Building a Low-Cost VR System 

• It is a projection-based system based on the CAVE and Idesk technology developed at EVL.
• It is a passive-stereo system, with one 7' x 5' screen, and a tracking system.
• A linux PC with a dual headed video card runs the graphics

• Ascension 6 degrees of freedom SpacePad tracker with 3 sensors
• the tracking antenna hangs above & in front of the screen
• it sends out a pine cone shaped magnetic pulse
• tracking sensors send back info on their position & orientation within the tracking signal to a PC kindly donated by UB's CCR
• the Tracking PC is connected by ethernet to the Graphics PC
• Stewart Filmscreen "Disney Black" polarization-preserving rear-projection screen 
• a polarizing preserving screen means that we can do passive stereo
• the screen size of 5 foot * 7 foot was partially determined by the size of our tracking signal, and partially by the size of the room and throw distance of the projectors

• Penguin Computing dual-processor Linux PC for Graphics
• we chose linux because we wanted to use graphics software developed for sgi systems which we can run on linux, specifically Iris Performer and "XP" & "Ygdrasil" VR authoring systems that use Performer developed by Dave Pape
• we also use CAVElib which is available for unix, linux and windows
• Matrox G450 dual-head graphics card
• dual head for 2 channels of video 
• the second component of our passive system
• The Penguin is clearly much cheaper than an SGI onyx. PC's can now draw polygons and textures at a competitive rate, but we see very nasty aliasing with our current video card

• Two Sharp LCD projectors
• simulataneously projecting images for left and right eye 
• a lens shift feature makes it easier to align the 2 images exactly on the screen
• Circular Polarizing Filters (American Polarizer)
• a filter on each projector polarizes the video projection
• the projection passes through the polarizing preserving screen

• Circular Polarizing Glasses (FakeSpace Systems)
• user wears glasses so that the right eye receives the right eye image, the left eye receives the left eye image & the brain fuses the two images for a 3D effect
• Circular polarization is important so that the user does not lose stereo if they tilt their head
• Passive stereo glasses are much cheaper than active glasses. The active glasses are also fragile. This picture shows plastic glasses - cardboard ones are available and even cheaper.

• A rear-projected, 1 wall, passive-stereo VR display device with tracking for a total cost of ~$20,000
• For use in graduate and undergraduate education and the development of virtual reality art works at UB

• Media Study/ Buffalo
• Josephine Anstey
• Chris Galbraith
• Dan Neveu
• Paul Costa
• Dave Pape - VR consultant
• With assistance from the Electronic Visualization Laboratory (EVL) , UIC