We describe a view-management component for interactive 3D user interfaces. By view management, we mean maintaining visual constraints on the projections of objects on the view plane, such as locating related objects near each other, or preventing objects from occluding each other. Our view-management component accomplishes this by modifying selected object properties, including position, size, and transparency, which are tagged to indicate their constraints. For example, some objects may have geometric properties that are determined entirely by a physical simulation and which cannot be modified, while other objects may be annotations whose position and size are flexible. We introduce algorithms that use upright rectangular extents to represent on the view plane a dynamic and efficient approximation of the occupied space containing the projections of visible portions of 3D objects, as well as the unoccupied space in which objects can be placed to

Our starting point for developing the Studierstube system was the belief that augmented reality, the less obtrusive cousin of virtual reality, has a better chance of becoming a viable user interface for applications requiring manipulation of complex three-dimensiona information as a daily routine. In essence, we are searching for a 3-D user interface metaphor as powerful as the desktop metaphor for 2-D. At the heart of the Studierstube system, collaborative augmented reality is used to embed computer-generated images into the real work environment In the #rst part of this paper, we review the user interface of the initial Studierstube system, in particular the implementation of collaborative augmented reality , and the Personal Interaction Panel, a two-handed interface for interaction with the system. In the second part, an extended Studierstube system based on a heterogeneous distributed architecture is presented. This system allows the user to combine multiple approaches--- augmented reality, projection displays, and ubiquitous computing---to the interface as needed. The environment is controlled by the Personal Interaction Panel, a twohanded, pen-and-pad interface that has versatile uses for interacting with the virtual environment. Studierstube also borrows elements from the desktop, such as multitasking and multi-windowing. The resulting software architecture is a user interface management system for complex augmented reality applications. The presentation is complemented by selected application examples 1

Studierstube is an experimental user interface system, which uses collaborative augmented reality to incorporate true 3D interaction into a productivity environment. This concept is extended to bridge multiple user interface dimensions by including multiple users, multiple host platforms, multiple display types, multiple concurrent applications, and a multi-context (i. e., 3D document) interface into a heterogeneous distributed environment. With this architecture, we can explore the user interface design space between pure augmented reality and the popular ubiquitous computing paradigm. We report on our design philosophy centered around the notion of contexts and locales, as well as the underlying software and hardware architecture. Contexts encapsulate a live application together with 3D (visual) and other data, while locales are used to organize geometric reference systems. By separating geometric relationships (locales) from semantic relationships (contexts), we achieve a great amou...

The combination of mobile computing and collaborative Augmented Reality into a single system makes the power of computer enhanced interaction and communication in the real world accessible anytime and everywhere. This paper describes our work to build a mobile collaborative Augmented Reality system that supports true stereoscopic 3D graphics, a pen and pad interface and direct interaction with virtual objects. The system is assembled from offthe -shelf hardware components and serves as a basic test bed for user interface experiments related to computer supported collaborative work in Augmented Reality. A mobile platform implementing the described features and collaboration between mobile and stationary users are demonstrated.

This paper focuses on the distributed architecture of the collaborative augmented reality system Studierstube. The system allows multiple users to experience a shared 3D workspace populated by multiple applications using seethrough head mounted displays or other presentation media such as projection systems. The system design is based on a distributed shared scene graph that alleviates the application programmer from explicitly considering distribution, and avoids a separation of graphical and application data. The idea of unifying all system data in the scene graph is taken to its logical consequence by implementing application instances as nodes in the scene graph. Through the distributed shared scene graph mechanism, consistency of scene graph replicas and the contained application nodes is assured. Multi-user 3D widgets allow concurrent interaction with minimal coordination effort from the application. Special interest is paid to migration of application nodes from host to host allowing dynamic workgroup management, such as load balancing, late joining and early exit of hosts, and some forms of ubiquitous computing.

In this paper we present a distributed scene graph architecture for use in the blue-c, a novel collaborative immersive virtual environment. We extend the widely used OpenGL Performer toolkit to provide a distributed scene graph maintaining full synchronization down to vertex and texel level. We propose a synchronization scheme including customizable, relaxed locking mechanisms. We demonstrate the functionality of our toolkit with two prototype applications in our high-performance virtual reality and visual simulation environment.

We describe the Scene-Graph-As-Bus technique (SGAB), the first step in a staircase of solutions for sharing software components for virtual environments. The goals of SGAB are to allow, with minimal effort, independentlydesigned applications to share component functionality; and for multiple users to share applications designed for single users.This paper reports on the SGAB design for transparently conjoining different applications by unifying the state information contained in their scene graphs. SGAB monitors and maps changes in the local scene graph of one application to a neutral scene graph representation (NSG), distributes the NSG changes over the network to remote peer applications, and then maps the NSG changes to the local scene graph of the remote application. The fundamental contribution of SGAB is that both the local and remote applications can be completely unaware of each other; that is, both applications can interoperate without code or binary modification despi...

In this thesis, the design of APRIL, an XML-based language to create content-rich Augmented Reality (AR) applications and interactive presentations, is presented. The state of the art of hardware and software for AR systems is analyzed, to deduce the key concepts and features of APRIL. One central feature of APRIL is the separation of an application's content from the description of the hardware configuration the application should run on. This will allow users to run the same application with different hardware configurations, either reflecting different target platforms, or to replace the original target platform by a simulation environment in the development and testing phase. While the question of content creation...

This paper focuses on the distributed architecture of the collaborative three-dimensional user interface management system Studierstube. The system allows multiple users to experience a shared 3D workspace populated by multiple applications using see-through head mounted displays or other presentation media such as projection systems. The system design is based on a distributed shared scene graph that alleviates the application programmer from explicitly considering distribution, and avoids a separation of graphical and application data. The idea of unifying all system data in the scene graph is taken to its logical consequence by implementing application instances as nodes in the scene graph. Through the distributed shared scene graph mechanism, consistency of scene graph replicas and the contained application nodes is assured. Multi-user 3D widgets allow concurrent interaction with minimal coordination effort from the application. Special interest is paid to migration of application nodes from host to host allowing dynamic workgroup management, load balancing, ad-hoc collaboration, and ubiquitous computing.

D applications, but with the focus lying on support for multi-processor and multi-pipeline systems, for distributed applications and for advanced rendering effects. Contrary to these developments, this work focusses on the expressiveness of the scene graph structure as a central tool for developing 3D user interfaces. We present the idea of a context for the traversal of a scene graph which allows to parameterize a scene graph and reuse it for different purposes. Such context sensitive scene graphs improve the inherent flexibility of a scene graph acting as a template with parameters bound during traversal. An implementation of this concept using an industry standard scene graph library is described and its use in a set of applications from the area of mobile augmented reality is demonstrated.