Output Devices Chapter 3 Burdea

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Output DevicesChapter 3 Burdea
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Output Devices

• Visual
• Auditory
• Haptic

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Visual Devices

• Dimensions
• Stereoscopic/monoscopic
• Image resolution
• Field of view
• Display tech
• Ergonomic factors
• Cost

4
Eye

• 126 million photoreceptors
• Eye-gaze technology not useful yet
• Why?
• Impact of not knowing eye gaze location?
• IPD
• 53-75 mm

5
HMD

• Tradeoff between FOV and resolution
• Why?
• LCD for lower end
• CRTs for higher end (higher resolution)
• Newer HMDs LCOS
• Inputs
• VGA, NTSC/PAL

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Hand Mounted Displays

• Binoculars
• 1280x1024
• 19900

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Floor Supported Displays

• Articulated mechanical arm
• Offload weight
• 0.2 ms Latency
• High accuracy
• 0.1 degree orientation error
• Pole in the way
• Limited Space (6 diam, 3 hgt)
• Good FOV
• Good resolution (1280x1024)
• Fakespace Boom3C
• WindowsVR
• Differences
• Stereo
• Tracking
• Advantages
• Applications

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Desk Supported Displays

• Fishtank VR
• Autostereoscopic Displays
• Addresses weight fatigue
• Tracking?
• DTI 2018XL Virtual Window
• Elsa Ecomo4D

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Monitor Large Volume Displays

• Multiple people
• Monitor Based LVD
• Fishtank VR
• With limited FOV, what is a possible solution?
• Exaggerate tracking
• More monitors (synch, bezel)
• Most use active stereo (shutterglasses)
• 29-32 transmittance
• 100-800
• Can be used for prolonged periods

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Projector LVD

• Workbench
• CAVE
• 300-500k with SGI
• 100k with PC clusters
• Issues?
• Large wall displays

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Sound Displays

• What are good goals for VR Sound Displays
• Compare importance to
• Movies
• Video Games
• What role does sound play?
• Interactivity
• Immersion
• Perceived image quality(!)
• Dimensions
• Mono/Stereo/virtual sound
• Tracker
• Occlusion
• What does it take to uniquely place a sound
  source?

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3D Sound

• Fig 3.21
• Azimuth Cues
• Interaural Time Difference
• ITDhead radius/speed of sound(?sin ?)
• Interaural Intensity Difference
• High frequency
• Head shadow effect
• Elevation Cues
• How are ears modeled?
• If simple holes what is the problem?
• Pinna effects sound propagation
• Frequency attenuation and amplification

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3D Sound

• Range Cues
• Intensity
• Motion Parallax
• As the user moves his/her head, the changes in
  azimuth
• Head Response Transfer Functions
• Put two microphones at the ears
• Record sounds (HR impulse responses)
• Corresponding Fourier transforms (HRTFs)
• Depends on sound frequency
• No two people are exactly the same
• Given HRTFs
• Take sound
• Apply filter
• Get two signals that should replicate the sound
  to the user
• Convolving
• However whats the effect of using another
  persons HRTF?

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Sound Display Hardware

• Offload compuational load
• Convolvotron
• Crystal River
• First virtual 3D sound Generator
• NASA 1988
• Real-time DSP
• Calculate new HRTFs given
• Sound
• Head position (tracker)
• Audigy
• Soundblaster EAX/ Aureal A3D
• Simple geometry
• Occlusion, reflection
• Tracking?
• High-end SDKs - 14k

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Speaker Layouts

• Stereo
• Quad speakers
• 5.1 surround sound (6.1/7.1)
• Multiple users?

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Haptic Feedback

• Hapthai touch
• Greatly improves realism
• When is it needed?
• Other cues occluded/obstructed
• Required for task performance
• High bandwidth!
• Why are hands and wrist the most important?
• High density of touch receptors
• Full body are still in research and not very
  usable (back, body)
• Two kinds of feedback
• Touch Feedback information on surface geometry,
  roughness, temperature, etc. Does not resist
  user contact
• Force Feedback information on compliance,
  weight, and inertia. Actively resists contact
  motion

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Passive Haptics

• Not controlled by system
• Pros
• Cheap
• Large scale
• Accurate
• Cons
• Not dynamic
• Limited use

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Active Haptics

• Actively resists contact motion
• Dimensions?
• Force resistance
• Frequency Response
• Degrees of Freedom
• Latency
• Intrusiveness
• Safety
• Comfort
• Portability

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Human Haptic System Sensors

• Meissner and Pacinian
• Quick (high frequency) sensors (50-300 Hz)
• Vibration, acceleration
• Low resolution
• Merkel and Ruffini - Slow (low frequency)
  adapting (0-10 Hz)
• Constant, surfaces, edges
• High resolution
• Thermoreceptors temperature
• Proprioceptors/Kinesthesia
• Perception of own body motion
• Page 96

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Tactile Feedback Interfaces

• Goal Stimulate skin tactile receptors
• How?
• Air bellows
• Jets
• Actuators (commercial)
• Micropin arrays
• Electrical (research)
• Neuromuscular stimulations (research)

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Tactile Mouse

• Logitch iFeel Mouse
• Electrical Actuator
• Shakes up and down (do not disturb XY motion)
• Mouse over buttons
• Haptic Bump
• Rumble Pack

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CyberTouch Glove

• CyberGlove
• Immersion Corporation
• Six Vibrotactile actuators
• Back of finger
• Palm
• Off-centered actuator motor
• Rotation speedfrequency of vibration (0-125 Hz)
• When tracked virtual hand intersects with virtual
  object, send signal to glove to vibrate
• 15000

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Force Feedback Devices

• Attempts to stop the users motion if necessary
• Larger Actuators
• Grounded
• Mechanical bandwidth - perceived frequency of a
  haptic interaction (in Hz)
• Control bandwidth system control bandwidth to
  device

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Force Feedback Joysticks

• WingMan Force 3D
• Inexpensive (60)
• Actuators that can move the joystick given system
  commands
• Max 3.3 N of force
• Force feedback driving wheel

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SensAble PHANToM Arm

• 3 and 6 DOF force feedback device
• Most popular (1000) in VR research
• 3 DC motors
• Little interitia/friction
• 6.4 N (1.7 continuous)
• Control loop 1000 Hz
• 1500 Omni
• 16000 standard Desktop
• 56000 6 DOF high end

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Other Force Feedback

• Large Forces
• Haptic Master Arm
• 250 N
• Sarcos Arm
• http//www.princeton.edu/jmelli/papers/ch4-haptic
  s.pdf
• Gloves
• CyberGrasp
• 39000
• CyberForce
• 56000

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Why is it hard?

• Control bandwidth
• Mechanical bandwidth
• Forces
• Hygiene
• Gender differences
• Portability
• Encumbrance
• Solutions?
• Specific engineering