Graphics Programs Reference

In-Depth Information

The
patch
function has automatically joined the first and last points,

which we do not want to do. We can get rid of that line by setting the

final colour of the
FaceVertexCData
matrix to be
NaN
:

>> fvc(20,:) = NaN

fvc =

0

0.5000

0.4000

0.0526

0.52630.4000

[...]

0.8947 0.9474 0.4000

0.9474 0.9737 0.4000

NaN NaN NaN

>> set(h,'facevertexcdata',fvc)

As for most other instances of plotting
NaN
s, matlab handles not-a-

number elements by leaving them out. Our final plot of the cable omits

the points:

>> set(h,'marker','none')

Example: Coloured Cylinder
Suppose a cylindrical section of pipe

is heated and that it develops a temperature distribution such that the

temperature anywhere on its surface depends on the distance from the

point of heating. We will use a single call to the patch command to

draw the cylinder and display the temperature coded as different colours

on the cylinder's surface. We define the cylinder by defining the two

rings at its ends. We will use the vertex-and-faces method of spec-

ifying the patch, and num-

ber the vertices according to

the scheme shown in this dia-

gram. The vertices at the

bottom are numbered from 1

to
N
; the vertices at the top

are numbered from
N
+1 to

2
N
. The first face will be

formed by joining vertices 1,

N
+1,
N
+ 2 and 2. The

second face will be formed by

joining vertices 2,
N
+2,
N
+3

and 3; and so on. The final

face will be formed by joining vertices
N
,2
N
,
N
+ 1 and 1.
N
is equal

to 20 in the diagram shown here. We start by defining the
x
,
y
, and
z

coordinates that we need: