I was under the impression that UE4 enabled the blurring of reflections as roughness increased. However, what i find is that as soon as roughness moves from 0.29 to 0.31 it just instantly drops off reflection intensity rather than blurring the reflection cubemap. This seems like bizarre behaviour for PBR mats.
Is there a way to make a material blur the reflection probes cubemap, similar to how marmoset works?
I tried a fresnel in the roughness. That works for the falloff, but doesnt appear to blur the reflection. Cry has a neat method using Mips in the reflection “while blurry reflections can be approximated efficiently by adjusting the MIP level during the lookup”
Also, why the sudden drop in reflection at 0.3? It seems like reflection drops by 50% at a change of 0.01 in roughness.