Spatiotemporal Information Processing

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14 Νοε 2013 (πριν από 3 χρόνια και 8 μήνες)

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Spatiotemporal
Information Processing

No.2

3 components of Virtual Reality
-
1

Sensing 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” is

J.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 :


1
st

: z
-
axis, α[degree]


2
nd

: y
-
axis, β[degree]


3
rd

: x
-
axis, γ[degree]



in the right figure

Sensing System : Euler angle























































Z
Y
X
z
y
x
1
0
0
0
cos
sin
0
sin
cos
cos
0
sin
0
1
0
sin
0
cos
cos
sin
0
sin
cos
0
0
0
1












(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 voltage

V=f (x,y,z,α,β,γ)


depends on distance from


transmitter and angle of receiver coil


(amount of flux linkage)

Orthogonal coil

V=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)

Sensing system : Tracker


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

Sensing system : Tracker

Sensing system : Tracker


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)

Tracker

2 transmitter

Receiver (fixed)

Receive US

Calculation

of distance

A transmitter is on the arc

A

B

A transmitter is on the cross point of 2 arcs.

Measurement of B transmitter by the same matter

Angle of the Tracker can be detected

Sensing system : Tracker

Tracker 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

Sensing system : Tracker

Tracker by ultrasound


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

Sensing system : Tracker

Tracker by ultrasound


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

Sensing system : Tracker

Tracker by ultrasound


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 : Tracker

Tracker 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

Sensing system : Tracker

Tracker by Optics


HoloStage, Immersive Virtual
Environment in Tokai University

Sensing system : Tracker

Tracker by Optics

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 device

basic 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 device

example 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 device

example 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 device

example of conductive ink type