THE “WEDGE”
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Transcript of THE “WEDGE”
THE “WEDGE”Rod Boswell, Peter Alexander
Plasma Research Laboratory,
Research School of Physical Sciences and Engineering,
Henry Gardner, Dave, Hugh, Rhys, Pascal
Department of Computer Science, FEIT,
and ANU Supercomputer Facility,
Australian National University
http://wedge.anu.edu.au/
Limits of Vision of a human eye• Total 15M pixels over the FOV of 4/3 (4) steradians, most dense in fovea.
• Pixel resolution
• 28 seconds of arc - highest resolution
• 50 seconds of arc - "20/20" vision
• 1.5 arc - minutes - "20/30" acceptable vision
• Normal 18" desktop computer at 24" and 1280 x 1024 resolution is at limit of resolution.
• Small 48 cm. TV at 3 metres and 200 lines resolution can be improved by about a factor of two (eg. SVHS or Digital).
• Each screen has resolution 1280 x 1024, image area 1.5 x 1.25 metres and viewed from about 1.5 metres yields a FOV of 0.8 steradians per screen.
• Stand in 4th corner of WEDGE and the corners make 90 degrees, ie. about that of stereo vision, yielding a FOV of /2 ie. about 1.6 steradians. The display limit is about 20% of the eye limit.
Depth Clues from real world
• 1. Occlusion
• 2. Perspective projection
• 3. Binocular disparity
• 4. Motion Parallax
• 5. Convergence
• 6. Accommodation
• 7. Atmospheric
• 8. Lighting and Shadow
• Workstation 1, 2, 7, 8 "VR" adds 3, 4 and 5
Virtual Reality (“virtual environments”)
• 3D (perspective) computer graphics in stereo• Interactivity
– Mouse
– 6D Mouse
– “Head tracking”
– Robotic arms......
• Human Computer Interface research (HCI)• High end: Silicon Graphics; supercomputing• Games end: PC cards; helmets; fun parlours
The first Wedge
The big wigs get their day
Rod receives the WORD from Henry
Wedgeorama
The p-Wedge at Wagga-Wagga (outreach)
“Immersive” projection-based VR
• Headsets are cumbersome and “daggy”?– complaints of motion sickness
– solitary enjoyment?
• The CAVETM
– Small “room” with back (and down) projected stereo images
– “Immersive”; viewers are surrounded by the images
– Collaborative
– 6D mouse; head-tracking; maybe audio...
– Fraternal; user group interaction
– Expensive
Barriers to the diffusion of VR technology
• Expensive• Applications not fully developed• HCI: Visual overload can cause discomfort
The Wedge• Built from “the bottom up” (including software)• Sacrifice interactivity for affordability• Driven by a particular application• Driven by a particular idea• First immersive “VR theatre” in Australia
The Wedge is...
• Two screens (“standard rearlight”) back-projected in stereo
• Frame made of extruded aluminium flush with the floor
• Two CRT projectors– NEC Multisync XG75
– 800 x 600 non-interlaced images at 120 Hz (60Hz each eye)
• Intergraph TDZ2000• Shutter glasses and emitters • Ultrasonic head-tracker with 6D mouse (Logitech)
Intergraph TDZ2000
• Dual 300 MHz Pentium II• 128 MB RAM• 64 MB texture memory• 32 MB frame buffer• two VX25 graphics boards with frame
synchronisation at 120 Hz (two raster accelerators and one geometry accelerator)
• resolution up to 1824x1386 pixels• 1.6 M Gourad shaded triangles per second
Head-tracker
• Logitech (Fakespace)• 23 kHz• Three loudspeakers and three microphones
mounted in plastic equilateral triangles (of length 25 cm and 5cm respectively)
• Range over 1.5m; cone shaped volume; angle of 100 degrees
• Resolution of 100 micrometers in position and 0.1 degrees in orientation
• Tracking speed up to 75cm/s; rate of 50Hz• Also 6D mouse
Driving idea...
• The corner region of the Wedge appears to offer a greater sense of presence than a single screen
• Depth cue associated with the recession of the screens into the distance
• Anecdotal evidence based on the experience of thousands of observers (Wedgeophiles)
• Images ‘in front of screen’ more compelling than images ‘behind the screen’
Driving Application
• Plasma Fusion experiment at ANU: the H-1 Heliac national facility
• Interactive engineering in a complicated and crowded geometry
• Understanding and communication of physics results
• Remote stereo video with lip synch audio for teaching and the virtual university
Preliminary applications and performance
• Simple molecules (C60 - “bucky-ball”) with vibrational motion
• Mathematical minimum energy surfaces: points, wireframe and solid
• Percolation simulations • Presently limited to 10-20,000 polygons @ 10
Hertz; increased this by a factor of 4 in 1999 and with the new Wedge in ANU Comp Sci a factor of 10 or more.
Image Quality• Resolution, matching, synchronisation all good• Ghosting occasionally distracting
– Light extinction efficiency and spectral bias of the shutter glasses
– Decay time of the phosphor tubes in projectors
• Perception of ghosts also depends on– Horizontal scan rate
– Colour palette
– Movement (animation)
– Suggestion
• Ghosts are usually tinged green
Shutter Glasses
• Synchronised to left/right eye images by infrared signals
• Use crossed polarising filters; finite extinction efficiency
• We have examined two types of shutter glasses – “industry standard” (about US$600 a pair)
– “home entertainment” (about US$30)
• needed to be modified electronically
– both have about 20% extinction!
– closed shutter glasses have a bias towards green
0
0.5
1
1.5
200 300 400 500 600 700 800 900
Normalised Response of Shutterglasses
Wavelength (nm)
GREEN
Projectors
• Measurements of phosphor decay times were carried out using a photodiode and oscilloscope
• Green (3ms half width) is about 1.5 times longer than red (2ms)
• Blue is very fast• Phase varies through the image (due to finite
horizontal scan rate• Problems getting CRT projectors as DLPs
(Victorian Branch) are taking over
1
10
100
0 2 4 6 8 10
Electrohome Phosphor
E.H. Green (standard) E.H. Green (short persistence)E.H. RedE.H. Experimental (P43)NEC GreenNEC Red
Light intensity (arb units)
Time (ms)
Conclusions
• Wedge is a simple and effective VR system• Very popular with the general public• Simple JAVA 3D operating system• More application developments coming• Total equipment cost about US$60k • Ideal for remote teaching
Virtual Language
The field is deeply rooted
in cross disciplinary research.
We intend to thrust
into this virgin soil
and break down conceptual barriers
to plant the seed of new ideas.
WEDGE Language
The Wedge was conceived to envelop the user
who is drawn into the virtual environment
which gives birth to new concepts
and nurtures the growth of new ideas.