The below code is meant to accompany the 3D Gaussian Convolution post. Note that the code is not generic and only calculates a 5x5x5 Gaussian on a set of 256x256 planes. It is very easy to modify to support other sizes and could even be templated. The Z convolution is not included in the code, but remember in this step you would need to do the final division.
As blogger doesn't seem to like keeping the format of code, please find it on GitHub https://github.com/Repmov/3D-Gaussian