VR Gadgets part 2

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VR - Gadgets(part 2)

• Jyun-Ming Chen
• Fall 1999

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Contents

• Part 1
• 3D position sensors
• Trackballs
• 3D probes
• Sensing glove

• Part 2
• Stereo viewing
• 3D sound
• Force feedback
• Other sensors

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Viewing Devices

• vision the most important sensorial channel for
  human
• immersive illusion
• depth perception
• wide field of view
• stereo imaging
• interactivity

• options
• HMD head mounted display
• HUD head-up display
• BOOM
• stereo glasses
• VRD virtual retinal display
• Responsive Workbench

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Physiological Model

• convergence
• parallax
• field of view (fov)
• task
• design a display that can adequately provide this
  stereo and immersive sensation

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HMD

• basic components
• optics focus increase fov
• screen CRT or LCD
• enclosure hold components provide occlusion
• design concerns
• ergonomics (wt. comfort)
• image quality
• tracking

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HMD (cont)

• CRT (vs. LCD)
• better resolution
• often reflective (not good to directly look into
  in short distance)
• heavier
• for hi-end HMD (military flight simulation)
• BOOM

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BOOM

• binocular omni-orientation monitors by Fakespace
  Inc.
• pros
• no magnetic field effects (tracking)
• high update rate, low noise (tracking)
• allow intermittent use of kbd
• cons
• kinematic deadzone

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Boom Films
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Cyberscope

• low cost passive no head tracking
• rather than surrounded by a virtual world, the
  user views the display as a window into the
  virtual world
• view pos change scene change
• view orient change scene remains

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Stereo Glasses

• group viewing
• cannot afford to give everyone an HMD
• technology
• shutter glasses
• r/b glasses
• spatial multiplexing image (SMI)
• responsive workbench

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SMI
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SMI (cont)

• Principles
• ltpolarizationgt
• Advantages
• single image (require no special monitor)
• cheap passive glasses
• same technology applies to printing

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Responsive Workbench

• www-graphics.stanford.edu/
• projects/RWB/newindex.html

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Virtual Retina Display

• www.hitl.washington.edu/projects/vrd

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Stereograms

• Bela Julerz (1971), Bell Lab
• perceptual research on random dot pattern
• Proves that the differences in horizontal
  positioning of objects in the LR images is the
  basis for depth perception
• prior to this, it was believed that depth
  perception was based on first recognizing the
  object, then determine he angle between the eyes
  as theyre focused on the object

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Random dot example
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3D Sound

• important for immersive experience
• Stereo sound vs. 3D sound
• cp. DirectSound

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Human Hearing Model

• Cues for sound localization
• ITD (interaural time difference)
• IID (interaural intensity difference)
• no info of front back
• head, torso, pinna scattering

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Measuring HRTF

• head related transfer function
• some data commercially available

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Using HTRF

• virtual sound position should be changed
  according to head position
• Foster estimates 30-50 MIPS for each sound source
• even more expensive for reflected sounds

• convolvotron
• source position corresponding HRTF
• convolution
• D/A, then headphone
• commercial cards
• Acoustetron, Beachtron
• no. of sound sources, reverberation allowed,
  Doppler effects, ...

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Force Feedback

• important channel of information
• training surgeon on virtual bodies, ...
• limited to hand and wrist only
• not whole body ... no virtual sex yet
• classification
• touch vs. force feedback

• touch
• contact surface geometry
• smoothness
• temperature
• slippage (due to gravity)
• force
• total contact force
• contact surface compliance
• weight (light, heavy)
• examples

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VR Concerns

• replicate contact forces, surface geometry,
  smoothness, slippage, ... in real time
• safety
• force large enough to stop (from penetration)
• yet not to harm operators

• technology
• hydraulic
• powerful, expensive, dirty
• pneumatic
• cheap, clean, safe
• portability
• desktop, self-contained (no massive piping)

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Touch Feedback

• possible implementations
• visual
• vibro-tactile
• electro-tactile
• neuromuscular
• pneumatic

• already available in many archive games

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Teletact Glove

• 2 single-lining Lycra glove
• 30 air pockets
• generate tactile patterns as in grasping
• each pocket with 2 tubes (intake, exhaust)
• air by small compressor
• finger tip pockets to simulate slippage
• concern response rate

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Programmable Tactile Simulator

• motivated by Braille system
• light-wt shape memory metal
• current, heated, shrink, up
• spatial control
• geometry of touch surface
• temporal control
• vibratory sensation
• slippage

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Force Feedback

• possible technology
• arms
• joysticks
• portable masters
• related to teleoperation

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Force Feedback in VR

• wrist force sensor
• graphics display of virtual objects arm
• encoder records arm configurations
• computed feedback force D/A converter drive
  motor

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FFB Devices
Phantom
EXOS
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Other (Exotic) Sensors

• Biosensors
• muscle skin electricity
• eye tracking
• compare gaze tracking devices
• brain wave
• Vision-based sensors
• totally unencumbered VR experience
• ?????

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Vision-based Trackers
Image Glove
Large Volume Tracking
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Review Questions

• Survey (in greater detail) human eye model
• Survey principles of polarization describe how
  SMI works
• Survey home theatre system AC-3, Dolby Digital,
  DTS, THX Survey what Microsoft DirectSound
  offers.
• Survey principles of convolution
• Describe applications where force and/or touch
  feedback is essential
• Survey arcade games where force feedback is used
  (with pictures)
• Describe in detail how the two vision-based
  trackers work
• Survey gaze tracking