Lumen ignores material roughness. Steps to reproduce:
-Open a new level, delete the directional light, switch the skylight to use a cubemap
-Make a new material, set it to translucent, forward shading, plug in any intense normal map
-Make it fully rough using a scalar parameter (value of 1)
-Duplicate the material, convert the scalar parameter into a constant with a value of 1
-Apply the two materials to two cubes
The one using the constant 1 will be fully rough, the parameter will ignore the roughness value when it comes to light coming from Lumen. Lumen reflections on the other hand seem to work and appear only with low roughness value. If you change the constant 1 to 0.99 then that one will be broken as well.
I have already submitted a bugreport, but wanted to share here as well in case someone bumps into this issue. I have spent half a day wondering how I managed to break it and basically dissected it down to atoms when it became obvious that it’s a bug.
