Unreal’s shading model has always been pretty good compared to anything else on out there when it comes to game engines, so I would be surprised if they got this wrong specifically on the landscapes. So first, I’ve made a flat landscape and a simple mesh plane and aligned them next to each other with no gap. Then I’ve put a fully rough material on it and captured a screenshot:
Next, I’ve introduced PBR texture set, some classic random megascans:
And yes, it indeed does look a bit slimey at the distance, not like a rough dry grass. But here’s what happens when I turn of mip mapping for all the maps:
This is the actual roughness I’d expect to see.
This is the ages old problem of game engine texture filtering not being anywhere near the quality of the texture filtering of offline renderers. But handling mip mapping imprecision at distance by introducing some weird roughness bias parameter specifically for landscape use would not be a fortunate solution for this I am afraid.
Anyway, it does not make sense to conflate it with Unity’s bug of handling roughness of landscape materials differently depending on gamma space. Unity has special shader for landscape which can’t be used for static meshes and vice versa. This shader had probably some hard coded gamma math for textures which did not properly updated when the switch between linear and sRGB space was added to Unity. It’s definitely not the same issue, or even similar.
What CryEngine folks talk about could be more related to that. I myself have encountered this problem too, so I too would like to see it solved. But at the same time, I’d like to avoid attributing the issue to factors which are not responsible for it.