Hello!
It seems that the Ambient Cubemap functionality from the post-process volume affects the roughness value of all the objects of a scene, making it unusable in the latest version of UE4
You can see the problem in the image below in which the roughness value of the materials is 1 but it looks like its closer to 0.1 or something
Do you have any idea how to fix this?
Thanks !
I may have a solution
I came across an old forum in which a user made a custom Post process Ambient Cubemap through the use of a post process material
the problem is that it seems that the nodes in use work differently now
the second problem is that im not a shader guy and i really don’t know how to make a similar shader with the new nodes 
This should still work, what’s the specific issue you’re encountering?
Edit: You’ll need to use SceneTexture:PostProcessInput0 instead of SceneColor
Thanks @Arkiras
To expose the “level” input of your texture sampler you need to set it to use absolute mip level:
The return log2(x); node is HLSL typed into a custom node, you can find it by searching for “Custom”. Make sure you name the input to x:
Also some of your math constants are not set in the lower left portion of your graph, you’re multiplying by 1 and subtracting from 1. Your reference multiplies by 1.15 and subtracts from 3. Not sure what difference this will make honestly, these seem like magic numbers.
I assume you didn’t set these because you didn’t have the custom node so you couldn’t plug them in anyway, just make sure you don’t forget them.
Wow, thank you so much
So now my material identical to the example, same values and everything
The result is not perfect to say the least, the roughness is still weird, but at least now I have more control, I’m gonna mess with the constant to see if I can do something
