When exporting from Rhino to OBJ, meshes seem to always be merged by material, regardless of layers, groups, objects, etc. You can test by importing the OBJ back into Rhino.
This is troublesome when I need to work with the meshes individually in other software but keep the same material.
Other formats like Collada preserve the meshes, but I prefer to work with OBJ/MTL. Is there some setting or export option that I’m missing?