<s>
In	O
computer	O
graphics	O
,	O
free-form	B-General_Concept
deformation	I-General_Concept
(	O
FFD	O
)	O
is	O
a	O
geometric	O
technique	O
used	O
to	O
model	O
simple	O
deformations	O
of	O
rigid	O
objects	O
.	O
</s>
<s>
It	O
is	O
based	O
on	O
the	O
idea	O
of	O
enclosing	O
an	O
object	O
within	O
a	O
cube	B-Application
or	O
another	O
hull	O
object	O
,	O
and	O
transforming	O
the	O
object	O
within	O
the	O
hull	O
as	O
the	O
hull	O
is	O
deformed	O
.	O
</s>
<s>
Deformation	O
of	O
the	O
hull	O
is	O
based	O
on	O
the	O
concept	O
of	O
so-called	O
hyper-patches	O
,	O
which	O
are	O
three-dimensional	O
analogs	O
of	O
parametric	O
curves	O
such	O
as	O
Bézier	O
curves	O
,	O
B-splines	B-Algorithm
,	O
or	O
NURBs	B-Algorithm
.	O
</s>
<s>
It	O
was	O
extended	O
by	O
Coquillart	O
to	O
a	O
technique	O
described	O
as	O
extended	O
free-form	B-General_Concept
deformation	I-General_Concept
,	O
which	O
refines	O
the	O
hull	O
object	O
by	O
introducing	O
additional	O
geometry	O
or	O
by	O
using	O
different	O
hull	O
objects	O
such	O
as	O
cylinders	O
and	O
prisms	O
.	O
</s>
<s>
Free-Form	B-General_Concept
Deformation	I-General_Concept
is	O
used	O
in	O
computer	O
graphics	O
for	O
solid	O
geometric	O
models	O
.	O
</s>
<s>
For	O
example	O
,	O
the	O
Lattice	O
Modifier	O
in	O
Blender	B-Application
(	O
software	O
)	O
.	O
</s>
<s>
It	O
is	O
used	O
in	O
the	O
image	B-Algorithm
registration	I-Algorithm
in	O
both	O
rigid	O
and	O
non-rigid	O
transformation	B-Algorithm
.	O
</s>
