metallicroughness

Metallic-roughness is a physically based shading workflow used in real-time rendering to describe a material with three main texture inputs: albedo (base color), a metallic map, and a roughness map. It is a common approach in modern game engines and in the GLTF 2.0 asset format.

In this workflow, the metallic map is grayscale, where 0 indicates a dielectric (non-metal) and 1 a metal. The roughness map is also grayscale, with 0 meaning a smooth surface and 1 a fully rough surface. The base color encodes the diffuse color for non-metals; for metals, the base color tint influences the color of reflected light rather than a diffuse component. Lighting is computed with a microfacet reflectance model (often GGX) and Fresnel effects. Dielectrics typically have low base reflectivity (F0 around 0.04), while metals have higher reflectivity with F0 tied to their metallic base color.

The final appearance is determined per pixel by combining the material’s metalness and roughness with the lighting environment, ensuring energy conservation. This makes it possible to render a wide range of materials—from plastics and ceramics to gold and copper—using a compact set of maps.

Metallic-roughness is favored for its simplicity and efficiency in real-time rendering and is widely supported in GLTF, Unity, and Unreal Engine pipelines. Variants may pack metallic and roughness data into a single texture or supplement with additional maps such as normal or ambient occlusion for added detail.