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Slicing bezier surfaces
It
is
possible
to
split
a
bezier
surface
into
two
pieces.
It
helps
us
to
slice
a
surface
into
several
pieces
without
losing
the
original
shape.
In
that
way
we
are
able
to
delete
one
piece
of
several
slices
of
a
whole
surface.
-
code:js
-
function
splitBezier(t,
p0,
p1,
p2,
p3)
{
const
p4
=
lerp(t,
p0,
p1);
const
p5
=
lerp(t,
p1,
p2);
const
p6
=
lerp(t,
p2,
p3);
const
p7
=
lerp(t,
p4,
p5);
const
p8
=
lerp(t,
p5,
p6);
const
p9
=
lerp(t,
p7,
p8);
return
[
[{...p0},
p4,
p7,
p9],
[{...p9},
p8,
p6,
{...p3}]
];
}
This
is
a
javascript
code.
I
create
the
surface
editing
software
in
javascript.
The
function
lerp
is
identical
to
Python
one
that
I
mentioned
my
blog
post
before.
It
takes
the
t
value
between
0
and
1,
and
returns
two
bezier
curves,
one
is
the
half
that
splitted
at
t,
the
other
one
is
other
half.
Two
of
them
shapes
the
given
bezier
curve.
This
slices
a
curve
into
two
pieces.
So
I
slice
the
main
piece
until
it
is
one
piece
of
slices
I
want
while
I
create
another
surface
with
the
each
other
half.
-
code:js
-
let
sliceCurrent
=
4;
const
obj
=
{
"wide":
10,
"fall":
4,
"points":
[]
//
I
leave
it
empty
}
while
(sliceCurrent
>
1)
{
const
t
=
(obj["wide"]
/
sliceCurrent)
*
(sliceCurrent
-
1)
/
obj["wide"];
const
[halfa,
enda]
=
splitBezier(t,
obj.points[0],
obj.points[1],
obj.points[2],
obj.points[3]);
const
[halfb,
endb]
=
splitBezier(t,
obj.points[4],
obj.points[5],
obj.points[6],
obj.points[7]);
const
[halfc,
endc]
=
splitBezier(t,
obj.points[8],
obj.points[9],
obj.points[10],
obj.points[11]);
const
[halfd,
endd]
=
splitBezier(t,
obj.points[12],
obj.points[13],
obj.points[14],
obj.points[15]);
obj.points[0]
=
halfa[0];
obj.points[1]
=
halfa[1];
obj.points[2]
=
halfa[2];
obj.points[3]
=
halfa[3];
obj.points[4]
=
halfb[0];
obj.points[5]
=
halfb[1];
obj.points[6]
=
halfb[2];
obj.points[7]
=
halfb[3];
obj.points[8]
=
halfc[0];
obj.points[9]
=
halfc[1];
obj.points[10]
=
halfc[2];
obj.points[11]
=
halfc[3];
obj.points[12]
=
halfd[0];
obj.points[13]
=
halfd[1];
obj.points[14]
=
halfd[2];
obj.points[15]
=
halfd[3];
const
objNew
=
{
"id":
getNewId(),
"wide":
parseInt((1
-
t)
*
obj["wide"]),
"fall":
obj["fall"],
"type":
"plane",
"points":
[
enda[0],
enda[1],
enda[2],
enda[3],
endb[0],
endb[1],
endb[2],
endb[3],
endc[0],
endc[1],
endc[2],
endc[3],
endd[0],
endd[1],
endd[2],
endd[3]
],
};
draft.push(objNew);
obj["wide"]
*=
t;
sliceCurrentWide
-=
1;
}
obj["wide"]
=
int(obj["wide"])
This
slices
the
surface
horizontally
that
it's
segments
set
by
"wide"
parameter.
The
"fall"
is
for
the
vertical.
Same
method
must
be
applied
the
surface
if
it
needs
to
be
sliced
horizontally.
/screenshots/split.png:768
Good
luck
playing
with
that.
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