Virtual Reality Components

1
Virtual Reality Components

• Sven Loncaric, Ph.D.
• Faculty of Electrical Engineering and Computing
• University of Zagreb
• E-mail sven.loncaric_at_fer.hr
• WWW http//ipg.zesoi.fer.hr

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Overview of Presentation

• VR hardware
• VR software
• VR systems
• Virtual Reality Modeling Language (VRML)

3
VR Hardware

• Primary input devices (3D pointing devices,
  whole-hand, and whole-body inputs)
• Tracking devices
• Output devices (visual, auditory, haptic, motion,
  olfactory)
• Computer workstations (various platforms)

4
Primary Input Devices

• 3-D pointing devices
• 3-D mouse
• 3-D digitizer
• Whole-hand inputs
• gloves
• exoskeleton devices
• Whole-body inputs

5
3D Pointing Devices

• Support menu item and object selection and a
  number of programmable buttons
• This is similar to conventional 2D pointing
  devices that are used as conventional human
  computer interface devices
• The choice of the device type depends on the
  degree of how much the device is appropriate for
  a particular user interface

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3D Mouse

• 3D mouse has 6 degrees of freedom (position
  coordinates and angles)
• Example Ascension 6DOF mouse

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3D Digitizer

• Digitizes 3D coordinates of points in space
• Useful for creating 3D objects for building
  virtual worlds
• Example Immersion Corp. Microscribe 3D

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Whole-Hand Inputs

• Whole-hand input is required for the use of the
  hands capabilities for the control of various
  tasks
• VR systems attempt to provide means for natural
  human-computer interaction
• One approach to human-computer interaction is by
  hand gestures
• Human hand has 29 degrees of freedom

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Glove-based Devices

• Gloves measure information about the position of
  the hand and hand gestures
• Example
• Virtual Technology CyberGlove
• Has18 or 22 sensors (degrees of freedom)
• Price range 10.000-15.000

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Suit-based Devices

• Suits measure positions of ankles, hip,
  shoulders, arms, and hands
• There are wired and wireless versions
• Example Virtual Technology, Inc.
• Initially developed for NASA applications such as
  measurement of biomechanics during space missions

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Exoskeleton Devices

• Exoskeleton devices use an external mechanism
  attached to the users hand or arm
• It is used for tracing the movements of the hand
  or arm
• Exoskeleton devices can be constructed to provide
  a force feedback (e.g. when reaching a virtual
  object)
• Example Dexterous Arm Master (Sarcos, Inc.)

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Tracking Devices

• Tracking devices are usually used to measure the
  motion of the users head and hands, and eyes
• 6 degrees of freedom are required to describe the
  position and the orientation of the object in 3-D
  space
• Tracking devices can be electromagnetic,
  mechanical, optical, acoustic (ultrasound), or
  inertial
• tracking device quality depends on resolution,
  accuracy, and system responsiveness (sample rate,
  data rate, update rate)

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Head and Hand Tracking

• Magnetic trackers are most popular
• the receiver is placed on the object (e.g. head
  or hand)
• the transmitter sends the signals
• the electronic unit determines the position and
  communicates it to the computer
• Most popular high-end trackers are
• Fastrack (by Polhemus)
• Flock of Birds (by Ascension)

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Eye Tracking

• Eye-tracking systems measure the direction of the
  eyes by detecting the movement of the fovea
• The information about the users gaze can be
  used to control some actions (e.g. updating the
  virtual scene, controlling some devices)
• This is one step towards the intriguing idea of
  using human nervous system to control virtual
  objects (connection between human nervous system
  and computer)

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Eye Tracking Principles

• According to the measurement approach eye
  trackers are divided into the following groups
• optical (users gaze is determined using
  reflections from the eye surface)
• electroocular (corneoretinal potential is
  measured via skin electrodes)
• electromagnetic (measures induction in a magnetic
  coils attached to a lens on the eye)
• Most commercially available eye trackers are
  optical
• Eye tracker price range 10,000 - 100,000

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Output Devices

• visual displays
• auditory interfaces
• haptic interfaces
• motion devices
• olfactory interfaces

