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1.7.4.1 Surface Rendering
Example 1.15
Plot the sinc function whose equation is given by:

( x + )
2
2
sin y
z =
x + y 2
2
over the domain –8 < x < 8 and –8 < y < 8.

Solution: The implementation of the mesh rendering follows:

x=[-8:.1:8];
y=[-8:.1:8];
[X,Y]=meshgrid(x,y);
R=sqrt(X.^2+Y.^2)+eps;
Z=sin(R)./R;
mesh(X,Y,Z)

The variable eps is a tolerance number = 2 used for determining expres-
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sions near apparent singularities, to avoid numerical division by zero.
To generate a contour plot, we replace the last command in the above by:

contour(X,Y,Z,50) % The fourth argument specifies
% the number of contour lines to be shown

If we are interested only in a particular contour level, for example, the one
with elevation Z , we use the contour function with an option, as follows:
0

contour(X,Y,Z,[Z Z ])
o
o
Occasionally, we might be interested in displaying simultaneously the
mesh and contour rendering of a surface. This is possible through the use of
the command meshc. It is the same as the mesh command except that a
contour plot is drawn beneath the mesh.

Preparatory Activity: Look in your calculus book for some surfaces equations,
such as those of the hyperbolic paraboloid and the elliptic paraboloid and
others of your choice for the purpose of completing Pb. 1.16 of the next in-
class activity.

© 2001 by CRC Press LLC