I think the real issue here is to get the mesh material to blend into any landscape layers it is placed on.
But since there is no access to those data, a perfectly seamless transition is still limited to blend into 1 landscape layer and that's not exactly what's being done in Star Wars.
The only way I found around that was to copy all landscape layers inside the mesh material and use static switch parameters to choose which layer the mesh would blend into.
You will pay the cost for the one layer you switch to and not the rest of them, but the issue becomes having several material instances per mesh, which you will use to switch to different layers i.e:
MI_Rock_01_Snow MI_Rock_01_Mud MI_Rock_01_Sand
-(Depending on how many layers the mesh is intended to be placed upon).
Still, regardless of how seamless everything looks like, if lighting is not baked and the transition area isn't directly lit by a light source i.e is covered in shadows or is under an overcast sky, the intersecting areas are darkened by SSAO regardless of seamless normal transition. This can be visible on snow, sand, generally smooth materials.
That might be a feasible solution for some though.
Why not place the asset inside of an actor BP,shoot a ray or two out from the bottom or around the asset, find the terrain layer, save that to a float in material parameters and use that info as the blended texture. Then once everything looks good bake out the objects to get the perf back.
Hello from the future. For anyone still waiting for Olmo to reply with a blueprint, I offer you a similar solution (a range of solutions, even) after a bit more research. This tutorial comes from @Jack M. He now works for Quixel and put together this guide on numerous different methods of blending meshes into your terrain. Enjoy and rejoice!
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Here is the blog post walkthrough and the video tutorial.