A roughness map varies microsurface roughness across a material; low values produce sharper reflections and high values spread them more broadly.
- Low value
- Sharper reflection
- High value
- Broader reflection
- Data type
- Non-color / linear
- glTF packing
- Green channel
Read response, not just grayscale
The same gray value can feel different depending on normal detail, metallic state, light size, and environment contrast. Rotate the lighting when evaluating it.
Packed textures need correct channels
glTF commonly packs roughness into the green channel of a metallic-roughness texture. Importers must preserve the channel assignment and treat it as linear data.