next up previous
Next: Experiments Up: paper Previous: State of the Art

Subsections

Development Environment

Software

The Software base is ''Studierstube''. It's a project started on the Vienna University of technology, which tries to build an environment for collaboration in Augmented Reality[11]. It's very flexible. It runs on SGI Irix, Windows NT and is ported to Linux. At the moment three different tracker-types are supported: Ascension Flock of Birds, Polhemus Fasttrack, and Intersense IS-600 / IS-900. As output-devices see through HMD (Virtual IO i-glasses, Sony Glastron) and Virtual Table (a workbench-like device) are possible. For 3D rendering Studierstube is using SGI OpenInventor. To enable multiuser applications a system called distributed OpenInventor[9] is running on top of Inventor.

Studierstube also tries to find a high quality user-interface[10]. It's using Personal Interaction Panel (PIP). PIP is a two-handed interface to control Studierstube[9]. It consists of a small panel (about 20x20 cm) and a pen which can be used as ``3D mouse''. Both of them are separately tracked. But the application can ``replace'' those tools with anything that is needed, by overpainting it in the HMD-display. Most times the pen remains as a ``3D mouse''. And on the panel some 3D GUI-widget like sliders and buttons are placed to control Studierstube.

For tracking Studierstube uses a trackerserver that multicasts the position and orientation of each sensor to all connected hosts. This is not the fastest method, but it's very flexible. The hosts can be separated, and two persons can work on one project at the same time, and can be in different rooms or even cities.

The applications are only shared libraries loaded when needed. This has some advantages. For example it's possible to run several applications simultaneously[7]. And it's possible to have several instances of the same application running. To make this possible, Studierstube has to implement some techniques that are known from operating systems.

If more than one application is running, than there are some equivalents to windows in 2D for 3D needed. Studierstube has also build in something like 3D-windowing - a box-shaped volume. Unlike it's 2D counterpart, one 3D-window can be shared between users to allow collaboration.

Hardware

Figure 4: Hardware setup
\includegraphics{stube.eps}

The tracking-system used is ascension's Flock of Birds. It has 4 sensors. One on the panel, one for the pen, and two for the two HMDs. Each sensor is attached to an electronic unit. The Transmitter is attached to one of these boxes, and one of the boxes is connected via RS232 to a 486-33MHz PC running Linux. The PC multicasts the 6 degrees of freedom from each sensor to the two rendering machines. The rendering machines are SGI O2 workstation. Each workstation delivers the images for one HMD. The HMDs used are IO Display Systems I-glasses. Figure 3-1 shows the complete setup.

The panel is a simple 20x15 cm wood-tray. The pen is a 20 cm long plastic-pipe. It has one button connected to the PC's parallel board. The exact manufacture is not that important. They both should only be light-weight and comfortable to ``wear''.

Flock of Bird uses DC magnetic tracking which is not that badly disturbed by ferro-magnetic objects as AC magnetic tracking is[1]. According to the specifications the tracker measures up to 72 inch (182 cm). It's static position accuracy is 0.02 inch (0.5 mm) with a standard deviation of 0.07 inch (1.8mm). It's Orientation accuracy is 0.1 \ensuremath{} with a standard deviation of 0.5 \ensuremath{}. Both at a distance of 12 inch (30,5 cm).

The IO Display Systems I-glasses work in 3D mode. For 3D each eye needs an extra image. Those two images are transmitted line-interleaved. The display's transparent LCD have 180.000 pixels for 225x266 lines of resolution. The field of view is 30 degrees for each eye.


next up previous
Next: Experiments Up: paper Previous: State of the Art
vogel 2001-03-19