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Teil 3:VR – Eingabegeräte
Virtuelle RealitätWintersemester 2007/08
Prof. Bernhard Jung
Prof. B. Jung Virtuelle Realität TU Freiberg
Overview
Continuous input devicesTrackerData gloves
Discrete & hybrid input devices Mouse-type input devices
MiscellaneousPlatformsSpeech…
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Prof. B. Jung Virtuelle Realität TU Freiberg
Information Flow in VR-Systems
Source: Sherman & Craig, 2005
Prof. B. Jung Virtuelle Realität TU Freiberg
Virtual Reality Experience Source: Sherman & Craig, 2005
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Prof. B. Jung Virtuelle Realität TU Freiberg
User input to the virtual world
User monitoring is the real-time monitoring of the participant's actions in a VR experience
Continuous tracking of user movements (body tracking). allows the system to render and display the virtual world from the user's egocentric perspective -- providing the effect of physical immersion.
Discrete user-initiated inputsallows the user to indicate to the system that an action should be takene.g. pressing a button or speaking a command to the system
Prof. B. Jung Virtuelle Realität TU Freiberg
Discrete / event-basedContinuous / sampledHybridsMiscellaneous input
speechlocomotion devices
Input device characteristics
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Prof. B. Jung Virtuelle Realität TU Freiberg
Generate one event at a timeEvent queueExamples:
buttonskeyboardspinch gloves
Discrete input devices
Prof. B. Jung Virtuelle Realität TU Freiberg
Continuous input devices
Produce steady stream of dataSampled at various times by the system for “snapshot” of stateExamples:
trackersdata glovespotentiometers
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Prof. B. Jung Virtuelle Realität TU Freiberg
Tracking systems
Measure position and/or orientation of a sensor6 degrees of freedom in space
Most VEs track the head and the hand(s) Spatial input devices
free-space interaction
Tracked real objects resembling virtual objectsMotion capture
Prof. B. Jung Virtuelle Realität TU Freiberg
Electromagnetic Tracker
6DOF Magnetic tracker & DataGlove
6 DOF tracking (position & orientation)Transmitter
Creates three orthogonal low-frequency magnetic fieldsShort range version: < 1mLong range version: < 3m
Receiver(s)Three perpendicular antennas Distance is inferred from the currents induced in the antennas
DistortionsNoisy – requires filteringAffected by metal – requires non-linear calibration
Rather large sensors (1-2cm)
Transmitter
Receiver
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Prof. B. Jung Virtuelle Realität TU Freiberg
Wireless suit (Ascension Technology)Sensors: 20/suit
100 updates/sec3 meters rangefrom base unitResolution<2 mmand <.2 degrees
Electronic unit(2 hours battery life)
Prof. B. Jung Virtuelle Realität TU Freiberg
Optical Trackerpassive
IR light reflecting markerCombined to unique spatial configuration per tracked position
activeIR light emitting markerSequential activation: trivial identification of single markersrequires cabling & batteries
2 or more IR camerasAdvantages
No interference with metalLow latencyHigh resolution
DisadvantagesLine of sight issues (more cameras help)
6DOF optical tracker by ART
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Prof. B. Jung Virtuelle Realität TU Freiberg
Optical Tracker
6DOF optical tracker by ART
Prof. B. Jung Virtuelle Realität TU Freiberg
Real-Time Motion Capture
www.ptiphoenix.com
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Prof. B. Jung Virtuelle Realität TU Freiberg
Mechanical Tracker
Very accurate and preciseVery fastMechanical linkage places an unnatural inertia on the userMechanical linkage can prevent the user from moving to some locationsForce feedback can be integrated into the system
Video: HMD SutherlandBoomPhantom
Prof. B. Jung Virtuelle Realität TU Freiberg
Uses ultrasoundTypical setup for 3 DOF
3 microphones1 speaker
Distance is inferred from the travel time for the sound
Triangulation allows the location of each microphone/speaker to be determined
AdvantagesNo interference with metalRelatively inexpensive
DisadvantagesLine of sight issuesSensitive to air temperature and certain noises
Logitech Fly Mouse
Acoustic Trackers
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Prof. B. Jung Virtuelle Realität TU Freiberg
Inertial trackers
Intersense IS-300Less noise, lagOnly 3 DOFs (orientation)Use gyroscopes and accelerometers
inexpensiveCan lose accuracy over time
a gyroscopesource: wikipedia
Prof. B. Jung Virtuelle Realität TU Freiberg
E.g. Intersense IS-600 / 900inertial (orient.)acoustic (pos.)
