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MarwanGharib avatar image
MarwanGharib asked Boris_ answered

Clear coat material has some issues


Noticing some unexpected behaviours with clear coat shader :

1)Reflections rendering:

Clear coat reflections should not be coloured even if the underlying layer is metallic, see below image example :

clear coat with a rough metallic underlayer in clear skies scenario, works somewhat well:


Same material in cloudy weather scenario, notice the cloud reflections on the clearcoat layer are coloured in red.However, they should be reflected in their true colors so clouds should be white as the clear coat itself is not metallic.screenshot-2022-04-17-104211.png

Expected reflections behavior: below is an example of clear coat from other rendering engines. notice that reflection of underlying metallic layer are bluish , but clear coat reflections are not.


2)Red channels controls refraction index of clear coat , not clearcoat amount:

It is stated in the documentation that red channels controls clearcoat amount , however even if completely black clear coat is still applied and only IOR is affected .

while IOR control is very useful , prefer to have an additional method to control the actual presence of clear coat altogether.

suggestion: use the empty blue channel slot.

3)underlayer IOR affects clearcoat IOR:

if the under layer is non metallic , clear coat IOR follows the red channel input.

However it seems that having the underlayer metallic directly affects the IOR of the clear coat as well. Reflection on clear coat becomes more visible at perpendicular viewing angles.

Expected behavior: underlying layer should bear no impact on the clear coat's IOR.

both should be controlled separately and independently from each other.

4)Normal Maps are suppressed in clear coat shader:

I noticed that clearcoat doesn't translate normal details well and suppresses them unless the normal maps are very strong ,

I verified that it is not a reflection issues by looking at the dev mode's world normals view and verified absence of fine normal details.

I don't believe this should be the case.

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1 Answer

Boris_ avatar image
Boris_ answered

Hello @MarwanGharib ,

We opened an issue on our side regarding this shader.
However, no ETA for now.

Thanks for reporting this and for your feedback,



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