Building%20Stereo%20Tiled%20Display%20Walls%20using%20Linux

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Building Stereo Tiled Display Walls using Linux

• Ray Gasser, rayg_at_bu.edu
• Graphics Programmer/Analyst
• Scientific Computing and Visualization Group
• Boston University

2
Introduction

• Agenda
• Why Linux/Display Wall?
• BU Deep Vision Display Wall
• Stereo (Active vs. Passive)
• Hardware
• Software
• Implementation Issues
• Maintenance Issues
• Resources
• Current Projects
• Conclusions

3
Why Linux/Display Wall?

• Fakespace ImmersaDesk R2
• Screen rigid 6'w x 4'h
• Projection System 1 8" CRT w stereoscopic
  enhancement
• Resolution (fixed) 1280 x 1024 _at_ 120 Hz (1600 x
  1200 opt)
• Lumens 250
• Footprint 6.4'w x 7'd x 7.5'h
• Stereo Active
• Cost 139,000 (includes Ascension space pad
  with wandhead
• and 5 pair shutter glasses)
• http//www.fakespacesystems.com/workdesk1.shtml

4
Why Linux/Display Wall?

• Boston University Deep Vision Display Wall v1.0
• Screen flexible 10'w x 7'h
• Projection System 8 LCD commodity XGA
  projectors
• Resolution (scalable) 2048 x 1536 aggregate
  stereo _at_ 75 Hz
• Lumens 2000 (2 overlapping projectors 2000
  lumens each per tile)
• Footprint 10.5'w x 12'd x 7.5'h
• Stereo Passive
• Cost 50,000 (of which 40k is for the 8
  projectors)
• (80k for everything including Linux
  cluster)
• http//scv.bu.edu/Wall

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Why Linux/Display Wall?
IDesk DVDW
Screen rigid 6w x 4h flexible 10w x 7
Projection 1 8 CRT 8 LCD
Resolution 1280 x 1024 2048 x 1536
Lumens 250 2000
Footprint 6.4w 7d 7.5h 10.5w 12d 7.5h
Stereo Active 120Hz/2 Passive 75Hz
Cost 139,000 50,000
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Why Linux/Display Wall?

• Large Format Display
• High Resolution / Scalable Resolution
• Scalable graphics performance (rendering cluster)
• Multiple displays within wall
• Bright
• Low cost / Scalable cost

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BU Deep Vision Display Wall

• v1.0 (first public showing SC2001 Nov 10-16,
  2001)
• 10'w x 7.5'h rear projected display screen
• 2x2 stereo array (8 LCD XGA projectors)
• 2048x1536 aggregate stereo screen resolution
• 4 Linux render nodes one control/application
  node
• each render node drives 2 projectors
• Passive stereo using linear polarizing
  glasses/filters
• Fast Ethernet interconnect
• http//scv.bu.edu/Wall

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BU Deep Vision Display Wall
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BU Deep Vision Display Wall

• v2.0 (under construction)
• 15'w x 8'h rear projected display screen
• 4x3 stereo array (24 LCD XGA projectors)
• 4096x2304 aggregate stereo screen resolution
• 24 Linux render nodes 1 control node
• each render node drives 1 projector
• 52 Linux compute nodes
• Passive stereo using linear polarizing
  glasses/filters
• Myrinet interconnect

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Stereo (active vs. passive)

• Active Stereo
• Pros
• only one projector per tile (easier alignment)
• no special screen material needed
• Cons
• expensive
• shutter glasses
• high refresh CRT projectors
• requires quad buffer support on video
  card/drivers
• requires framelock/genlock (hardware or software)
• possible eye strain (splitting refresh rate
  between eyes)

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Stereo (active vs. passive)

• Passive Stereo
• Pros
• inexpensive
• polarizing filters
• polarizing glasses
• LCD/DLP projectors
• glasses robust
• don't need Quad buffers
• don't need framelock/genlock
• less eye strain (full refresh rate for each eye)
• Cons
• two projectors per tile
• alignment issues
• space issues
• need special non-depolarizing screen

12
Passive Stereo

• Linear Polarizing Filters
• Pros
• inexpensive
• more light
• Cons
• limited head movement (cross talk)
• ok for walls, bad for CAVEs
• Circular Polarizing Filters (linear wave
  retarder)
• Pros
• unlimited head movement (still need head
  tracking)
• Cons
• more expensive
• less light

13
Hardware Screen

• front vs. rear projection
• non depolarizing for passive stereo
• rigid vs. flexible
• Fresnel/Lenticular
• transmission properties
• http//www.evl.uic.edu/pape/papers/lowcost.spie02/
  node5.html
• viewing angle
• Gain
• mounting hardware
• portability

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Hardware Projectors

• LCD vs. DLP vs. CRT
• Image Quality
• Color
• calibration
• convergence
• uniformity
• gamut
• Resolution
• Inputs
• DVI
• VGA
• svideo
• Polarization Issues

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Hardware Projectors

• Brightness
• Controls
• interface
• tethered remote
• serial
• tcp/ip
• documentation of control codes
• calibration and configuration
• accuracy
• Stability (zoom, focus)
• Refresh Rate
• Weight
• Size

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Hardware Projectors

• Bulbs
• life-time
• greatest maintenance expense
• warranty
• color
• Advanced Features
• lens shifting
• image warping
• frame buffer access
• microprocessor access
• stacking

