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Josephine Anstey

Building a Low-Cost VR System 

VR Studio, DMS UB

VR on a sheet
First version using a 
bed sheet as a screen.
Basic 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

Components
screen & tracking antenna
  • 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
passive glasses
  • 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.

Result
  • 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
team Team
system as of Aug 2001