<s>
In	O
computing	O
,	O
3D	B-General_Concept
interaction	I-General_Concept
is	O
a	O
form	O
of	O
human-machine	O
interaction	O
where	O
users	O
are	O
able	O
to	O
move	O
and	O
perform	O
interaction	O
in	O
3D	O
space	O
.	O
</s>
<s>
The	O
3D	O
space	O
used	O
for	O
interaction	O
can	O
be	O
the	O
real	O
physical	O
space	O
,	O
a	O
virtual	B-Application
space	I-Application
representation	O
simulated	O
in	O
the	O
computer	O
,	O
or	O
a	O
combination	O
of	O
both	O
.	O
</s>
<s>
When	O
the	O
real	O
physical	O
space	O
is	O
used	O
for	O
data	O
input	O
,	O
the	O
human	O
interacts	O
with	O
the	O
machine	O
performing	O
actions	O
using	O
an	O
input	B-Device
device	I-Device
that	O
detects	B-Operating_System
the	I-Operating_System
3D	I-Operating_System
position	I-Operating_System
of	O
the	O
human	O
interaction	O
,	O
among	O
other	O
things	O
.	O
</s>
<s>
When	O
it	O
is	O
used	O
for	O
data	O
output	O
,	O
the	O
simulated	O
3D	O
virtual	O
scene	O
is	O
projected	O
onto	O
the	O
real	O
environment	O
through	O
one	O
output	B-Device
device	I-Device
.	O
</s>
<s>
The	O
principles	O
of	O
3D	B-General_Concept
interaction	I-General_Concept
are	O
applied	O
in	O
a	O
variety	O
of	O
domains	O
such	O
as	O
tourism	O
,	O
art	O
,	O
gaming	O
,	O
simulation	O
,	O
education	O
,	O
information	B-Application
visualization	I-Application
,	O
or	O
scientific	B-Application
visualization	I-Application
.	O
</s>
<s>
Research	O
in	O
3D	B-General_Concept
interaction	I-General_Concept
and	O
3D	O
display	O
began	O
in	O
the	O
1960s	O
,	O
pioneered	O
by	O
researchers	O
like	O
Ivan	O
Sutherland	O
,	O
Fred	O
Brooks	O
,	O
Bob	O
Sproull	O
,	O
Andrew	O
Ortony	O
and	O
Richard	O
Feldman	O
.	O
</s>
<s>
But	O
it	O
was	O
not	O
until	O
1962	O
when	O
Morton	O
Heilig	O
invented	O
the	O
Sensorama	B-General_Concept
simulator	O
.	O
</s>
<s>
It	O
provided	O
3D	O
video	O
feedback	O
,	O
as	O
well	O
motion	O
,	O
audio	O
,	O
and	O
feedbacks	O
to	O
produce	O
a	O
virtual	B-General_Concept
environment	I-General_Concept
.	O
</s>
<s>
He	O
created	O
a	O
head-mounted	O
display	O
that	O
produced	O
3D	O
virtual	B-General_Concept
environment	I-General_Concept
by	O
presenting	O
a	O
left	O
and	O
right	O
still	O
image	O
of	O
that	O
environment	O
.	O
</s>
<s>
Availability	O
of	O
technology	O
as	O
well	O
as	O
impractical	O
costs	O
held	O
back	O
the	O
development	O
and	O
application	O
of	O
virtual	B-Application
environments	I-Application
until	O
the	O
1980s	O
.	O
</s>
<s>
In	O
3D	B-General_Concept
interaction	I-General_Concept
,	O
users	O
carry	O
out	O
their	O
tasks	O
and	O
perform	O
functions	O
by	O
exchanging	O
information	O
with	O
computer	O
systems	O
in	O
3D	O
space	O
.	O
</s>
<s>
The	O
tasks	O
that	O
users	O
perform	O
have	O
been	O
classified	O
as	O
selection	B-General_Concept
and	O
manipulation	O
of	O
objects	O
in	O
virtual	B-Application
space	I-Application
,	O
navigation	O
,	O
and	O
system	O
control	O
.	O
</s>
<s>
Tasks	O
can	O
be	O
performed	O
in	O
virtual	B-Application
space	I-Application
through	O
interaction	B-Application
techniques	I-Application
and	O
by	O
utilizing	O
interaction	O
devices	O
.	O
</s>
<s>
