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Using object-oriented databases as the primary data source in VR applications has a variety of advantages, but requires the development of new techniques concerning data modeling, data handling and data transfer from a Virtual Reality system’s point of view. The many advantages are outlined in the first part of this paper. We first introduce versioning and collaboration techniques as our main motivation. These can also be used in the traditional file based approach, but are much more powerful when realized with a database on an object and attribute level. Using an object-oriented approach to data modeling, objects of the real world can be modeled more intuitively by defining appropriate classes with their relevant attributes. Furthermore, databases can function as central communication hubs for consistent multi user interaction. Besides, the use of databases with open interface standards allows to easily cooperate with other applications such as modeling tools and other data generators. The second part of this paper focuses on our approach to seamlessly integrate such databases in Virtual Reality systems. For this we developed an object-oriented internal graph database and linked it to object-oriented external databases for central storage and collaboration. Object classes defined by XML data schemata allow to easily integrate new data models in VR applications at run-time. A fully transparent database layer in the simulation system makes it easy to interchange the external database. We present the basic structure of our simulation graph database, as well as the mechanisms which are used to transparently map data and meta-data from the external database to the simulation database. To show the validity and flexibility of our approach selected applications realized with our simulation system so far e. g. applications based on geoinformation databases such as forest inventory systems and city models, applications in the field of distributed control and simulation of assembly lines or database-driven virtual testbeds applications for automatic map generation in planetary landing missions are introduced.

The development of algorithms providing a close to reality simulation of dynamic virtual worlds made substantial technological progresses during the last decade — contrary to the close to reality simulation of bulk solids. Standard simulation methods like particle or rigid-body simulation are not applicable to this simulation problem because a large number of elements is needed for convincing simulation results which cannot be handled in real-time. In this paper we present a kind of 3-dimensional cellular automaton which can handle a large number of elements at the cost of a spatial discretization. This approach is combined with state of the art rigid body simulation techniques resulting in a close to reality simulation of bulk solids in real-time applications.

Simulation in the context of engineering often focuses on very special details of global systems. Robot designers usually begin with the analysis of new actuators and joint designs. This corresponds to a "bottom-up"-strategy in the development of simulation models. For classical fields of application of robotics, e.g. in production plants with a well defined environment this is the approved method, because it allows very detailed insights into the analyzed subsystems. On the other hand, unpredictable effects of the interaction of multiple subsystems may easily be overseen. In particular, nontechnical environments like in moon exploration tasks or in a biological environment like in forestry applications are hard to describe in an analytical way to integrate them into an analytical simulation model. This is why this paper presents the idea and some practical aspects of the development of "Virtual Testbeds". In a Virtual Testbed, the entire system is simulated as a whole in Virtual Reality -not only small subsystems of a global system. According to the requirements different subsystems are simulated with different levels of detail. In contrast to the classical "bottom-up"-strategy this can be seen as a "topdown"-approach. Therefore the employment of a multi-body dynamics system as a platform for the development of versatile simulation and testing environments is proposed. Using the examples of the evaluation and testing of an extraterrestrial walking exploration robot design and the development of a method for self-localization in forestry, the idea is further deepened. As a special field of attention the integration of a method of soil simulation as a particular requirement of a Virtual Testbed for walking exploration robots is presented.

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