My question is about shaders mostly. Is this possible to made an outline effect for ZDoom/GZDoom/Zandronum sourceports?
I mean things like this:

In Doom it should be like this (fake image):

Any ideas or suggestions? Thanks in advance.
I want to get this effect for any Doom wad, not only for my custom maps. It's stupid to ask such things if I wanted to do it to my custom maps -_-'You can also fake it by adding it to maps yourself, check out the levels in Action Doom 2: Urban Brawl.
Ok, let it be GZDoom only but where I can get such shader? Create it by myself? That is easier said than done.To answer your question though, I could imagine it might be possible with GLSL shaders that are possible with the new GZDoom builds, but ZDoom and Zandronum are probably out of the question without some extra program like ReShade acting on them.