3D	B-General_Concept
interaction	I-General_Concept
techniques	O
were	O
classified	O
according	O
to	O
the	O
task	O
group	O
it	O
supports	O
.	O
</s>
<s>
Techniques	O
that	O
support	O
object	O
selection	B-General_Concept
and	O
manipulation	O
are	O
labeled	O
selection	B-General_Concept
and	O
manipulation	O
techniques	O
.	O
</s>
<s>
Interfaces	O
associated	O
with	O
3D	B-General_Concept
interaction	I-General_Concept
are	O
called	O
3D	O
interfaces	O
.	O
</s>
<s>
Like	O
other	O
types	O
of	O
user	B-Application
interfaces	I-Application
,	O
it	O
involves	O
two-way	O
communication	O
between	O
users	O
and	O
system	O
,	O
but	O
allows	O
users	O
to	O
perform	O
action	O
in	O
3D	O
space	O
.	O
</s>
<s>
Input	B-Device
devices	I-Device
permit	O
the	O
users	O
to	O
give	O
directions	O
and	O
commands	O
to	O
the	O
system	O
,	O
while	O
output	B-Device
devices	I-Device
allow	O
the	O
machine	O
to	O
present	O
information	O
back	O
to	O
them	O
.	O
</s>
<s>
3D	O
interfaces	O
have	O
been	O
used	O
in	O
applications	O
that	O
feature	O
virtual	B-Application
environments	I-Application
,	O
and	O
augmented	B-General_Concept
and	O
mixed	B-General_Concept
realities	I-General_Concept
.	O
</s>
<s>
In	O
virtual	B-Application
environments	I-Application
,	O
users	O
may	O
interact	O
directly	O
with	O
the	O
environment	O
or	O
use	O
tools	O
with	O
specific	O
functionalities	O
to	O
do	O
so	O
.	O
</s>
<s>
3D	B-General_Concept
interaction	I-General_Concept
occurs	O
when	O
physical	O
tools	O
are	O
controlled	O
in	O
3D	O
spatial	O
context	O
to	O
control	O
a	O
corresponding	O
virtual	O
tool	O
.	O
</s>
<s>
Texture	O
,	O
sound	O
,	O
and	O
speech	O
can	O
all	O
be	O
used	O
to	O
augment	O
3D	B-General_Concept
interaction	I-General_Concept
.	O
</s>
<s>
Although	O
it	O
’s	O
a	O
natural	O
way	O
for	O
humans	O
to	O
move	O
around	O
in	O
a	O
three-dimensional	O
world	O
,	O
the	O
difficulty	O
exists	O
because	O
many	O
of	O
the	O
cues	O
present	O
in	O
real	O
environments	O
are	O
missing	O
from	O
virtual	B-Application
environments	I-Application
.	O
</s>
<s>
Also	O
,	O
even	O
though	O
scenes	O
in	O
virtual	B-Application
space	I-Application
appear	O
three-dimensional	O
,	O
they	O
are	O
still	O
displayed	O
on	O
a	O
2D	O
surface	O
so	O
some	O
inconsistencies	O
in	O
depth	O
perception	O
will	O
still	O
exist	O
.	O
</s>
<s>
User	B-Application
interfaces	I-Application
are	O
the	O
means	O
for	O
communication	O
between	O
users	O
and	O
systems	O
.	O
</s>
<s>
Using	O
3D	O
representations	O
is	O
not	O
enough	O
to	O
create	O
3D	B-General_Concept
interaction	I-General_Concept
.	O
</s>
<s>
To	O
that	O
effect	O
,	O
special	O
input	O
and	O
output	B-Device
devices	I-Device
have	O
been	O
developed	O
to	O
support	O
this	O
type	O
of	O
interaction	O
.	O
</s>
<s>
3D	B-General_Concept
user	I-General_Concept
interfaces	I-General_Concept
,	O
are	O
user	B-Application
interfaces	I-Application
where	O
3D	B-General_Concept
interaction	I-General_Concept
takes	O
place	O
,	O
this	O
means	O
that	O
the	O
user	O
's	O
tasks	O
occur	O
directly	O
within	O
a	O
three-dimensional	O
space	O
.	O
</s>
<s>
3D	B-General_Concept
user	I-General_Concept
