1 Virtual Rear Projection: Technology & Evaluation Jay Summet

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

11 Passive VRP (PVRP) Overlapped projectors fill in shadows. Calibration via camera or manually. Projective transforms done on graphics card.

12 Passive VRP Measurements

13 Movie (part 1) Demo Movie of WFP/PVRP

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

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 ProjectionVirtual Rear Projection Warped Front ProjectionRear 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 preferences: FP, WFP < VRP < RP

20 Results (2/3) Quantitative: –Box Acquire Time Slower: FP < WFP, VRP < RP –Less Boxes Occluded FP – 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

30 Technology Development Blinding Light Suppression – CVPR '03 – Tat Jen. Cham, Jim Rehg, Rahul Sukthankar,Gita Sukthankar

31 SE + BLS Measurements

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

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: ams

39 Thank you! The End

40 Table of Relative Performance