E.g. Ascension HyBirdoptical (position + orientation)inertial (orientation)
Hybrid Trackers
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Prof. B. Jung Virtuelle Realität TU Freiberg
E.g. Nintendo Wii Remote optical position & orientation tracking
uses built-in one-megapixelimage sensor
+ stationary sensor bar with 8 IR LEDs
+ orientation tracking using acceleration/tilt sensors
used when device is pointed away from sensor bar
Hybrid Trackers
wikipedia
nintendo-europe.com
wii.nintendo.com
Prof. B. Jung Virtuelle Realität TU Freiberg
Tracking Technology: Pros and Cons Overview
Acc
urac
y
Late
ncy
Drif
t
Line
Of
Sigh
t
Wire
less
Sens
or W
eigh
t
Sens
or S
ize
Magnetic - - + + - + - Optical (active) + + + - 0 + +
Optical (passive) + + + - + + - Acoustic 0 + + - + - - Inertial - + - + 0 0 0
Acoustic / Inertial 0 + + +/- 0 - -
(based on Kuhlen & Assenmacher)
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Prof. B. Jung Virtuelle Realität TU Freiberg
Used to track the user’s finger movementsfor gesture and posture communication
Almost always used with a tracker sensor mounted on the wristCommon types
CyberGlove18 sensors22 sensors
5DT Glove 5 sensors16 sensors
Require calibrationtime-consuming processresults often not perfect
Sensor readings do not correspond directly to joint angles requires nonlinear mappingparticularly difficult: Thumb rotation
Data Gloves
Immersion Cyberglove II, 22 sensors
5DT Data Glove, 16 sensors
Prof. B. Jung Virtuelle Realität TU Freiberg
Mattel / Nintendo Power Glove (1989)
Image: wikipedia
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Prof. B. Jung Virtuelle Realität TU Freiberg
Optical Finger Tracking
Extension of motion tracking
accurate finger tip positionsreliable calculation of joint angles
simple calibration
line-of-sight issuesparticularly tricky: bimanual interactionmore cameras help
ART, www.ar-tracking.de
PTI, www.ptiphoenix.com
Prof. B. Jung Virtuelle Realität TU Freiberg
Continuous and discrete inputExamples
Button device + trackerFlex & PinchRing mouseLCD tabletCubic MouseSpaceballTracked PDA
Hybrid devices
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Prof. B. Jung Virtuelle Realität TU Freiberg
Buttons + Joystick + 6 DOF Tracking
Tracked Wands
Prof. B. Jung Virtuelle Realität TU Freiberg
Space MouseRing Mouse (pictured)Fly Mouse(pictured)
Mouse Type Devices
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Prof. B. Jung Virtuelle Realität TU Freiberg
SpaceballSpaceMouseSpaceOrb
Potentially tracked
SpaceNavigator
Stationary Devices
Prof. B. Jung Virtuelle Realität TU Freiberg
3Dconnection SpacePilot
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Prof. B. Jung Virtuelle Realität TU Freiberg
The Cubic Mouse
Fraunhofer IMK, Bernd Fröhlich & John Plate
Prof. B. Jung Virtuelle Realität TU Freiberg
Cubic Mouse
First 12 DOF input deviceTracks position and rotation of rods using potentiometers
Other shapes andimplementationspossible
Mini Cubic Mouse…
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Prof. B. Jung Virtuelle Realität TU Freiberg
Hinkley et al., 1994
Props
A physical object used to represent some manipulableobject in a virtual worldThe physical properties (shape, weight, texture, center of gravity, solidity) give a limited amount of haptic feedback, and often suggest how the device is used (e.g. putter) Real nature of props allows user to easily manipulate the object (e.g. hand it to another user).
Head propCar prop…
Prof. B. Jung Virtuelle Realität TU Freiberg
Tracking & interaction with handheld devices
tracked PDA
tracked stylusbuttons + stylus + 6DOF trackingtablet PC
Object selection (left) and manipulation (right)
work by Stefan Conrad, 2007
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Prof. B. Jung Virtuelle Realität TU Freiberg
Platforms
Larger physical structures used to interface with virtual worlds (the place where the user sits or stands) Can themselves represent some portion of the virtual world Can be generic or specific Several common platform types
Prof. B. Jung Virtuelle Realität TU Freiberg
Ring Platform
Generic Typically used with head-based displaysTypically has a waist-high rail surrounding the participant Often used with handheld props
Ascension Spacepad
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Prof. B. Jung Virtuelle Realität TU Freiberg
Kiosk Platform
Booth-like structure the user stands/sits at (like an arcade machine) Generally has physical controls mounted on it Often designed to be easily relocatable
Prof. B. Jung Virtuelle Realität TU Freiberg
Ambulatory platforms
Treadmill or stair-stepping machine Designed to provide realistic travel through the virtual world Physical exertion through leg motion gives proprioceptic feedback
www.virtusphere.com
Onmidirectional Platformwww.vsd.bz
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Prof. B. Jung Virtuelle Realität TU Freiberg
Vehicle platforms
Designed to seem as though you are riding in the cockpit of some craft Realistic controls panels are provided Large flight simulators are a familiar example Often used in theme-park VR systems
Prof. B. Jung Virtuelle Realität TU Freiberg
Input devices with Haptics
cyberglove with haptics
Haptic Workstation
Vibro-tactile feedback
All pictures: www.immersion.com
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Prof. B. Jung Virtuelle Realität TU Freiberg
www.measurand.com
Other input devices – Shape Tape
Prof. B. Jung Virtuelle Realität TU Freiberg
Other input devices – Position Tracking for minimal invasive surgery
Ascension 3D Guidance™ Tracker
"3D Guidance tracks the position and orientation of one or more tiny sensors, enabling real-time guidance of medical instruments for minimally invasive, image-guided procedures. Sensors, ranging in diameter from 1.8 mm to 0.3 mm, are typically embedded in the distal tip of catheters, scopes and probes. Measurements are unaffected when used in close proximity to intravascular ultrasound arrays."www.ascension-tech.com
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Prof. B. Jung Virtuelle Realität TU Freiberg
Other input devices –Neural (muscular) tracking methods
Means of sensing body part movement relative to other body parts(e.g. curling the hand into a fist). Has not been explored to a large degree in VR systems
Prof. B. Jung Virtuelle Realität TU Freiberg
Audio Input - Speech Recognition
Speech is a natural means of communicating information Can complement other modes of interactionmulti-modal interaction
How does computer know you're talking to it? push-to-talk name-to-talk look-to-talk
Issues to considercontinuous vs. one-time recognitionchoice and placement of microphonetraining vs. no traininghandling of false recognitionsurrounding noise interference
Not good when speaking can interfere with other operations Very good when hands are occupied with other tasks
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