Quote - > Quote - Should there, in a "valid" shader, only ever be one gammaed output...

Yes. Anything else and you're letting Poser add two values together and you're not gamma correcting the final combined color, which is what we're trying to do.

I was afraid you were going to say that. The issue I saw with what I was asking was: the CoE thing wouldn't / couldn't be done properly because you'd be entering values for Poser to pass on to the renderer in more than one location (channel)... but I failed to even think it was adding colours. Yikes! Hypercolours. Right inside PoserSurface...

So, I'm back to square one with my face / makeup shader. I had kinda come up with a solution, but it's been rendered (pun intentional) invalid. So, I am still unable to get any gloss to appear on the lips to any degree - if any gloss appears anywhere, it's on the whole face.

Bill, I'm not going to ask you how to incorporate that into my shader, because you're making a competitive commercial product which will do exactly that with considerable finesse and it would be unethical for me to expect any further help now.

I now know what I can't do - I can't create a separate set of nodes and anti-gamma - process - gamma and plug into Alt_specular or reflection_color or any of those alongside of my current shader. In other words, I can't use the common model of one set of nodes for diffuse colour and another set for specualr effects.  All that information needs to come from the alt_diffuse channel.

I've tried to sort out from PR3 what was plugging into what, because I could do glossy lips with it, but oh dear, quickly got lost.

Back to simple node tricks. There must be some way to do this! I'll see what I can come up with.

Monterey/Mint21.x/Win10 - Blender3.x - PP11.3(cm) - Musescore3.6.2

Wir sind gewohnt, daß die Menschen verhöhnen was sie nicht verstehen
[it is clear that humans have contempt for that which they do not understand] 

Metaphor of Chooks