3-D Visualization |
Parametric Surfaces
The functions that draw surfaces can take two additional vector or matrix arguments to describe surfaces with specific x and y data. If Z
is an m-by-n matrix, x
is an n-vector, and y
is an m-vector, then
describes a mesh surface with vertices having color C(i,j)
and located at the points
where x
corresponds to the columns of Z
and y
to its rows.
More generally, if X,
Y,
Z
, and C
are matrices of the same dimensions, then
describes a mesh surface with vertices having color C(i,j)
and located at the points
This example uses spherical coordinates to draw a sphere and color it with the pattern of pluses and minuses in a Hadamard matrix, an orthogonal matrix used in signal processing coding theory. The vectors theta
and phi
are in the range -
theta
and -
/2
phi
/2
. Because theta
is a row vector and phi
is a column vector, the multiplications that produce the matrices X
, Y
, and Z
are vector outer products.
k = 5; n = 2^k-1; theta = pi*
(-n:2:n)/n; phi = (pi/2)*
(-n:2:n)'/n; X = cos(phi)*
cos(theta); Y = cos(phi)*
sin(theta); Z = sin(phi)*
ones(size(theta)); colormap([0 0 0;1 1 1]) C = hadamard(2^k); surf(X,Y,Z,C) axis square
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