Texture mask and constant value blending

Development Rendering
1

I’m having a hard time wrapping my brain around this, and its probably really simple…

I have a roughness and metallic map that is driven by a parameter. 1 gives the full values in those maps and 0 smooths out the model so there’s essentially 0 metallic and roughness, however, i would like 0 to just zero out those maps. I want a separate roughness and metallic parameter to drive those values by however much the maps are not.

Maybe a better way to put this would be that i want an override parameter for whatever the maps are not affecting?! 1 strength for the mask means 0 strength for the constant parameter. .25 strength for the mask means .75 strength for the parameter, etc. I’ve tried various combinations of multiplies, lerps and the blending modes (soft light, overlay) but they never quite work right. Its almost like i want them to be layers, with the rough/metal on top and reducing its opacity shows more and more of the base white or grey layer.

2

So you want: value = 1 - value. There is subtraction or oneMinus node for that.

3

i tried the subtract in a couple combinations and that ended up strange.
if part of the metal texture mask is white and its strength is lessened, i want that area to stay white (if the metallic value is set to 1) and the black parts to fade to white. (it should all fade to black if the metallic value was set to 0) does that make sense? i want to be able to fade a texture into whatever solid value is defined elsewhere, but not have that solid value mess with the texture while its strength is at/near 1