Dr. cheryl Seals

1
3D User Interface Output Hardware

• Dr. cheryl Seals
• 11/2008
• Modified from slides by Yuan Tian
• For COMP6620
• 11/06/07

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Agenda

• Visual Displays
• Characteristics, Depth cues, Device
• Audio Displays
• Sound localization cues, 3D Sound generation,
  System configuration
• Haptic Display
• Haptic cues, Characteristic, Display types

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Visual Displays

• Visual Display characteristics
• Field of Regard and Field of View
• Field of Regard(FOR) the amount of physical
  space surrounding the user in which visual images
  are displayed.
• User stands in a cylindrical display, FOR360
• Field of View(FOV) the angular extent of the
  observable world that is seen at any given
  moment.
• A flat projection screen, horizontal FOV80120
• A display devices FOV must max FOV of human
  visual system(about 200 degrees)
• A visual display device can have a small FOV but
  still have a large FOR.
• For example a head-mounted display, FOV40
  FOR360

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Visual Display characteristics

• Spatial resolution
• Related to pixel size and is considered a measure
  of visual quality
• Measure is given in dots per inch(dpi)
• Resolution ? Number of pixels
• Users distance to the visual display device also
  affects the spatial resolution on a perceptual
  level.
• Screen geometry
• Nonrectangular screen shapes require nonstandard
  projection algorithms, which can affect visual
  quality.
• Light transfer mechanism
• How light gets transferred onto the display
  surface
• Front projection, rear projection, laser light
  onto the retina, use of special optics, etc

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Visual Display characteristics

• Refresh rate
• Speed with which a visual display device
  refreshes the displayed image from the frame
  buffer. (Hz)
• Ergonomics
• Comfort
• Unobtrusive

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Visual Displays

• Depth cues
• Monocular, static cues
• Depth information that can be inferred from a
  static image viewed by a single eye.
• Relative size, height relative to the horizon,
  occlusion, linear and aerial perspective, shadows
  and lighting, and texture gradients.

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Depth Cues

• Oculomotor cues
• Derived from muscular tension in the viewers
  visual system
• Accommodation Convergence

Accommodation
Convergence
Accommodation- physical stretching and relaxing
of the eye lens caused by the eye muscle when
focusing on an image Convergence- the rotation of
the viewers eyes so image can be fused together
at varying distance
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Depth Cues

• Motion parallax
• Depth information is conveyed when objects are
  moving relative to the viewer, or when the viewer
  is moving relative to stationary objects.
• Binocular disparity and stereopsis
• Difference between two images viewed from two eyes

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Visual Displays

• Visual Display device
• Monitors
• Surround-screen displays
• Workbenches
• Hemispherical displays
• Head-mounted displays
• Arm-mounted displays
• Virtual retinal displays
• Autostereoscopic displays

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Audio Displays

• 3D sound localization cues
• Binaural cues
• Arise from a comparison of the sound waves
  received by each ear.
• Two important cues for determine the sound
  sources lateral location - Interaural time
  difference(ITD) and Interaural intensity
  difference(IID)
• Ambiguous situation (font, behind, above, below)
  IIT 0, IID0
• Spectral and dynamic cues
• The frequency spectrum of a sound source varies
  with respect to source distance because of
  absorption effects.
• Head-related transfer functions(HRTFs)
• Spatial filters that describe how sound waves
  interact with the listeners torso, shoulders,
  head, and particularly the outer ears.
• Modify the sound waves from a sound source in a
  location-dependent manner.
• Problem Listener specific, do not contain any
  reverberation information.

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3D sound localization cues

• Reverberation
• Collection of reflected waves from various
  surface within a space
• Aid in the perception of source distance, not
  direction
• Sound Intensity
• Vision and Environmental Familiarity
• A listeners prior experience with a particular
  sound and environment can affect the listeners
  ability to determine the sound sources location.

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Audio Displays

• 3D sound system configuration
• Headphone
• Pros Avoid crosstalk Isolate the user from
  external sounds Allow multiple users to receive
  3D sound simultaneously
• Cons Inside-The-Head localization(IHL) can be
  cumbersome and uncomfortable to wear for long
  time
• External Speakers
• Pros no additional device for user
• Cons must avoid crosstalk difficult to present
  3D sound for more than one head-tracked user
  sound may be filtered through real-world objects

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Audio Displays

• Audio in 3D interface
• Localization
• Sonification
• Ambient effects
• Sensory substitution
• Annotation and help

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Haptic Displays

• Haptic cues
• Tactile cues
• Perceived by a variety of cutaneous receptors
  located under the surface of the skin.
  Mechanoreceptors, Thermoreceptors, Nocireceptors
• Kinesthetic cues
• Perceived by the muscles, joints and tendons of
  the body to produce information about joints and
  angles and muscular length and tension
• Effects of Tactile and kinesthetic cues on haptic
  perception
• One cue or both are applied. Ex. Handshaking

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Haptic Displays

• Haptic display characteristics
• Haptic presentation capability
• What type of information does the haptic display
  provide to the user?
• Resolution
• Spatial resolution- the minimum proximity of the
  stimuli presented to the user
• Temporal resolution refresh rate of the display
  
• Ergonomic
• Safety
• User comfort

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Haptic Displays

• Haptic display characteristics
• Haptic presentation capability
• What type of information does the haptic display
  provide to the user?
• Resolution
• Spatial resolution- the minimum proximity of the
  stimuli presented to the user
• Temporal resolution refresh rate of the display
  
• Ergonomic
• Safety
• User comfort

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Haptic Displays

• Haptic display characteristics
• Haptic presentation capability
• What type of information does the haptic display
  provide to the user? Informs with touch.
• Resolution
• Spatial resolution- the minimum proximity of the
  stimuli presented to the user
• Temporal resolution refresh rate of the display
  
• Ergonomic
• Safety
• User comfort

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Haptic Displays

• Haptic display types
• Ground-referenced
• Body-referenced
• Tactile
• Combination
• Passive

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Choosing output devices for 3D User Interface

• It is a difficult task and there is no single
  rule of thumb telling developers which output
  devices to use
• There are many factors to consider such as
  finances, restrictions, ergonomics
• Most important consideration-application
• Analyze the applications goal and its
  underlying operations and tasks to obtain
  direction in choosing an appropriate output
  device.

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Thanks