metallicRoughnessTexture

The metallic-roughness texture. The metalness values are sampled from the B channel. The roughness values are sampled from the G channel. These values MUST be encoded with a linear transfer function. If other channels are present (R or A), they MUST be ignored for metallic-roughness calculations. When undefined, the texture MUST be sampled as having 1.0 in G and B components.