it's not more easy with Goxel?
http://guillaumechereau.github.io/goxel/

Magicavoxel-->Goxel

or even if you want only render you have the free Simlab Composer Lite (works with any 3D format files! :)
who has a Voxel function! :) (Maxi 1920*1040) (you can only save in proprietary format! )