How to generate random sphere packing and export in STL format?

Given a domain (say the unit cube in the 1st octant), I am trying to generate a random sphere packing (overlapping or non-overlapping - doesn't matter) in it using solidworks(inputs will be allowable range of radii and its distribution, and porosity) and then export the model as an STL file. It is very easy to do so for 1 sphere in solidworks but I can't seem to find any feature in solidworks where such a random pack can be generated. Any help regarding using some other software for this purpose is also appreciated.