Spatiotemporal Information Processing No.2 3 components of Virtual Reality-1 Sensing System

Spatiotemporal Information ProcessingNo.23 components of Virtual Reality-1Sensing System

Kazuhiko HAMAMOTO

Dept. of Information Media Technology,

School of Information and Telecommunication Eng.,

Tokai University, Japan

Today’s Contents

Virtual Reality and its 3 components (review)

Sensing System Tracker

Electromagnetic induction method Ultrasound method Optical method

Data Glove

Virtual Reality (review)

A computer will be able to process spatiotemporal information in next generation

To access the information, the computer will use human sense Ordinary behavior of person is also used as interface to

computer.

The human interface is “Virtual Reality”

Definition of “Virtual Reality” (review)

What is not actual, but has the same essence as actual thing

The world where we can access by the five senses and human behavior can be used as human interface directly

First proponent of “Virtual Reality” isJ.Lanier, USA, in 1987

3 elements of Virtual Reality (review) 3D Environment

3D virtual space is “natural” for human senses.

Real-Time Interaction Real time response of computer to action of

person Autonomy

Virtual space exists even if people (user) doesn’t exist,

Virtual space exists not only as human interface but independent of user.

Sensing system Detection of motion (head, eyeball, trunk, upper

limbs and lower limbs) in real 3D space and input to computer

Simulation system Creation of virtual space, and calculation of motion

of virtual objects and real-virtual matching

Display system (Realistic display) Display of not only visual but aural, tactile and

olfactory information, and stimulus of sense organs

3 components for Virtual Reality (review)

The relationship among 3 components (review)

Person

real space virtual space

Simulation system

Display system

Sensing system

computer

Sensing system What is done? and Where is it done? Measurement of Where

Coordinates and direction in 3D space 6 Degree Of Freedom : 6DOF

Coordinates 　 : x, y, z Direction : Euler angle (yaw, pitch, roll) “Tracker”

Measurement of What Form of hand or body and their action Creation and display of their CG after the measurement Input of the intention of operating object

Sensing system : Euler angle

Definition of the order of axis rotation

“yaw, pitch, roll” means : 1st : z-axis, α[degree] 2nd : y-axis, β[degree] 3rd : x-axis, γ[degree]

in the right figure

Sensing System : Euler angle

Z

Y

X

z

y

x

100

0cossin

0sincos

cos0sin

010

sin0cos

cossin0

sincos0

001

(X,Y,Z) ： World coordinate system(x,y,z) ： Local coordinate system

Required condition of Tracker

Measurement of coordinates (x,y,z) and direction (yaw, pitch, roll), total 6DOF

6DOF information can be measured in real time The sampling rate is enough for representation of

user’s natural action The precision is less than one of sense of organ The range where Tracker can measure 6DOF can

cover the range of user’s action Tracker doesn’t restrict user’s action and it should be

free from environment

Sensing system : Tracker Tracker by electromagnetic induction

Use of electromagnetic induction 3 coils intersect perpendicularly each other Transmitter (fixed)

Generation of changing Magnetic flux Receiver (moving object)

Change of Linkage flux -> induced current in each of coils

Magnitude of induced currents is determined by position (x,y,z) and direction (pitch,yaw,roll) of the receiver.

6DOF of the receiver (moving object) can be detected by the induced currents.

Transmitter coil（ fixed in the space ）

Receiver coil(x,y,z,α,β,γ)

Generation and change of

Electromagnetic field

Induced voltageV=f (x,y,z,α,β,γ)　 depends on distance from transmitter and angle of receiver coil (amount of flux linkage)

Orthogonal coilV=f (x,y,z,α,β,γ)V=f (x,y,z,α,β,γ)

9 equation, 6 unknown information

Sensing system : Tracker

Transmitter(orthogonal　

coil)

Receiver(orthogonal　

coil)

Magnetic　field

detector

drive　circuit

Control　unit

Output　of　6DOF　of　receiver　(X、 Y 、 Z 、 Roll、 Yaw、 Pitch)


Advantages High precision

Coordinate : a few [mm], Angle : less than 1[deg] Small size and light weight Not suffer from physical obstacles

Weak points Narrow range of measurement, which depends on the size

of transmitter Suffer from magnetic material, for example, a desk made by

steel More the number of receiver is, less the sampling rate

becomes



3SPACE SYSTEM (POLHEMUS Inc.)

