openCV Gaussian blur/smoothing of 3D Matrix/Histogram

Question

I have a (3D) Histogram which I like to apply Gaussian smoothing on:

cv::MatND Hist;

In the 1D and 2D cases I blur it via:

Answer 1

Try use separable kernels like shown here: http://www.programming-techniques.com/2013/03/gaussian-blurring-using-separable.html