Hi Luo,

Glad to hear that you found my piece useful. Thank you very much!

Regarding the first figure, it is created via a 3D surface generation routine. Here I've attached the code snippet. It's in Matlab, so I didn't put it in the notebook. Hope it can be helpful :)

% MATLAB code

clear

clc

N = [200 200]; % size in pixels of image

F = 4; % frequency-filter width

[X,Y] = ndgrid(1:N(1),1:N(2));

i = min(X-1,N(1)-X+1);

j = min(Y-1,N(2)-Y+1);

H = exp(-.5*(i.^2+j.^2)/F^2);

Z = real(ifft2(H.*fft2(randn(N))));

surf(X,Y,Z,'edgecolor','none');

axis off