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Visual Displays

• A VR visual display must provide a stereoscopic
  view of the virtual environment
• Head tracking must enable continuous updating of
  the stereoscopic view
• The factors that affect the quality of a display
  are
• resolution
• color vs. black and white
• brightness
• motion representation
• ergonomic and health concerns

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Type of Visual Displays

• head-mounted displays (used for immersive VR)
• boom-mounted displays
• stereoscopic glasses
• projectors

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Head Mounted Displays

• Each eye has a separate display
• Optics that allow user to focus at some depth and
  not the surface of the display screen
• The displays and optics are mounted in a helmet
  type device
• Often there are also position tracking devices
  and headphones mounted on the helmet
• A new version of HMDs are under development where
  image is projected directly on the retina
  (retinal displays) instead being projected to the
  screen

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Head Display Screens

• Display screens can be
• transparent (surrounding environment is visible,
  e.g. for pilots, for augmented reality)
• opaque (surrounding environment is not visible,
  for virtual reality)
• Important HMD quality factor is the field of view
  (the larger, the better)
• HMD price range 1,000 - 250,000

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Stereo Visualization

• Stereo display is required to produce 3-D view of
  the virtual environment
• For stereo visualization two different images
  corresponding to the left and right views at the
  scene must be generated for left and right eyes
• 3-D stereo visualization can be obtained using
• Active glasses
• Passive glasses
• Autostereoscopic systems

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Active Glasses

• In active glasses shutters are mounted instead of
  the lenses
• The shutters are monochrome LCDs displaying
  opaque image on one eye and transparent image the
  other and vice-versa
• The user looks at a CRT monitor or projector
  screen that shows left and right image and
  generates a synchronization signal that controls
  the shutter glasses

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LCD Shutter Glasses

• Example Crystal Eyes (by Stereographics, Inc.)
• Uses infra red emitter to synchronize the glasses
  with the display showing left and right images
• Several glasses can be synchronized by one
  emitter to provide stereo viewing for several
  people
• Price 1000

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Passive Glasses

• For passive glasses left and right images are
  displayed on a CRT monitor in either
• different colors (e.g. red and blue colors, red
  and blue glasses are used),
• or different polarizations (glasses with
  differently polarized lenses are used)

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Autostereoscopic Systems

• User does not need any type of glasses or helmet
• Stereo effect is achieved by a variety of
  techniques
• lenses in front of the display screen
• vertical bars in front of the screen prevent eyes
  seeing the same image

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Auditory Display

• Most VR projects are concerned with visual
  display and do not pay much attention on auditory
  aspect of simulation
• Auditory feedback speeds up the completion of
  tasks
• Some authors have successfully used the auditory
  feedback to replace the force feedback
• Auditory stimulus improves the impression of
  being immersed in a virtual environment
• Use of sonification in graphical user interfaces
  (GUI) to solve the problem of overcrowded GUIs
  (using earcons)

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Auditory Interfaces

• 3D audio effects include
• Doppler shifts for moving sound sources
• spatialization
• acoustic ray tracing
• 3D source position control
• user selectable environment size and materials
• Commercial available audio processing systems
  range in price from 500-20,000

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Haptic Interfaces

• The human haptic system plays an important role
  in object manipulation
• Two main components of the haptic sensory system
  are
• Tactile sensors
• Force feedback
• Tactile sensors provide information about object
  geometry and surface texture
• Force feedback is important when user applies a
  force to move the object
• Force feedback helps to guide manipulation of
  objects

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Tactile Interfaces

• Example CyberTouch (by Virtual Technologies,
  Inc.)
• vibration stimulation on each finger of the
  CyberGlove
• Virtual objects can be felt

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Force Feedback Technologies

• Force feedback devices are based on the following
  technologies
• electromagnetic motors
• hydraulics (hydraulic fluids)
• pneumatics (pressurized air)
• piezoelectric motors (translate vibration to
  linear motion)
• magnetostrictive (change shape in magnetic field)
• shape memory alloy

