3D data, back propagation of im2col

[qiqiing]

Hello, if I want to implement 3D data'im2col' and custom backpropagation based on your code, then how should I rewrite or change the'//equivalent implementation' part of'col2im_kernel' "coeff_d_col (depth)"coeff_h_col (height)" and "coeff_w_col (width)". Or you can explain why "coeff_h_col" is set like this and what is the meaning. I don’t understand this part of the code so much that I can’t rewrite the 3D code