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 # only 0 and 1 are physical
  metallic_map is Visuals.Textures.DefaultTexture