ISOTRAKII

Precision position 　 2.4 [mm] angle 0.75 [degree]

Area hemisphere whose radius is

76 [cm]

Data rate 30pts/s (2receiver)

Tracker2 transmitter

Receiver (fixed)

Receive USCalculationof distance

A transmitter is on the arc

A

BA transmitter is on the cross point of 2 arcs.

Measurement of B transmitter by the same matter

Angle of the Tracker can be detected

The distance is used as a radius

Sensing system : TrackerTracker by ultrasound

6DOF measurement by 3 transmitters and 3 receivers

Advantages Easy for measurement Not suffer from magnetic materials

Weak points Error by a change of sound velocity Suffer from the reflection and physical obstacles


Ivan Sutherland’s method 3 transmitter on user’s helmet

37, 38.6, 40.2kHz 4 receivers at each corner of the ceiling Continuous USs are transmitted, and

separated after the measurement. 12 patterns of phase shifts between

transmitted USs and received USs can be used for position detection


InterSense, Inc. 　 IS-900 The wide range of tracking 3m×3m ～ 15m×15m The Precision

coordinate 　 4mm angle 　 0.2 ～ 0.4

[degree] The size of sensor

3cm ～ 4cm Data rate 　 180Hz


Markers emit by infrared rays and the markers are taken by high speed camera

Multiple camera and transmittance of infrared rays

High speed and high precision of measurement (6DOF in real time) can be realized

No restriction for user No limitation of the number of marker

Sensing system : TrackerTracker by Optics

Vicon Maximum 16million pixels ， 10-bit gray scale Maximum shutter speed 　 2000FPS Maximum motion processing speed 120FPS A small marker can cover the wide range and measure the

information in detailed Resolution less than 5mm in practical case

http://crescentinc.co.jp/vicon


HoloStage, Immersive Virtual Environment in Tokai University


Sensing system : glove device

Input of user’s intention of manipulation of computer (virtual space manipulation)

Keyboard and mouse are not enough. Data glove

Input of motion of hand and finger Every joint has a sensor. The sensor measures bent angle. Precision is 0.5 [degree]. The form of hand is prepared in CG.

Attach a sensor to hand and finger, their deformation are measured Optical fiber method

The change of transmittance by the bent angle

VPL Inc ， DataGlove, 1987 Conductive ink with cloth method

The change of resistance by a bend of finger Virtual Technologies Inc ， CyberGlove

Sensing system : glove devicebasic principles

VPL Inc, DataGlove 1987 2 fibers for one finger No.1 and No.2 joint of a finger

are measured. = 10DOF The shape of a fiber is “U”. LED -> fiber -> phototransistor Approximation of the action by

CG

Sensing system : glove deviceexample of optical type

Conductive ink Liquid with particle who

has conductivity, for example, carbon

The resistance depends on the length of a sensor.

The length of a sensor depends on the bent angle.

Short = low resistance

Long = high resistance

The bent angle sensor by conductive ink

Sensing system : glove deviceexample of conductive ink type

Immersion Inc, CyberGlove The number of sensor ： 18 or 22

18 models 2 sensor for each fingers, the

root of thums, the bent angle and twist of wrist

22 models 18 models + 4 No.1 angles of

each finger precision ： 0.5 degree Refresh rate ： 149 record/s

Sensing system : glove deviceexample of conductive ink type

Documents

Spatiotemporal Information Processing No.2 3 components of Virtual Reality-1 Sensing System