Extension KHR_materials_specular

[atteneder]

Add support for extension KHR_materials_specular

This extension adds two parameters to the metallic-roughness material: specular and specularColor.

specular allows users to configure the strength of the specular reflection in the dielectric BRDF. A value of zero disables the specular reflection, resulting in a pure diffuse material. The metal BRDF is not affected by the parameter.

specularColor changes the F0 color of the specular reflection in the dielectric BRDF, allowing artists to use effects known from the specular-glossiness material (KHR_materials_pbrSpecularGlossiness) in the metallic-roughness material.

[aiaustin]

I wonder if this extension for the Unity glTF/glb importer has moved forward at all. The Blender glTF exporter (in Blender 4.* at least) does not seem to include an earlier way to tick a box to avoid using the PBR materials extensions.

[andybak]

According to https://docs.unity3d.com/Packages/com.unity.cloud.gltfast@6.1/manual/features.html this isn't even planned for the built-in pipeline. That seems an odd thing to omit.

[atteneder]

According to https://docs.unity3d.com/Packages/com.unity.cloud.gltfast@6.1/manual/features.html this isn't even planned for the built-in pipeline. That seems an odd thing to omit.

Thanks for raising that concern. The rationale behind this is the following:

The build-in glTF shader(s) are based on the built-in Standard shader. Those don't have the concept of specular factor or texture. That doesn't mean one could add them, but I shied away from that as it involves a considerable amount of work (think testing all platforms and graphics APIs). Combined with the uncertain support for built-in led me to decide to not prioritize bringing specular to built-in.

Of course that's not a decision that cannot be overthrown. Contributions are always welcome!

[YogurSligh]

For the urp pipeline, when will support for this material be provided?

[atteneder]

For the urp pipeline, when will support for this material be provided?

In short: No immediate plans. Hopefully we can focus on materials early next year.

Explanation:
Material features are mostly limited by shader variant explosion and workflow problems. I believe those should be resolved before adding more features on top of a unsteady foundation (which have to be maintained and supported across render pipelines!).

hth