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Introduction
Jay Summet - PhD student, Georgia Institute of Technology
Co-Advised: Gregory Abowd (HCI / Ubicomp) & Jim Rehg (Computer Vision)
Other work:
– Tracking and Projecting on handheld displays (Pervasive2005, UIST 2005),
– Detecting camera phones and blinding them (Ubicomp 2005)
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Virtual Rear Projection Using multiple redundant front projectors to
emulate the experience of a rear projected
surface.
• Introduction
• Motivation for VRP
• Initial Technology Development
•User Evaluation• More Technology Development
• Future Work
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Rear Projection
• No shadows!
• But extra costs...– Display Material
– Installation
– Space cost (77$ sq. ft.)
– Immobile
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Larger Board = Higher Cost
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Front Projection
• Inexpensive:– Display Screen
– Installation
– Mobility
• Effective use of space.
• But shadows & blinding light are annoying!
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Shadows
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Blinding Light
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Warped Front Projection (WFP)
• Moves shadow away from directly in front of the user.
• Commercial products using WFP:
– NEC WT600
– 3M IdeaBoard
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WFP Measurements
3379 166
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Passive VRP (PVRP)
• Overlapped projectors fill in shadows.
• Calibration via camera or manually.
• Projective transforms done on graphics card.
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Passive VRP Measurements
2509 167
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Movie (part 1)
Demo Movie of WFP/PVRP
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Benefits of Redundant Illumination
One Projector (WFP) Two Projectors (PVRP)
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Research Questions
•Are shadows / blinding light a problem?– Very little research with interactive
surfaces performed using front projection.
– But no real research into the effects of shadows on users of interactive surfaces.
• Is Passive VRP “good enough”?
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Projection Technologies Studied
Front Projection Virtual Rear Projection
Warped Front Projection Rear Projection
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Participants
17 Participants– Undergraduate students
– Mean age: 21.3 Std. Dev 1.77
– 9 males, 8 females
– Exclusively right handed
– Normal or corrected-to-normal vision
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Task
Box Task– 8 starting positions
– Target in Center
Dependent Variables– Acquire time
– Total Time
– Number of occluded boxes
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Results (1/3)
Subjective:– Users found projected light annoying
– Users had clear technology preferences:FP, WFP < VRP < RP
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Results (2/3)
Quantitative:– Box Acquire Time Slower:
FP < WFP, VRP < RP
– Less Boxes OccludedFP – 178 WFP – 66 VRP – 4 RP – 0
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Results (3/3)
Behavioral:– Users adopted coping behaviors to deal with
shadows in the FP and WFP conditions
– Not present in the VRP and RP conditions
• Edge of Screen – 7
• Near Center – 7
• Move on Occlusion – 3
• Dead Reckoning - 1
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Movie
Participant Video Figure
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Edge of Screen (7 participants)
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Near Center (7 participants)
Participants would stand in the center and...– ...either be short enough so that they would
not occlude boxes. (3 participants)
– ...or they would sway their bodies to find occluded boxes. (4 participants)
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Move on Occlusion (3 participants)
These participants would move whenever they occluded a box, and stay there until they occluded another.
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Findings (CHI 05)
• Users prefer Rear Projected and Passive Virtual Rear Projected displays over the others.
• RP and passive VRP eliminated coping behaviors seen in FP and WFP.
• Users find projected light to be annoying.
• Passive VRP casts light on users.
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Projected light is a larger problem as you add more projectors.
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Technology DevelopmentShadow Elimination – CVPR '01
– R. Sukthankar, T.-J. Cham, G. Sukthankar
– U. Kentucky – C. Jaynes, Visualization 2001
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Shadow Elimination Measurements
1052 221
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Technology DevelopmentBlinding Light Suppression – CVPR '03
– Tat Jen. Cham, Jim Rehg, Rahul Sukthankar,Gita Sukthankar
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SE + BLS Measurements
1165 34
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Interesting, but useless
•Required an unoccluded view of the screen, too slow.
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Technology Development
Switching – PROCAMS '03
– Ramsaroop Sommani
GPU Enhancements – PROCAMS '05
– Matt Flagg
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Active Virtual Rear Projection
• Detects occluders, turns off pixels they are occluding, and fills in those pixels with alternate projectors
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Active VRP Measurements
1466 12
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Movie (part 2)
Active VRP
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Future Work
User evaluation of Active VRP– Controlled laboratory study (80 participants)
– Exploratory Research
• AeroSpace Engineering Design Lab
• “Home-Office” in Aware Home
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More information:[email protected]
http://www.cc.gatech.edu/cpl/vrphttp://www.cc.gatech.edu/cpl/
procams
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Thank you!
The End
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Table of Relative Performance