The metallic property defines whether the surface is a metallic (conductor)
or a non-metallic (dielectric) surface. This property should be used as a
binary value, set to either 0 or 1. Intermediate values are only truly useful
to create transitions between different types of surfaces when using textures.
The default value is 0.
The reflectance property only affects non-metallic surfaces.
This property can be used to control the specular intensity. This value
is defined between 0 and 1 and represents a remapping of a percentage of
reflectance. The default value is 0.5.
The roughness property controls the perceived smoothness of the surface.
When roughness is set to 0, the surface is perfectly smooth and highly glossy.
The rougher a surface is, the âblurrierâ the reflections are.
The default value is 0.4.