interfaces	I-General_Concept
are	O
actually	O
physical	O
devices	O
that	O
communicate	O
the	O
user	O
and	O
the	O
system	O
with	O
the	O
minimum	O
delay	O
,	O
in	O
this	O
case	O
there	O
are	O
two	O
types	O
:	O
3D	B-General_Concept
User	I-General_Concept
Interface	I-General_Concept
Output	B-Device
Hardware	I-Device
and	O
3D	B-General_Concept
User	I-General_Concept
Interface	I-General_Concept
Input	B-Device
Hardware	I-Device
.	O
</s>
<s>
Output	B-Device
devices	I-Device
,	O
also	O
called	O
display	O
devices	O
,	O
allow	O
the	O
machine	O
to	O
provide	O
information	O
or	O
feedback	O
to	O
one	O
or	O
more	O
users	O
through	O
the	O
human	O
perceptual	O
system	O
.	O
</s>
<s>
The	O
main	O
types	O
of	O
displays	O
used	O
in	O
3D	B-General_Concept
user	I-General_Concept
interfaces	I-General_Concept
are	O
:	O
monitors	O
,	O
surround-screen	O
displays	O
,	O
workbenches	O
,	O
hemispherical	O
displays	O
,	O
head-mounted	O
displays	O
,	O
arm-mounted	O
displays	O
and	O
autostereoscopic	O
displays	O
.	O
</s>
<s>
Virtual	B-Device
reality	I-Device
headsets	I-Device
and	O
CAVEs	O
(	O
Cave	B-General_Concept
Automatic	I-General_Concept
Virtual	I-General_Concept
Environment	I-General_Concept
)	O
are	O
examples	O
of	O
a	O
fully	O
immersive	O
visual	O
display	O
,	O
where	O
the	O
user	O
can	O
see	O
only	O
the	O
virtual	O
world	O
and	O
not	O
the	O
real	O
world	O
.	O
</s>
<s>
These	O
hardware	O
devices	O
are	O
called	O
input	B-Device
devices	I-Device
and	O
their	O
aim	O
is	O
to	O
capture	O
and	O
interpret	O
the	O
actions	O
performed	O
by	O
the	O
user	O
.	O
</s>
<s>
Classical	O
interface	O
components	O
(	O
such	O
as	O
mouse	O
and	O
keyboards	B-Device
and	O
arguably	O
touchscreen	O
)	O
are	O
often	O
inappropriate	O
for	O
non	O
2D	O
interaction	O
needs	O
.	O
</s>
<s>
The	O
main	O
categories	O
of	O
these	O
devices	O
are	O
standard	O
(	O
desktop	O
)	O
input	B-Device
devices	I-Device
,	O
tracking	O
devices	O
,	O
control	O
devices	O
,	O
navigation	O
equipment	O
,	O
gesture	B-General_Concept
interfaces	I-General_Concept
,	O
3D	B-Device
mice	I-Device
,	O
and	O
brain	B-Application
–	I-Application
computer	I-Application
interfaces	I-Application
.	O
</s>
<s>
There	O
are	O
different	O
types	O
of	O
them	O
:	O
keyboards	B-Device
,	O
2D	B-Device
mice	I-Device
and	O
trackballs	O
,	O
pen-based	O
tablets	O
and	O
stylus	O
,	O
and	O
joysticks	B-Device
.	O
</s>
<s>
Nonetheless	O
,	O
many	O
studies	O
have	O
questioned	O
the	O
appropriateness	O
of	O
desktop	O
interface	O
components	O
for	O
3D	B-General_Concept
interaction	I-General_Concept
though	O
this	O
is	O
still	O
debated	O
.	O
</s>
<s>
3D	B-General_Concept
user	I-General_Concept
interaction	I-General_Concept
systems	O
are	O
based	O
primarily	O
on	O
motion	B-Application
tracking	I-Application
technologies	O
,	O
to	O
obtain	O
all	O
the	O
necessary	O
information	O
from	O
the	O
user	O
through	O
the	O
analysis	B-General_Concept
of	I-General_Concept
their	I-General_Concept
movements	I-General_Concept
or	I-General_Concept
gestures	I-General_Concept
,	O
these	O
technologies	O
are	O
called	O
,	O
tracking	O
technologies	O
