Is possible add a shader or something to create metaballs or a sim of metaballs ?
Something like the portal 2 fluids.
Ehamloptiran had a fork of UE with MetaBalls. Alas it seems to be deleted at least I cannot see his fork anymore. You might ask him.
Yeah i know that project, but no idea about why don’t is merged with UE4 or why UE4 don’t have something similar.
Well two reasons. 1. Because its not a highly demanded feature and 2. Ehamloptirans version is not merged because it is still highly unoptimized, he even said this himself, and its got no integration into the particle systems, which is where it would be best implemented.
If you do get your hands on Ehamloptirans version, maybe you could clean it up, get it optimized, integrated into the Particle Systems and submit a pull request.
If you would like some advice on the approach Valve used in Portal 2, here is the documentation from GDC 2011 featuring the Metaballs.
Making and Using Non Standard Textures
http://www.valvesoftware.com/publications/2011/gdc_2011_grimes_nonstandard_textures.pdf
As mentioned, this would do best as a clean up/pull request and we would be interested to see this come forward!
Cheers,