3D plot – Part 3
Continuing with our 3D graphs, we'll demonstrate the
use of the function '
sphere'. We are
going to draw a unit sphere centered at the origin and
generated by matrices
x,
y
and
z, of size 31 x 31 each.
Just as an exercise, we also
add a straight line
going from the center of the sphere to one of the corners in
the figure (within the
same 3D plot). This
is important to note the fact that we can add several
shapes to the figure, by using the instruction '
hold on '. We'll also
use functions to label the plot and will see how we can use
two coordinates to find more elements of the line
containing them.
Example:
We plot a
transparent sphere
using appropriate commands. We add a line from the center of
the sphere to one corner of the containing box. We
demonstrate the use of the instruction '
axis' with the
parameter ' square'.
% cleans the workspace
clc; clear; close all
% returns the coordinates of a sphere in three
% matrices that are (n+1)by(n+1) in size
[x, y, z] = sphere(30);
plot3(x,y,z)
% keeps the proportions in place and writes appropriate
info.
axis('square')
title('Transparent Sphere')
xlabel('x axis')
ylabel('y axis')
zlabel('z axis')
% keeps the above sphere in order to superimpose a
line
hold on
% the line goes from (1, 1, 1) to (0, 0, 0)
a = 1 : .1 : 0;
b = 1 : .1 : 0;
c = b;
plot3(a, b, c)
% draws the sphere in another format and in another
figure
% see what happens if we don't use the axis('square')
instruction
figure
mesh(x,y,z)
hold on
plot3(a, b, c)
And the resulting figures are:

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