Metalness Map
Conductor vs dielectric switch
Also known as: Metallic map
Definition
A metalness map is a grayscale texture that tells the shader which parts of a surface are metal (white, 1) and which are non-metal (black, 0). Metals and non-metals reflect light fundamentally differently in physics, so a binary mask is sufficient for almost all real materials — grey intermediate values usually indicate either dust over metal or a baking artefact.
In production
A common rule: pixels are either fully metal or fully non-metal, never in-between. Areas like rust on iron are non-metal (rust is a dielectric oxide) and should be authored as 0 in the metalness map, even though they sit on a metal object. The same logic applies to painted metal, dust, and fingerprint smudges — anything covering the base metal with a non-metallic layer resets that pixel to 0, no matter how thin the layer looks. Substance Painter's smart materials automate this by masking metalness with the same curvature and AO generators used for wear, so paint chips reveal metal (1) while intact paint stays non-metal (0). A frequent beginner error is painting metalness with a soft brush at low opacity, producing grey values around 0.3-0.6 that make the engine's shader blend between the metal and dielectric BRDF models — a physically incorrect, "washed out" reflection that no real material exhibits, since the metal/non-metal transition in nature happens at a hard boundary defined by a coating's edge, not a gradient.
