SECTION 4.6
327
Patterns
TABLE 4.35 Data values in a Coons patch mesh
EDGE FLAG
NEXT SET OF DATA VALUES
f
=
0
x
1
y
1
x
2
y
2
x
3
y
3
x
4
y
4
x
5
y
5
x
6
y
6
x
7
y
7
x
8
y
8
x
9
y
9
x
10
y
10
x
11
y
11
x
12
y
12
c
1
c
2
c
3
c
4
New patch; no implicit values
f
=
1
x
5
y
5
x
6
y
6
x
7
y
7
x
8
y
8
x
9
y
9
x
10
y
10
x
11
y
11
x
12
y
12
c
3
c
4
Implicit values:
(x
1
,
y
1
) = (x
4
,
y
4
) previous
(x
2
,
y
2
) = (x
5
,
y
5
) previous
(x
3
,
y
3
) = (x
6
,
y
6
) previous
(x
4
,
y
4
) = (x
7
,
y
7
) previous
c
1
=
c
2
previous
c
2
=
c
3
previous
f
=
2
x
5
y
5
x
6
y
6
x
7
y
7
x
8
y
8
x
9
y
9
x
10
y
10
x
11
y
11
x
12
y
12
c
3
c
4
Implicit values:
(x
1
,
y
1
) = (x
7
,
y
7
) previous
(x
2
,
y
2
) = (x
8
,
y
8
) previous
(x
3
,
y
3
) = (x
9
,
y
9
) previous
(x
4
,
y
4
) = (x
10
,
y
10
) previous
c
1
=
c
3
previous
c
2
=
c
4
previous
f
=
3
x
5
y
5
x
6
y
6
x
7
y
7
x
8
y
8
x
9
y
9
x
10
y
10
x
11
y
11
x
12
y
12
c
3
c
4
Implicit values:
(x
1
,
y
1
) = (x
10
,
y
10
) previous
(x
2
,
y
2
) = (x
11
,
y
11
) previous
(x
3
,
y
3
) = (x
12
,
y
12
) previous
(x
4
,
y
4
) = (x
1
,
y
1
) previous
c
1
=
c
4
previous
c
2
=
c
1
previous
Type 7 Shadings (Tensor-Product Patch Meshes)
Type 7 shadings (tensor-product patch meshes) are identical to type 6, except that
they are based on a bicubic tensor-product patch defined by 16 control points in-
stead of the 12 control points that define a Coons patch. The shading dictionaries
representing the two patch types differ only in the value of the
ShadingType
entry
and in the number of control points specified for each patch in the data stream.