From tom@evl.uic.edu Fri Aug 1 10:54:19 1997 Date: Fri, 1 Aug 1997 08:21:53 -0500 From: tom@evl.uic.edu To: veg@ncsa.uiuc.edu, all@evl.uic.edu Cc: pls@ncsa.uiuc.edu Subject: STUDIERSTUBE STUDIERSTUBE: A NEW TOOL FOR COLLABORATIVE VISUALIZATION 08.01.97 by Alan Beck, editor in chief HPCwire ============================================================================= Funded by the Austrian Science Foundation, the Vienna University of Technology's Institute of Computer Graphics' Studierstube Project seeks to develop an architecture for multi-user augmented reality experiences. Currently, the project's focus is on the visualization of scientific data sets. However, the technology can be applied to a large body of potential applications, including collaborative design, teaching and commercial presentations. To learn more about Studierstube, HPCwire interviewed Dieter Schmalstieg, a member of the research team. --- HPCwire: Please give a general overview of Studierstube and provide a brief history of its development and your role in it. SCHMALSTIEG: "The team working on STUDIERSTUBE is composed of the following researchers -- Michael Gervautz (supervisor), Anton Fuhrmann, Zsolt Szalavari, Helwig Loeffelmann and myself. "The STUDIERSTUBE system allows multiple collaborating users to simultaneously study three-dimensional visualizations in a "study room" -- German: "STUDIERSTUBE" (inspired by the classic play "Faust"). Each participant wears an individually head-tracked see-through HMD (head-mounted device) providing a stereoscopic real-time display. The use of individual displays and head-tracking for each participant allows stereoscopic, undistorted images to be presented to everyone. There are no constraints regarding the viewpoint, e.g., unlike the Workbench, users may sit on opposite sides of the table, which in combination with the see-through property of the HMDs allow users to see each other. This also avoids the fear of bumping into obstacles which often limits the freedom of movement in purely immersive setups. "The HMDs we use -- Virtual I--O i-glasses -- are very lightweight and unobtrusive, but only of limited resolution and small (30 degrees) field of view. Rendering separate images for each user gives great flexibility in the choice of the presented image, but also makes the rendering effort proportional to the number of users, whereas CAVE and (single-user) Workbench require only a constant rendering effort. "The defining features of STUDIERSTUBE are: * Augmented props: We exploit the capabilities of AR to construct a three-dimensional user interface needed for controlling the presentation and possibly the simulation by introducing tracked real-world objects that combine physical items and overlaid computer graphics. * Customized views: In addition to individual choice of viewpoint, customized views of the data are possible, e.g., one user may want to see stream lines added to the basic image, while another may not. Two users in the same room may see different aspects of the same object at the same time. * Usage of space: The space in the STUDIERSTUBE can be used similarly to a CAVE (multiple users standing around), but also allows a workbench setup (users gathering at a blank table with free choice of seating). * Organizational advantages: While the cost of the STUDIERSTUBE's hardware components are certainly higher than a conventional desktop visualization station consisting of only a graphics workstation, they are very conservative compared to a setup like the CAVE. This is particularly important as the potential users of the STUDIERSTUBE -- research groups -- are typically operating on a tight budget. Furthermore, the setup consumes little space and is relatively easy transportable." HPCwire: How would you compare Studierstube with other popular virtual-reality environments, including the Immersadesk and CAVE? What are its strong points and shortcomings? What kind of processing and memory capabilities are required to support it most effectively? SCHMALSTIEG: "STUDIERSTUBE compares quite favorable to established approaches such as Immersadesk and CAVE. It provides a workable alternative, especially if you are operating on a budget. * Cost: While the hardware cost for a CAVE can be described as extremely high, and for an Immersadesk as still very high, a STUDIERSTUBE has moderate cost, that is dominated by the image generator. Yet STUDIERSTUBE manages to deliver most of the advantages of CAVE/Immersadesk at a fraction of the cost. * Space requirements: The projection system for an Immersadesk and especially for a CAVE requires a lot of space, so if space is tight (such as in our lab), such a system is physically impossible. * Number of users with true stereoscopic display: CAVE and Immersadesk are both essentially single-user systems, because only one user wears a head-tracker that determines the viewpoint for the 3-D images. All others experience severe perspective distortions; they have to stand close to the leading user, and the leading user may not move or the other users will get sea-sick. "The new Immersadesk DUO uses interleaving to support two independent head-tracked users, but only at half the frame rate (i.e. 60Hz instead of 120). Half of the time -- when the images for the other user are presented -- the image is blackened; consequently the image appears to flicker. It is obvious that this approach does not scale much beyond two users. On the