The workflow in one line
Metallic-roughness describes a surface with a base colour plus two scalar controls - how metallic it is and how rough - and a few detail maps. It is compact, engine-friendly and physically grounded, which is why it dominates real-time PBR.
The channels
| Channel | Range | What it does |
|---|---|---|
| Base Color | sRGB colour | Albedo / diffuse colour with no lighting baked in. For metals this is the reflectance tint; for non-metals it is the diffuse colour. |
| Roughness | 0-1 (linear) | Micro-surface scatter. 0 is a perfect mirror, 1 is fully matte. Most real surfaces live in a mid band and vary across the surface. |
| Metallic | 0 or 1 | Dielectric (0) vs metal (1). Keep it near the extremes - partial values are for transitions like rust eating into bare metal, not a default. |
| Normal | tangent-space RGB | Fakes surface detail direction without geometry. The bluish map you have seen; do not treat it as a colour. |
| Height | 0-1 grayscale | Displacement / parallax detail. Often feeds the normal and can drive real displacement. |
| Ambient Occlusion | 0-1 grayscale | Baked contact shadow in crevices. Multiplied into ambient light, not direct light. |
| Emissive | colour | Self-illumination - screens, glowing runes, hot metal. Black means no emission. |
| Opacity | 0-1 | Coverage / alpha for cutouts and transparency. |
Values that read correctly
- Metallic is binary in practice. A surface is metal or it is not. Grey metallic values are the classic beginner tell.
- Roughness carries the story. Variation in roughness - polished here, worn matte there - is what sells a used surface more than base colour does.
- Base color for metals is the reflection tint, not a diffuse colour - gold, copper and brass have distinctly coloured base colours; painted or dielectric surfaces do not.
- AO belongs in ambient only. Baking hard shadows into base color double-darkens under direct light.
Metallic-roughness vs specular-glossiness
The older specular-glossiness workflow splits reflectance into a specular colour map and uses glossiness (the inverse of roughness). Metallic-roughness is leaner and less error-prone, and is the default for real-time engines. Unless a pipeline specifically requires spec-gloss, author metallic-roughness.
Set them all at once
Smart Material Studio sets sensible targets for every one of these channels per theme, shows the values in a live channel table, and lets you override roughness, metallic, normal strength and the base/emissive colours - then bakes matching base maps and writes them into the Painter script.