How can I get a matrix of ellipsoid?

I want to have a matrix of ellipsoid, without using the matlab "ellipsoid" function, or other functions, because I need to work on the each 2d slice from the ellipsoid, so I better have a matrix representing the ellipsoid. It can be only 0 and 1 in value though. How can I generate this 3d matrix?

Can anyone help me? Thanks in advance!!

[Chen]

a possible resource: https://www.mathworks.com/matlabcentral/answers/58885-creating-a-spherical-matrix