3D Interaction Techniques in Multi User Virtual Reality : towards scalable templates and implementation patterns for cooperative interfaces Multi user projection systems provide a coherent 3D interaction space for multiple co located users that facilitates mutual awareness full body interaction and the coordination of activities. The users perceive the shared scene from their respective viewpoints and can directly interact with the 3D content. This thesis reports on novel interaction patterns for collaborative 3D interaction for local and distributed user groups based on such multi user projection environments. A particular focus of our developments lies in the provision of multiple independent interaction territories in our workspaces and their tight integration into collaborative workflows. The motivation for such multi focus workspaces is grounded in research on social cooperation patterns specifically in the requirement for supporting phases of loose and tight collaboration and the emergence of dedicated working territories for private usage and public exchange. We realized independent interaction territories in the form of handheld virtual viewing windows and multiple co located hardware displays in a joint workspace. They provide independent views of a shared virtual environment and serve as access points for the exploration and manipulation of the 3D content. Their tight integration into our workspace supports fluent transitions between individual work and joint user engagement. The different affordances of various displays in an exemplary workspace consisting of a large 3D wall a 3D tabletop and handheld virtual viewing windows promote different usage scenarios for instance for views from an egocentric perspective miniature scene representations close up views or storage and transfer areas. This work shows that this versatile workspace can make the cooperation of multiple people in joint tasks more effective e.g. by parallelizing activities distributing subtasks and providing mutual support. ...