Best way on creating outdoor terrain with interior environments/buildings?

Hey all, I am making a small horror puzzle game which you can find more information on my blog via my signature link ( at the end of my posts. This is a senior thesis final school project that will take 1 year to complete. I finished my graybox level of the environment. It has multiple floors: main floor, 2nd floor, and basement floor. I want the player to be able to walk out and into the building, look out the window and see the environment. What is the best approach on making the terrain? I want to create a forest that makes the facility building hidden in. I realized that using the UE4 terrain tool will create a terrain that intersect with the building (main floor and basement floor) which is not ideal, correct me if I’m wrong. I also read about Solus Project UE4 free videos on making a modular terrain with a special UE4 material function that makes overlapping geometry textures merge together seamlessly. I am also interested in vertex painting as well and level streaming (not 100% what level streaming is).

So what is the best way to create my forest terrain? UE4 terrain tool? Manually modeling it in 3ds Max/Maya to create a modular kit?

Here’s some screenshots of the graybox environment level to give you a clearer idea of what I’m talking about and wanting to achieve.
Unlit view of Whole Facility outside:
Lit view far view of whole building showing multiple floors:
Main Floor to Basement Floor Stairway:
Main Floor Hall:
Wireframe Front View:
Basement Floor Hall:

Occlusion Culling might be a good thing to look at - I hear Umbra is a pretty excellent system for it for performance.

Landscapes done in Unreal Engine 4 pretty easily but imo the best way to do it would be to create the terrain and break it into chunks in a 3D modelling program and then import it in and split it with the “Levels” system to give a giant world feel with minimal performance hit.

Never heard of Occlusion Culling and never heard of Umbra. Can you give me resources on those topics? I’m would be interested in reading about them.

So you’re saying that I could build the landscape in UE4 using the terrain tool and texture/shade it as well then export it to a 3D modeling program and break it into multiple pieces (modular terrain kit)? or Just sculpt the terrain in UE4 then export it to a 3D modeling program, break it a part into a modular kit, then create a material for the textures? Add vertex painting and decals for mud and dead grass patches on the ground. I don’t want my terrain to have just one texture/material. I want a very realistic looking terrain. What do you mean by “Levels” system?

I thought of making the terrain in ZBrush and then creating a material with vertex painting in UE4. I would retypologize it in Zbrush and break it into different parts. Is that a good approach? Or would creating geometry from texture in 3ds Max/Maya and then making modular pieces out of it be better? I don’t know how I would paint with multiple materials though, I want grass, dead grass, mud, water puddles, and dirt.