Hi all,
I’ve been experiencing a strange issue in 5.1.1 with the ClearCoat shader. It looks like with Metallic=1, Roughness value=0 or close to 0 renders the surface completely black.
Below is comparison between 5.0.3 and 5.1.1, in both: GI an Reflections are set to Lumen, HWRT enabled, Nanite enabled on all geometry, Strata Materials disabled.
Disabling Nanite does not affect this, adding CCBottomNormal does not affect this.
Is this related to the recent introduction of Strata Materials?
It could be, they made a lot of shader changes in the 5.1 version of the engine. I suggest reporting this as a bug to get a response if this is intended. Thanks for highlighting.
Based on some feedback I got on UDN, this is indeed a Lumen issue in 5.1 and has been fixed in 5.2.
Based on a quick rnd of mine, a temporary solution to this problem is to set:
r.Lumen.Reflections.MaxRoughnessToTrace 0
It’s not great, clearly affects the rest of the rendering pipeline but does the job …
See the comparison below:
This bug is still present for me in the latest 5.3.2
Version: 5.3.2-29314046+++UE5+Release-5.3
The underlying surface reflections (not the top clearcoat) only display simple Phong highlights and blurry screenspace reflections (even with the roughness at 0) but no Lumen reflections.
The material editor preview scene appears correct because it doesn’t seem to use Lumen reflections. Switching to old UE4 style reflection probes makes it display ‘correctly’ like the material preview, but obviously changing a project’s entire reflection system to discard Lumen just for proper clearcoat rendering isn’t a real solution.
I tried the CVAR mentioned above, but it makes no difference.
