KHR_materials_specular extension branch.

[UX3D-nopper]

No description provided.

[bhouston]

I've made some minor changes in this fork:
https://github.com/bhouston/glTF/tree/extensions/KHR_materials_specular/extensions/2.0/Khronos/KHR_materials_specular

This is just to better align with Autodesk and Dassault PBR Next analogs and also because artists have asked for this in order to achieve good looking materials.

[bhouston]

I just noticed that my proposal was nothing more than the existing competing specular proposal: #1719 I support that one over this one.

[kofi-de-com]

+1 for this extension. Aligns well with Blender's workflow.

[donmccurdy]

@kofi-de-com is there something specific about this proposal that you prefer over the version in #1719? Or do you mean a general +1 for either?

[kofi-de-com]

@donmccurdy it turned from a +1 for the specific proposal into a +1 for the extension in general.
At first glance it seemed easier to not have a specularColor feature. I've since then changed my mind and would suggest to move forward with #1719.
Background: As far as I can tell Blender does not properly support specular color tinting as suggested in #1719. It's specular tint value defaults to 0 (which behaves something like specularColorFactor(1, 1, 1)). If specular tint in Blender is set to 1, it looks like specularColorFactor(baseColor.r, baseColor.g, baseColor.b). However, these Blender material values could be converted at export time to work with #1719.

[UX3D-nopper]

closed in favor for #1719