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Radeon ProRender Discussion

tcheng
Adept I

PBR and Uber Shader Fresnel does not work correctly with Metalness Settings

Hi,

I had a long conversation on discord on how the PBR and Ubershader Fresnel seems to be incorrect.  The main problem is that the PBR shader with a Base color and Metalness connected does not produce any fresnel on the surface.  Both the dielectric and conductor materials seem to have no fresnel. Example Below. pastedImage_1.jpg

The same thing will happen if you setup a Uber Shader with the Reflection Mode set to Metalness. 

To illustrated how the PBR fresnel is suppose to look, I was able to setup two Uber Shader (one set to IOR 1.5, and the other Set to Metalness), and mask the metal with a Blend Material node.  It should look like this.

pastedImage_2.jpg

If you look at the seat/gas tank area, you can clearly see fresnel reflection, but it is missing if you use the PBR or Uber Shader set to metalness.

As a comparison, I've also attached a render from arnold PBR shader to show its fresnel.

pastedImage_3.jpg

The examples above are from 3DS Max, but I've seen the same behavior in Blender 2.8 with the Principled material.

f you have any questions, please let me know.  

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1 Reply
bsavery
Staff
Staff

Re: PBR and Uber Shader Fresnel does not work correctly with Metalness Settings

Can you create a simpler scene showing this?  And attach here.

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