contrary, STUDIERSTUBE does not suffer from this problem, its limits on scalability are solely defined by the capacity of the image generator to render images for all users fast enough -- throw more graphics hardware at the problem, and the system scales. * Visual quality: The most severe drawback of STUDIERSTUBE is the limited resolution of today's low-cost HMDs. We found that the limited field of view is the most contraining factor (surprisingly it's not the low resolution). Clearly, CRT-based projection such as used in the CAVE scores much higher in that area. However, it is possible to use higher-rez HMDs, but they cost much more. An unexpected benefit of the low resolution is that the pixel load of the image generator is reduced, which allows to use mid-range image generators and keep overall system cost low. "Here is a short hardware "shopping list" for our current STUDIERSTUBE: 
- SGI O2 workstation (image generator)
- SGI Indigo2 Maximum Impact (running AVS)
- Polhemus FasTrak with 4 receivers and a Pentium 75 for signal processing
- 2 sets of Virtual IO I-Glasses
- "Cheapernet" 10BaseT Ethernet
- "PIP" - tracked Pen & Pad, home-grown
- a kitchen table"
HPCwire: Has Studierstube been utilized for solving real-world problems requiring collaborative V-R? Please detail such applications. SCHMALSTIEG: "Our major field of application has been in scientific visualization of dynamical systems. Experts in this field work "next door", so the development of such a collaboration was a logical step. "The scientific visualization researchers had developed a number of visualization projects on dynamical systems. This is a complex area of mathematics, that is very hard to imagine from numbers. The images and animations produced before the collaboration helped to understand important aspects, but they lacked the possibility of interactive exploration. "Our experiences so far with bringing visual representations of the dynamical systems into STUDIERSTUBE and allowing interactive exploration and even some "computational steering" (on-the-fly recomputation of the model with new settings) greatly enhanced the insight into the problem and lead to new and better understanding. STUDIERSTUBE proved to be the perfect user interface for understanding complex mathematical structures, both for collaborating scientists and for tutor/student settings. "Technically, the system was implemented by using the visualization software AVS on a separate machine for computing the 'content', which was rendered on the STUDIERSTUBE SGI machine. A loose coupling between the two processes (Studierstube graphics server and AVS) was realized by network message passing: 3-D models are sent from AVS to STUDIERSTUBE, and control commands input by the user via the PIP. "Another application realized in the Studierstube is a virtual casino where multiple users can play French Roulette on a kitchen table without any physical props. We think that the potential of the Studierstube as the next-generation user interface for video games should be further investigated. Today's video games such as the Nintendo 64 almost have the graphics capability needed for STUDIERSTUBE, and the conservative space requirements of STUDIERSTUBE make it suitable for home usage." HPCwire: How does Studierstube integrate with other projects at the Institute of Computer Graphics? Are there any efforts underway to enhance Studierstube or develop its potential further? SCHMALSTIEG: "As for the integration aspect, there are serveral: - Two-handed Interaction with the Personal Interaction Panel (PIP): We are investigating new methods that make good use of human's capabilities to work in three dimensions. The PIP is a tracked pen/pad combination that allows bimanual operation and is applicable for a surprisingly large variety of tasks. In the STUDIERSTUBE, the PIP is used as a device for handling virtual objects or as a cutting plane. - STUDIERSTUBE being a distributed graphics system benefits from technology developed in the "Remote Rendering Environment" that optimizes distribution of graphical data in distributed virtual environments. ( http://www.cg.tuwien.ac.at/research/vr/remoterender/ ) In particular the SmoothLODS technology is successfully applied in STUDIERSTUBE ( http://www.cg.tuwien.ac.at/research/vr/smoothlods/ ) and the virtual navigation paradigm SEAMS ( http://www.cg.tuwien.ac.at/research/vr/seams/ ) was tested in the STUDIERSTUBE framework. "We are still developing STUDIERSTUBE further. Our goal is a high level rapid prototyping system for STUDIERSTUBE-style collaborative augmented reality applications. Content creators should be able to quickly assemble interaction styles and concentrate on the presentation, not on the technical details. "Other aspects of the research involve testing the concept with more real-life applications and gathering experiences how such an environment can improve work. We would welcome any suggestions to that." HPCwire: How is Studierstube made available to interested users? SCHMALSTIEG: "Our limited funding has not yet allowed us to build more than one prototype, so our current users all had visit our lab to test STUDIERSTUBE. However, we would like to communicate with everyone seriouly interested in STUDIERSTUBE and invite them to contact us. ( http://www.cg.tuwien.ac.at/research/vr/studierstube/ ) -------------------- Alan Beck is editor in chief of HPCwire. 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