.	O
</s>
<s>
Examples	O
of	O
trackers	O
include	O
motion	B-Application
trackers	I-Application
,	O
eye	B-General_Concept
trackers	I-General_Concept
,	O
and	O
data	B-General_Concept
gloves	I-General_Concept
.	O
</s>
<s>
In	O
the	O
case	O
of	O
navigation	O
devices	O
,	O
the	O
information	O
passed	O
on	O
to	O
the	O
machine	O
is	O
the	O
user	O
's	O
location	O
and	O
movements	O
in	O
virtual	B-Application
space	I-Application
.	O
</s>
<s>
Wired	B-General_Concept
gloves	I-General_Concept
and	O
bodysuits	O
allow	O
gestural	O
interaction	O
to	O
occur	O
.	O
</s>
<s>
For	O
the	O
full	O
development	O
of	O
a	O
3D	B-General_Concept
User	I-General_Concept
Interaction	I-General_Concept
system	O
,	O
is	O
required	O
to	O
have	O
access	O
to	O
a	O
few	O
basic	O
parameters	O
,	O
all	O
this	O
technology-based	O
system	O
should	O
know	O
,	O
or	O
at	O
least	O
partially	O
,	O
as	O
the	O
relative	O
position	O
of	O
the	O
user	O
,	O
the	O
absolute	O
position	O
,	O
angular	O
velocity	O
,	O
rotation	O
data	O
,	O
orientation	O
or	O
height	O
.	O
</s>
<s>
Inertial	O
tracking	O
systems	O
do	O
not	O
require	O
external	O
reference	O
such	O
as	O
those	O
based	O
on	O
movement	O
,	O
are	O
based	O
on	O
the	O
collection	O
of	O
data	O
using	O
accelerometers	O
,	O
gyroscopes	B-Application
,	O
or	O
video	O
cameras	O
,	O
without	O
a	O
fixed	O
reference	O
mandatory	O
,	O
in	O
the	O
majority	O
of	O
cases	O
,	O
the	O
main	O
problem	O
of	O
this	O
system	O
,	O
is	O
based	O
on	O
not	O
obtaining	O
the	O
absolute	O
position	O
,	O
since	O
not	O
part	O
of	O
any	O
pre-set	O
external	O
reference	O
point	O
so	O
it	O
always	O
gets	O
the	O
relative	O
position	O
of	O
the	O
user	O
,	O
aspect	O
that	O
causes	O
cumulative	O
errors	O
in	O
the	O
process	O
of	O
sampling	B-Algorithm
data	O
.	O
</s>
<s>
The	O
goal	O
to	O
achieve	O
in	O
a	O
3D	O
tracking	O
system	O
would	O
be	O
based	O
on	O
obtaining	O
a	O
system	O
of	O
6-DOF	O
able	O
to	O
get	O
absolute	O
positioning	O
and	O
precision	O
of	O
movement	O
and	O
orientation	O
,	O
with	O
a	O
precision	O
and	O
an	O
uncut	O
space	O
very	O
high	O
,	O
a	O
good	O
example	O
of	O
a	O
rough	O
situation	O
would	O
be	O
a	O
mobile	O
phone	O
,	O
since	O
it	O
has	O
all	O
the	O
motion	B-Application
capture	I-Application
sensors	O
and	O
also	O
GPS	O
tracking	O
of	O
latitude	O
,	O
but	O
currently	O
these	O
systems	O
are	O
not	O
so	O
accurate	O
to	O
capture	O
data	O
with	O
a	O
precision	O
of	O
centimeters	O
and	O
therefore	O
would	O
be	O
invalid	O
.	O
</s>
<s>
The	O
Wii	B-Device
Remote	I-Device
device	O
does	O
not	O
offer	O
a	O
technology	O
based	O
on	O
6-DOF	O
since	O
again	O
,	O
cannot	O
provide	O
absolute	O
position	O
,	O
in	O
contrast	O
,	O
is	O
equipped	O
with	O
a	O
multitude	O
of	O
sensors	O
,	O
which	O
convert	O
a	O
2D	O
device	O
in	O
a	O
great	O
tool	O
of	O
interaction	O
in	O
3D	O
environments	O
.	O
</s>
<s>
This	O
device	O
has	O
gyroscopes	B-Application
to	O
detect	O
rotation	O
of	O
the	O
user	O
,	O
accelerometers	O
ADXL3000	O
,	O
for	O
obtaining	O
speed	O
and	O
movement	O
of	O
the	O
hands	O
,	O
optical	O
sensors	O
for	O
determining	O
orientation	O
and	O
