I’ve got a couple of textures-sets that have maps for diffuse, normal and specular, but not for roughness. I’d like to use “Texture Compositing” to use the normal map’s own alpha channel with the “Add normal roughness to alpha” option. So then I would have RGB for normals and A for roughness in the same texture. The problem is: the alpha channel is already full white and I can’t add to it
So, I need a black/zeroed alpha channel. There doesn’t seem to be a way to achieve this in UE4. I’m not much of an artist and the only picture editing programs I have installed are windows paint, which seems to completely ignore the existence of alpha channels, and GIMP. I tried making the texture all transparent, but this affects the color channels as well, making them useless.
How can I solve this?..