Guys guys! I think i found something for Z fighting! Some genius (ErnieDingo) did something like this in unity and he did some explanation in the link.
I’m gonna quote his reply here:
"Having no background in the rendering pipeline for Unreal, I cant comment. But the technique you might be able to adapt.
Basically, you need to render your decals into a separate rendertarget, using the Z from the target scene (im assuming you are using deferred here) to do rough z testing. Basically, severe bias on the decal Z test (to avoid any Z fighting). What you really are trying to do is exclude decals that are genuinely obscured by geometry. This pass is all about approximation. when rendering the decals you can add extra stuff like masks etc, baking more information into the rendertarget as you like.
What this then gives you is a view of all visible decals in the scene. Now, on the final render pass, you need to sample from this rendertarget (shader resource of course), blending in the decal onto the terrain. What this does is, Z fighting is completely avoided at any distance.
Let me know if this helps. I’ve made a few posts on this, including a step by step process I went through to get to my result. You will need to trawl through late to mid 2016 to find it. I couldnt.
This one was also where I posted"
Can someone more able bodied and suited for implementing this feature follow up on this and have talk with this ErnieDingo dude?! He might be the holder of holy grail here but i wouldn’t know cause i’m not a programmer. I’m just a simpleton level designer.
(Click on blue G icon to use the link!)