Reflections and Roughness

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?

You could put a Fresnel node into the roughness slot to control it based off the angle of the surface.

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.

that “trick” crytek use is also used in UE4, and anywhere else that uses image based reflections.

it’s more likely that the math used to define roughness is different in cryengine and UE4 and they have different response curves.

I notice that this was happened when you use the Planar Reflection. When it doesn’t influence on your object everything works fine in rough value slot.