Virtual Rear Projection: Technology

1
Virtual Rear Projection Technology Evaluation

• Jay Summet
• summetj_at_cc.gatech.edu

2
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)

3
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

4
Rear Projection

• No shadows!
• But extra costs...
• Display Material
• Installation
• Space cost (77 sq. ft.)
• Immobile

5
Larger Board Higher Cost
6
Front Projection

• Inexpensive
• Display Screen
• Installation
• Mobility
• Effective use of space.
• But shadows blinding light are annoying!

7
Shadows
8
Blinding Light
9
Warped Front Projection (WFP)

• Moves shadow away from directly in front of the
  user.
• Commercial products using WFP
• NEC WT600
• 3M IdeaBoard

10
WFP Measurements
166
3379
11
Passive VRP (PVRP)

• Overlapped projectors fill in shadows.
• Calibration via camera or manually.
• Projective transforms done on graphics card.

12
Passive VRP Measurements
167
2509
13
Movie (part 1)

• Demo Movie of WFP/PVRP

14
Benefits of Redundant Illumination
Two Projectors (PVRP)
One Projector (WFP)
15
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?

16
Projection Technologies Studied
Front Projection
Virtual Rear Projection
Warped Front Projection
Rear Projection
17
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

18
Task

• Box Task
• 8 starting positions
• Target in Center
• Dependent Variables
• Acquire time
• Total Time
• Number of occluded boxes

19
Results (1/3)

• Subjective
• Users found projected light annoying
• Users had clear technology preferencesFP, WFP
  lt VRP lt RP

20
Results (2/3)

• Quantitative
• Box Acquire Time SlowerFP lt WFP, VRP lt RP
• Less Boxes OccludedFP 178 WFP 66 VRP 4 RP
  0

21
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

22
Movie

• Participant Video Figure

23
Edge of Screen (7 participants)
24
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)

25
Move on Occlusion (3 participants)

• These participants would move whenever they
  occluded a box, and stay there until they
  occluded another.

26
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.

27
Projected light is a larger problem as you add
more projectors.
28
Technology Development

• Shadow Elimination CVPR '01
• R. Sukthankar, T.-J. Cham, G. Sukthankar
• U. Kentucky C. Jaynes, Visualization 2001

29
Shadow Elimination Measurements
221
1052
30
Technology Development

• Blinding Light Suppression CVPR '03
• Tat Jen. Cham, Jim Rehg, Rahul Sukthankar,Gita
  Sukthankar

31
SE BLS Measurements
34
1165
32
Interesting, but useless

• Required an unoccluded view of the screen, too
  slow.

33
Technology Development

• Switching PROCAMS '03
• Ramsaroop Sommani
• GPU Enhancements PROCAMS '05
• Matt Flagg

34
Active Virtual Rear Projection

• Detects occluders, turns off pixels they are
  occluding, and fills in those pixels with
  alternate projectors

35
Active VRP Measurements
12
1466
36
Movie (part 2)

• Active VRP

37
Future Work

• User evaluation of Active VRP
• Controlled laboratory study (80 participants)
• Exploratory Research
• AeroSpace Engineering Design Lab
• Home-Office in Aware Home

38

• More information
• summetj_at_cc.gatech.edu
• http//www.cc.gatech.edu/cpl/vrp
• http//www.cc.gatech.edu/cpl/procams

39
Thank you!

• The End

40
Table of Relative Performance