Clear Coat Bottom Normal Specular and Roughness response issues.

Development Asset Creation
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1

There are 2 problems that are noticeable with the second normal setup. Are these issues with our basic setup/material settings or are they issues within the shading model itself? I’ve attached a screenshot of a simple graph that reproduces the issue.

  1. The specular on the bottom normal disappears sooner than expected, when compared to the same normal map on a non-clear coat material. I was only able to keep the specular i was expecting there when the normal and bottom normals were the same or very similar but in that case the clear coat itself become very hard to notice.
  2. Also as roughness increases the normals appear to flatten out substantially in the shadowed side of the material the point where they can no longer be seen. Do the bottom normals not respond as strongly to indirect light as regular normals?

I’ll also add that this occurs whether we branch the shading model or not, and whether we use a normal map in the normals as well or not. My example writes a flat value into the normals to have a better sense of the clear coat itself which is similar to the actual textures that will be used by our artists in the real material (they are relatively flat/uniform). If the normals are too bumpy or too similar to the bottom normals we were finding it made the clear coat much less noticeable

Thanks for any insight here!

2

Steps to Reproduce

  1. Enable Clear Coat Second Normal in the project settings.
  2. Create a simple clear coat material that writes a normal map to the clear coat bottom normal and enables clear coat via the material pin. Also add parameters for the roughness and clear coat roughness
  3. Assign the material to a mesh in a level with a directional light.
  4. Rotate around the object and observe the speculars disappear when viewing the mesh from some angles (see the video)
  5. Increase the roughness and observe the bottom layer flattens out substantially in the shadow side. (See the screenshots with the different roughness/clearcoat parameter combinations)
3

Hi,

thanks for the repro steps. I started investigating the issue and found that a potential workaround for the specular issue is to connect a scalar parameter node to the anisotropy input and set it to e.g. 0.1 (based on this issue). However, this does not seem to solve the flattened normal map on the shadow side when the roughness increases. I’m still investigating that further and might file a bug report for it.

Can you please confirm if the proposed workaround for the specular issue works in your project?

Thanks,

Sam

4

Hi,

glad to hear the workaround for the specular issue does the job. I’m not sure if/when it will be fixed, but I will file a bug report and post the link here when it is made public.

Thanks,

Sam

5

Hi again,

the bug report was added to the public issue tracker at this link so you can track its progress.

Let me know if you have any further questions.

Thanks again,

sam

6

No problem. I will close the ticket.

Thanks

7

Hey! Thanks for the quick reply

I tried this in both my trivial repro case and in the real context, both of which are non-nanite meshes, and it does workaround the specular issue like you mentioned. Is that something that will be fixed at a later date?

8

Thanks! Since its tracked and we have a workaround for part of the issue we can consider this closed