Landscape Reflections - Being PBR is Not Enough.

[Maximum-Dev]

@Deathrey

Yep. But what makes you think that it is incorrect? I’d expect real world landscape to look more or less the same way, if such a featureless landscape could exist. In fact, you can find quite a few locations, exhibiting such specular on vista terrain in places such as Sahara or Aral Sea.

Besides macrosurface bleeding into microsurface, I see no issues with shading and those should not be dealt on the shading level.
It is not limited by your normals. Directional shadow plays pivotal role too. While ambient occlusion textures would mip down to averages and give you pretty good dampening on indirect specular in the distance, there is nothing like that in place for directional shadow. All those rocks, grains of sand, blades of grass and what not, they all cast shadow. And with distance, you should perceive average of shadowed and unshadowed areas, and thus, averaged specular. But in the engine, you are getting full, because either shadows are disabled at such distance or even if they are not, they still would operate on a pretty smooth surface, not affecting your specular. In not so near future, it is likely to be addressed in realtime rendering. For now, gotta think about tech art wokarounds. And In this case, it is not the specular that should be adjusted, but something with shadow projection, (negative bias based based on roughness/distance/angle ? Added shadow based on roughness/angle/distance?) Should be something like that. But if you take away directional shadowing, I am convinced, that shading looks close enough to ground truth to call it correct.

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All your points are correct. Maybe I didn’t phrase it clear enough.
What engine does is it defines the shading for a surface. But no one is considering if that surface is supposed to be simulating a flat smooth surface or is intended to be simulating a very rough and noisy surface like terrain, which is why there should be some differences between a flat plastic plane and a flat terrain plane. We can call it workarounds, tricks, hacks or whatever it is. What I’m saying is, what do we do about it? or what “can” we do? Suggestions about shadowing are quite Epic Games level and not something any of us would want to do on our own.