how to generate image of spherical object ?

i need spherical object in 2d matrix image, i have an example

m=1000;
n=1000;
%object
[X,Y,Z]=peaks;
Z1=imresize(Z,[m,n]);
figure,imshow(Z1,[])

here image shows peaks in 3D and similarly i need a sphere.

[Adam]

Surely a sphere in a 2d matrix is just a circle?

Answer 1

[KSSV]

[X,Y,Z]=sphere;
surf(X,Y,Z) ;

doc sphere