Blend modes for roughness maps?

[fattkid]

Hey folks,

I'm curious what blend modes are used when adding roughness maps to a layer stack, so I can add an additional roughness map/textures/information on top of what already exists, and have them combine together for an overall roughness affect..

For example, say I add a black and white scratches texture to be used for height and roughness - I would like to use the same scratches texture to change the roughness value of the scratches, on top of the pre existing surface roughness. I assumed linear dodge/add, but doesn't seem to work? It effects the whole mesh, not just the scratches.

So what blending modes should I be using or trying to add additional roughness information on top of or to the roughness information below it?

Thanks for any help.

[fattkid]

Anyone? Please? I'll give a dollar.

[justaviking]

You might need to share a picture or two, but I'll share a couple of thoughts....


- It sounds like your scratches have a black background instead of using a transparent background ("Alpha" layer).  True?



Interruption....  I'll be back....  sorry....
Okay, I'm back now...


I think that's why you're having problems affecting the other layers.

Maybe make a "Folder" and then you might be able to better isolate the scratches using a "Levels" node to eliminate the black.

Or...  Use your scratch image as a Stencil.  Maybe, if it's genuinely 100% black on the background.  I'm sort of guessing there.



Best thing is probably to change your black background to a transparent one.