contour3d draws level surfaces of a 3D function
f(x,y,z) on a 3D plot. The values of f(x,y,z) are to
be in the 3D hypermatrix f at the lattice grid points
defined by 1D or 3D matrices x, y and z.
INPUT If no arguments are supplied at all, then
contour3d draws a demonstration of nested spheres.
x,y,z: 1D or 3D matrices of coordinates of grid
points in space at which the function f is known.
f: 3D matrix of function values. Set any missing
f-values to %nan.
nf: if nf is simply a number of surfaces to draw,
then a colorbar is also drawn. However, if nf is
a vector of surface values, then no colorbar. You
can skip one or more colors in the current
colormap by specifying %nan at the corresponding
place in the vector nf of f values---useful for
superimposing iso-surface plots.
Any extra arguments to contour3d are passed on to
plot3d to empower you to set view, legend, and so on.
OUTPUT fvals: vector of set contour values.
Executing contour3d() draws an example.
