Metallic

trait Metallic:
    .doc: """
A surface's metallic value defines whether the surface is dielectric (non-metallic, value = 0)
or not. This property can be defined for the surface as a whole or vary using a texture mapping.
Physically speaking, this property is binary and only values of 0 or 1 are physically accurate,
many engines, however, allow blending between the modes by specifying values in between.

If an metallic_map is provided, the sampled values is scaled by the constant metallic value.
Otherwise, the metallic value is used as is.
"""
    metallic is Real: 1.0
    metallic_map is Visuals.Textures.DefaultTexture

    # Propagate outer values to the physical visible light spectrum band
    visible becomes Visuals.Optics.VisibleBand with Visuals.Optics.SurfaceFeatures.Metallic:
        metallic: metallic
        metallic_map: metallic_map