electronic	O
compasses	O
and	O
infra-red	O
devices	O
to	O
capture	O
the	O
position	O
.	O
</s>
<s>
The	O
Tango	B-Algorithm
Platform	I-Algorithm
is	O
an	O
augmented	B-General_Concept
reality	I-General_Concept
computing	O
platform	O
,	O
developed	O
and	O
authored	O
by	O
the	O
Advanced	O
Technology	O
and	O
Projects	O
(	O
ATAP	O
)	O
,	O
a	O
skunkworks	O
division	O
of	O
Google	O
.	O
</s>
<s>
It	O
uses	O
computer	O
vision	O
and	O
internal	O
sensors	O
(	O
like	O
gyroscopes	B-Application
)	O
to	O
enable	O
mobile	O
devices	O
,	O
such	O
as	O
smartphones	O
and	O
tablets	O
,	O
to	O
detect	O
their	O
position	O
relative	O
to	O
the	O
world	O
around	O
them	O
without	O
using	O
GPS	O
or	O
other	O
external	O
signals	O
.	O
</s>
<s>
The	O
Google	O
Tango	B-Algorithm
devices	O
can	O
be	O
seen	O
as	O
more	O
integrated	O
solutions	O
than	O
the	O
early	O
prototypes	O
combining	O
spatially-tracked	O
devices	O
with	O
touch-enabled-screens	O
for	O
3D	O
environments	O
.	O
</s>
<s>
The	O
Microsoft	B-Algorithm
Kinect	I-Algorithm
device	O
offers	O
us	O
a	O
different	O
motion	B-Application
capture	I-Application
technology	O
for	O
tracking	O
.	O
</s>
<s>
Instead	O
of	O
basing	O
its	O
operation	O
on	O
sensors	O
,	O
this	O
is	O
based	O
on	O
a	O
structured	B-Algorithm
light	I-Algorithm
scanner	I-Algorithm
,	O
located	O
in	O
a	O
bar	O
,	O
which	O
allows	O
tracking	O
of	O
the	O
entire	O
body	O
through	O
the	O
detection	O
of	O
about	O
20	O
spatial	O
points	O
,	O
of	O
which	O
3	O
different	O
degrees	O
of	O
freedom	O
are	O
measured	O
to	O
obtain	O
position	O
,	O
velocity	O
and	O
rotation	O
of	O
each	O
point	O
.	O
</s>
<s>
The	O
Leap	B-General_Concept
Motion	I-General_Concept
is	O
a	O
new	O
system	O
of	O
tracking	O
of	O
hands	O
,	O
designed	O
for	O
small	O
spaces	O
,	O
allowing	O
a	O
new	O
interaction	O
in	O
3D	O
environments	O
for	O
desktop	O
applications	O
,	O
so	O
it	O
offers	O
a	O
great	O
fluidity	O
when	O
browsing	O
through	O
three-dimensional	O
environments	O
in	O
a	O
realistic	O
way	O
.	O
</s>
<s>
3D	B-General_Concept
Interaction	I-General_Concept
Techniques	O
are	O
the	O
different	O
ways	O
that	O
the	O
user	O
can	O
interact	O
with	O
the	O
3D	O
virtual	B-General_Concept
environment	I-General_Concept
to	O
execute	O
different	O
kind	O
of	O
tasks	O
.	O
</s>
<s>
The	O
quality	O
of	O
these	O
techniques	O
has	O
a	O
profound	O
effect	O
on	O
the	O
quality	O
of	O
the	O
entire	O
3D	B-General_Concept
User	I-General_Concept
Interfaces	I-General_Concept
.	O
</s>
<s>
They	O
can	O
be	O
classified	O
into	O
three	O
different	O
groups	O
:	O
Navigation	O
,	O
Selection	B-General_Concept
and	O
manipulation	O
and	O
System	O
control	O
.	O
</s>
<s>
Wayfinding	O
refers	O
to	O
finding	O
and	O
setting	O
routes	O
to	O
get	O
to	O
a	O
travel	O
goal	O
within	O
the	O
virtual	B-General_Concept
environment	I-General_Concept
.	O
</s>
<s>
This	O
orientation	O
is	O
usually	O
handled	O
in	O
immersive	O
virtual	B-Application
environments	I-Application
by	O
head	B-Application
tracking	I-Application
.	O
</s>
<s>
Exists	O
five	O
types	O
of	O
travel	O
interaction	B-Application
techniques	I-Application
