In the diagram below, do the pointers of micro and macro signify that a micro surface is usually when the material is concave down relative to the air and macro concave up? How does this correlate to flat & rough vs. bumpy & specular.
Microsurface refers to to the actual microfacet surfaces, the ones that are above the side of the air while macrosurface refers to the smooth surface with is the actual line itself. I assume flat and rough would be mean the dotted line and how light reflects normal to it and bumpy and specular means that light is reflected based on the structure above the line.
I think if you keep zooming in on the microsurface you can keep getting smaller microsurfaces for a while (e.g. the parts that look flat on the microsurface in the diagram actually have small bumps and irregularities themselves), in a coastline paradox sort of way.