I am working on a project that necessitates an automated export of blender objects with materials to basically any file format that supports diffuse and roughness maps. However, some objects have topology too complex to be smart-UV unwrapped and thus cannot be texture baked on. To remedy this, I was able to use .fbx to export vertex colors. Is there a method of annotating vertices with roughness and a file format that supports it? In essence, I need to avoid the use of UV unwraps but still export roughness and diffuse data.
Once your roughness is tuned to your liking, (depending on what facilities you have to further adjust it in your destination application,) you can plug it straight into the material output, and bake its resulting Emission into a Color Attribute you've set up for the purpose:
On the left, the original texture. On the right, picked up from the baked Attribute:
If you needed to, with a Combine RGB you could arrange your shader-tree to feed 3 float/monochromatic parameters into the R,G,and B of a single Color Attribute.
The attribute's resolution will obviously depend on the density of your mesh.