The problem is that i can’t do this myself without spending weeks or so reading books about how all of this works.
There don’t appear to be too many tutorials on how to create these effects, which may be further complicated by the fact that jME3 uses specific variable names (not that i know what they are supposed to represent) - https://docs.jmonkeyengine.org/advanced/jme3_shaders.html
The closest thing i found to anyone else having implemented fog shaders (still as a post process effect) in jME3 is this thread, the code in which seemed to be bugged (and after fixing it, it still used the same distance calculation approach) - https://hub.jmonkeyengine.org/t/glsl-implementation-of-fog-filter-linear-exp2-camera-to-distance-exp2-distance-to-infinity/23546/3
Bottom line, i can’t do it myself and have no idea where to start, therefore i decided to ask the community before giving up. I’m not really concerned about how it looks, i just need to make the limited rendering distance. That is all.