:	O
</s>
<s>
Physical	O
movement	O
:	O
uses	O
the	O
user	O
's	O
body	O
motion	O
to	O
move	O
through	O
the	O
virtual	B-General_Concept
environment	I-General_Concept
.	O
</s>
<s>
Is	O
an	O
appropriate	O
technique	O
when	O
is	O
required	O
an	O
augmented	B-General_Concept
perception	O
of	O
the	O
feeling	O
of	O
being	O
present	O
or	O
when	O
is	O
required	O
physical	O
effort	O
form	O
the	O
user	O
.	O
</s>
<s>
Manual	O
viewpoint	O
manipulation	O
:	O
the	O
user	O
's	O
hands	O
movements	O
determine	O
the	O
displacement	O
on	O
the	O
virtual	B-General_Concept
environment	I-General_Concept
.	O
</s>
<s>
The	O
user	O
may	O
draw	O
a	O
path	O
on	O
a	O
map	O
of	O
the	O
virtual	B-General_Concept
environment	I-General_Concept
to	O
plan	O
a	O
route	O
.	O
</s>
<s>
In	O
virtual	B-Application
space	I-Application
it	O
is	O
different	O
and	O
more	O
difficult	O
to	O
do	O
than	O
in	O
the	O
real	O
world	O
because	O
synthetic	O
environments	O
are	O
often	O
missing	O
perceptual	O
cues	O
and	O
movement	O
constraints	O
.	O
</s>
<s>
In	O
order	O
for	O
a	O
good	O
wayfinding	O
,	O
users	O
should	O
receive	O
wayfinding	O
supports	O
during	O
the	O
virtual	B-General_Concept
environment	I-General_Concept
travel	O
to	O
facilitate	O
it	O
because	O
of	O
the	O
constraints	O
from	O
the	O
virtual	O
world	O
.	O
</s>
<s>
Selection	B-General_Concept
and	O
Manipulation	O
techniques	O
for	O
3D	O
environments	O
must	O
accomplish	O
at	O
least	O
one	O
of	O
three	O
basic	O
tasks	O
:	O
object	O
selection	B-General_Concept
,	O
object	O
positioning	O
and	O
object	O
rotation	O
.	O
</s>
<s>
3D	O
widgets	O
can	O
be	O
used	O
to	O
put	O
controls	O
on	O
objects	O
:	O
these	O
are	O
usually	O
called	O
3D	O
Gizmos	O
or	O
Manipulators	O
(	O
a	O
good	O
example	O
are	O
from	O
Blender	B-Application
)	O
.	O
</s>
<s>
Another	O
technique	O
to	O
select	O
and	O
manipulate	O
objects	O
in	O
3D	O
virtual	B-Application
spaces	I-Application
consists	O
in	O
pointing	O
at	O
objects	O
using	O
a	O
virtual-ray	O
emanating	O
from	O
the	O
virtual	O
hand	O
.	O
</s>
<s>
3D	O
Manipulations	O
occurs	O
before	O
a	O
selection	B-General_Concept
task	O
(	O
in	O
order	O
to	O
visually	O
identify	O
a	O
3D	O
selection	B-General_Concept
target	O
)	O
and	O
after	O
a	O
selection	B-General_Concept
has	O
occurred	O
,	O
to	O
manipulate	O
the	O
selected	O
object	O
.	O
</s>
<s>
It	O
is	O
the	O
basis	O
of	O
many	O
3D	O
software	O
(	O
such	O
as	O
Blender	B-Application
,	O
Autodesk	O
,	O
VTK	O
)	O
which	O
are	O
widely	O
used	O
.	O
</s>
<s>
These	O
software	O
,	O
available	O
mostly	O
on	O
computers	O
,	O
are	O
thus	O
almost	O
always	O
combined	O
with	O
a	O
mouse	O
and	O
keyboard	B-Device
.	O
</s>
<s>
With	O
the	O
recent	O
avent	O
of	O
multi-touch	O
enabled	O
smartphones	O
and	O
tablets	O
,	O
the	O
interaction	O
mappings	O
of	O
these	O
software	O
have	O
been	O
adapted	O
to	O
multi-touch	O
(	O
which	O
offers	O
more	O
simultaneous	O
DOF	O
manipulations	O
than	O
a	O
mouse	O
and	O
keyboard	B-Device
)	O
.	O
</s>
<s>
The	O
command	O
sender	O
always	O
includes	O
the	O
selection	B-General_Concept
of	O
an	O
element	O
from	O
a	O
set	O
.	O
</s>
