solved The range of values for Material.specularPower ?

[JCPalmer]

From the version of the Blender exporter that deltaKosh wrote, the value for specular hardness was designated as the value for specularPower.

This has to change for processing Cycles nodes, without baking.  Ignoring the principled shader for now, this value now has an analog in the roughness value of a Glossy node.

Problem is this is a value from 0 to 1.  Also a value of 0 is shiniest while 1 is dullest.  The default value is 64. 

MakeHuman imports to Blender change based on the render currently assigned.  The eye mesh is the glossiest.  When using the internal render the hardness is 500.  Roughness in cycles is 0.

Does a range of 500 (0) to 64 (1) make sense?  There is very little in the way of documentation for this.

[V!nc3r]

My feeling (confirmed by the new inspector) is that the range is 0 - 128.

And about the convertion from Glossy BSDF roughness to Standard SpecularPower, here my guess:

• roughness = 0 give us specularPower = 0
• roughness = 1 give us specularPower = 128

[JCPalmer]

Thanks for the range.  I want as much as possible for what renders in Blender translates directly to either STD or PBR material.  Flipping the direction, does not seem like a good idea.

Also, for principled, should Specular Tint be serving the same purpose?

[V!nc3r]

I think keep using Roughness rather than the specular could be the right way even with the Principled.

[JCPalmer]

Maybe both ways for Principled.  I am not quite to Principled, but switching stuff there (or how it is interpreted by the 2 material classes) is clearly easier.  If you have the older mix shader rats nest, am not sure how much can be done.  Thinking the 2 material classes interpreting in different ways has obviously advantages.

I think, I understand where you are coming from.  If you are making your own materials with Principled, then you want to change between STD & PBR just using the world level, custom property, check box.  People will also be importing stuff into Blender from various formats.  If importers switch to principled, Makeuman included, they are going to use settings which look best for Blender. 

I do not want to hear a bunch of shit that it is not exporting right, when was imported to Blender by people with no clue about Blender.  Probably unrealistic, but I can dream.

I am almost done with non-principled, STD material processing, will use the principled topic when there.  This one is solved.

[V!nc3r]

I just see here that new gltf beta doc is available: https://gltf-blender-io-docs-gbueavkvns.now.sh/addons/io_gltf2

Maybe some tricks about principled use can be helpful or inspiring?

[JCPalmer]

Yeah, how they did emissive  was useful.  This is what will probably work for PBR here.  I can do complex, probably anyone of the image textures could be replaced with another type of texture.  That channel would be baked.  Still thinking of how to only bake certain channels leaving others, but big performance advantage if possible. Not sure the Separate RGB channel really does anything, unless BJS requires those 3 channels be in one texture.  My test will be if the urls match.

[JCPalmer]

Ok, after some more looking, selective channel baking is only (or only easily possible) for meshes which DO NOT have multiple materials.  Not ready to take on baking of partial meshes.  That enhancement is the next fool's problem.