31
Force Feedback Devices

• 4 DOF Force Feedback Master (surgical simulation
  of minimally invasive surgery)
• Force Exoskeleton ArmMaster

32
Full Body Motion Interfaces

• Still immature but some systems are commercially
  available
• Motion systems provide
• passive user movement through the virtual
  environment
• A cabin is mounted on a motion platform (tank and
  flight simulators, games)

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Passive User Motion

• User is in a vehicle (cabin) that moves through
  the virtual environment
• The cabin is mounted on a motion platform which
  is controlled by a computer
• Used for tank and flight simulators (US
  Department of Defense)
• Game simulators

34
Self-Motion Systems

• Used when the user moves itself through the
  virtual environment as opposed to being passively
  moved in a vehicle
• Types of self-motion systems are
• gyroscope platforms (rotate user freely in 6 DOF)
• revolving backpacks
• hang gliders
• tilting motion platforms

35
Olfactory Interfaces

• Olfactory interfaces are the least developed of
  all interfaces
• The main reason is the lack of useful
  applications
• Olfactory interfaces refer to
• systems for collecting and interpreting odors
  (electronic noses)
• systems for delivering olfactory cues

36
Electronic Nose

• Technologies for collecting and interpreting
  odors are developed for
• military applications in biological and chemical
  warfare
• product quality control
• Three basic sensing technologies are
• gas chromatography
• mass spectrometry
• chemical sensor arrays

37
Delivering Olfactory Cues

• Odorant storage is required for storing the odors
  before they are released
• The most popular method is microencapsulation of
  odorants which is the basis for scratch-and-sniff
  patches
• The most difficult problem in delivery of various
  odors is air ventilation after an odor is no more
  required
• There are several commercial olfactory delivery
  systems available on the market

38
VR Software

• Software is used for
• design of virtual environments (general purpose
  3-D CAD programs or specialized VE development
  applications)
• simulator software packages for running VR
  applications in real-time
• Simulations in real-time require powerful
  computers that can perform real-time computations
  required for generation of visual displays

39
VE Development Software

• 3D development software is required to create
  virtual environments
• Conventional CAD programs can be used for this
  purpose
• Specialized VE development software is also
  available

40
VR Simulation Software

• Support for a wide spectrum of VR interfaces
• Contain control programs for VR simulations
• Examples of VR development software packages
• World Tool Kit (Sense8)
• CDK (Autodesk)
• dVise
• Superscape VRT
• VREAM

41
VR Systems

• A number of general purpose VR systems have been
  developed including
• CAVE (scientific visualization)
• ImmersaDesk
• Infinity Wall

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CAVE VR System

• Developed by Univ. of Chicago
• Scientific visualization
• Accomodates several people
• 3D video and audio environment
• Stereo glasses, wand, tracking
• SGI Onyx 3 Reality Engines

43
ImmersaDesk

• Univ. of Chicago
• A drafting table format
• Uses stereo glasses and head and hand tracking
• Rear projection screen
• Powered by SGI Onyx or Indigo 2

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VRML

• Virtual Reality Modeling Language (VRML) is a
  language for description of 3D scenes with
  multimedia content
• VRML transfer and viewing of 3D virtual worlds
  using HTTP protocol on Internet
• VRML is a subset of SGI Open Inventor language
• SGI is a main sponsor of the language
• VRML 1.0 the first version of the language
  (1995)
• VRML 2.0 the second version of the language
  (1996)
• VRML 97 is ISO standard accepted in 1997
  describing the language

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VRML

• VRML is compatible with JAVA language
• VRML is suitable for representation of 3D
  environments on the Internet
• There are VRML plugins available for popular WWW
  browsers such as Explorer and Navigator
• Design of VRML environments
• converters are available between many 3D CAD
  formats and VRML
• specialized programs are available for VRML world
  design

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Conclusion

• Most components required for the design of VR
  systems are commercially available
• VR technology is becoming more affordable
• it is possible to develop VR applications on
  Windows NT personal computers (PCs)
• prices of components start under 1000
• Advances in computer hardware reduce the price
  and enable new applications