 3D documents. The status quo of the research on distributed software architectures for 3D visualization is extended by this work in two ways. First, it develops a new approach to supporting hybrid 2D/3D client scenes in distributed and cooperative work processes. Second, it introduces new methods for complexity and security management that allow distribution of the processing load (rendering) and individual control of the network load. In this context a new method is also presented which enables application independent access to distributed 3D documents (document request broker). This work describes the level-of-information approach that was developed to make it possible to adapt transmission rate and local processing load using a performance metric. Finally, a graded rights concept is part of the software architecture. This concept guarantees the protection of document data by controlled dissemination of copies with adapted information content. In practice the results of this work provide new possibilities for digital product development processes which can now use a wide scale of information about the 3D scenes being worked on. This scale ranges from descriptive metadata to the original 3D content of a document. A scenario like a distributed design review in a strongly heterogeneous environment with multiple developers working on complex and protected 3D documents is now supported in a more direct way than by approaches (full replication approach) which have been previously applied.