Stereo Projection System GeoWall |
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The GeoWall is a cost-effective stereoscopic projection system build from off-the-shelf components. The concept was developed by an academic consortium with its roots in the geological sciences community. GeoWalls are used in research work and classroom teaching in many different disciplines. The principle used is identical with that of a stereoscopic IMAX theater. |
A high-end desktop computer with an advanced graphics board creates two images for the left and right eye. These images are fed into two DLP projectors mounted vertically in a special rack. Filters placed in front of the lenses polarize the two images in different orthogonal directions. Both images are projected on a screen that preserves the polarization. The viewer's stereo glasses contain polarizing filters that separate the images for the left and right eye. The virtual environment is presented in stereo and, depending on the size of the screen, may be presented at life-size scale. |
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Since a typical GeoWall does not track the position of the viewer, the illusion of 3D is only perfectly perceived from a specific position in front of the screen. For a more interactive experience, a "leading viewer" position can be implemented by adding a motion tracker to a pair of stereo glasses. This would allow for continuous syncronization of the projected images to the leading viewer's point of view. Like the CAVE, a Geowall operates in "see-through mode", meaning physical objects can be integrated with the projected virtual environment. A wand or joystick is used for navigation. A single Geowall without tracking has been built at the University of Michigan 3D Lab for approximately $10,000. It can easily be built at other locations (including class rooms) and is highly portable. |
Screen |
6' x 8' rear projection |
Projectors |
2 x InFocus LP530 Projectors |
Glasses |
Linear polarized 3D glasses with 45/135 degree gray/gray lenses |
Computer |
P4 2.4GHz, 1GB RAM, Quadro4 900XGL |
Operating System |
WinXP, Linux |
Movie Playback |
Quicktime or MediaPlayer with DivX 5.03 codec, 1024x384 resolution. |
Realtime Software |
ImmersaView, Performer, and many other native OpenGL applications, eg. Quake 3 |
For a single image to be displayed correctly, the left image and the right image are composited into a single larger image (see below). The individual images should be 1024x768 and the composited image should be 2048x768.
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An animated movie is handled in much the same way as a single image. The xeyedmary plugin for 3D Studio Max assists in the creation of series of these dual images which may then be composited into an animation. For realtime display of still models, the VRML format has proved very successful. |
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Classroom |
3d glasses |
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Bull Creek GIS data |
Ambulance |
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Fish |
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More information on the GeoWall is available at the GeoWall Consortium. |
Copyright 2008 ©, the Regents of the University of Michigan, Ann Arbor, Michigan, USA