17
Hardware Video Cards

• Display Channels
• number
• DVI vs. VGA
• Framelock/Genlock
• Quad buffers (active stereo)
• Fully accelerated OpenGL
• Linux driver support

18
Hardware PC Clusters

• Render
• Compute
• Control
• Processors
• 32 bit (Intel XEON, Intel Pentium4, AMD Athlon)
• 64 bit coming (Intel Itanium2, AMD Opteron)
• Cache L1, L2
• number (realtime needs 2)

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Hardware PC Clusters

• I/O
• AGP 3.0 bus (2x/4x/8x) 2.1 GB/s bandwidth
• ATA/100, Ultra 160 SCSI, Ultra 320 SCSI
• System Bus 133MHz, 400MHz
• Memory
• DDR SDRAM
• RDRAM (dual-channel)
• Kernel supports up to 64GB of physical memory

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Hardware Network/Interconnect

• Ethernet Switch
• 100BaseT (Fast Ethernet)
• 10 MB/sec (100Mb/sec)
• Gigabit Ethernet
• Typically delivers 30-60 MB/sec
• 100-1000 microsecond latency
• 10 Gigabit
• latest
• possible replacement for Myrinet
• Myrinet 2000
• 200 MB/sec
• 10-15 microsecond latency
• scales to 1000s of nodes
• 30 of total cost

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Hardware User Interface

• Head/user tracking
• radio/accelerometers
• video tracking
• Ascension spacepad
• 1600.00
• needs isa slot
• 6 DOF mice
• Ascension Flock of Birds
• handheld computer
• VRCO trackd (software)
• http//www.ascension-tech.com

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Hardware Mounting/Alignment
ANL Positioner

• 6 DOF adjusters
• independent control
• stepper motor/ remote control
• auto alignment
• camera feedback loop
• image warp
• http//www.merl.com/projects/ProjectorCalib

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Hardware Audio

• Covered in later session

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Software Cluster Administration

• Kickstart
• RedHat network installer
• xCAT
• utilities for cluster monitoring, remote
  execution, installation, etc
• IBM commercial product
• http//x-cat.org
• Performance Co-Pilot
• System level performance monitoring
• http//oss.sgi.com/projects/pcp/
• Batch
• OpenPBS
• http//www.openpbs.org
• LSF
• http//www.platform.com/products/clusterware

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Software System (multi-display)

• WireGL/Chromium
• VRJuggler, NetJuggler
• CaveLib, trackd
• Syzygy
• softGenlock
• http//graphics.stanford.edu/software/wiregl
• http//sourceforge.net/projects/chromium
• http//graphics.stanford.edu/humper
• http//www.vrjuggler.org
• http//www.vrco.com/products/cavelib/cavelib.html
• http//www.isl.uiuc.edu/ClusteredVR/ClusteredVR.ht
  m
• http//netjuggler.sourceforge.net
• http//netjuggler.sourceforge.net/SoftGenLock.php

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Software Graphic APIs and Libraries

• OpenGL
• Open Inventor
• OpenGL Performer v2.5
• Kitware VTK
• http//www.sgi.com/software/opengl
• http//oss.sgi.com/projects/inventor
• http//www.tgs.com
• http//www.sgi.com/software/performer
• http//www.kitware.com

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Software Development

• Covered in later session

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Software Tools

• Tiled Window Managers
• NCSA
• MoviePlayers
• NCSA Pixel Blaster
• Argonne Movie Player
• Synchronization Libraries
• Communication Libraries (DAFFIE)
• http//www.ncsa.uiuc.edu/TechFocus/Deployment/DBox
  
• http//scv.bu.edu/SCV/DAFFIE

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Software Application design

• Multi-channel
• local compute/local render
• IR multi-channel
• Clent/Server
• local compute/distributed render
• WireGL/Chromium
• Master/Slave
• distributed compute/distributed render (mixed
  compute/render)
• Syzygy, VRJuggler, Performer synchronization

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Software Application design
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Implementation Issues

• Type of Stereo (active vs. passive)
• Type of Projection (front vs. rear)
• Projector Control
• Projector Mounts
• Projector Alignment
• Projector Color and Luminosity Matching
• Luminosity Falloff within a tile
• software computation of inverse filter applied
  during rendering
• Edge Blending

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Implementation Issues

• Physical Space
• projector -gt projector
• projector -gt screen Airflow
• Cooling
• Light
• leaks
• ambient
• Power
• Head tracking

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Maintenance Issues

• Alignment
• Color and Luminosity Matching
• Power Down
• Bulb usage

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Resources

• Stereo
• http//www.stereoscopy.com/links/index.html
• http//www.stereographics.com/homepage/frame-wp.ht
  ml
• http//astronomy.swin.edu.au/pbourke/stereographi
  cs
• Walls
• http//scv.bu.edu/Wall
• http//www-fp.mcs.anl.gov/fl/activemural
• http//www-fp.mcs.anl.gov/fl/publication
• http//www.ncsa.uiuc.edu/TechFocus/Deployment/D
  Box
• http//www.cs.princeton.edu/omnimedia

35
Resources

• VR/Multigraphics
• http//graphics.stanford.edu/projects/multigrap
  hics
• http//www.evl.uic.edu/pape/CAVE/linux

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Current Projects

• Projector Mount Design
• Projector Control Software
• Auto Projector Alignment
• Auto Projector Color and Luminosity Matching
• Edge Blending
• User Interface Devices
• AG integration

37
Conclusions

• Linux is a cost effective and rich environment
  for building large scale tiled display walls.