From Physics to shader
Physical materials can do three things
Reflectionirregularities create a blur reflection – microfacet distributiona shader asumes there are small irregularities to create the overall surface look.
Cg material components the ingredients used to recreate real world behaviour
- Reflection – equation for the part go the rays that are less than 100% brought. normally you can choose from different distribution models. (Blinn,phong, ggx…)
- Diffuse this is an approximation of an 100% bought reflection or a surface where the SSS is smaller in size than a pixel screen space
- Transmission / refraction equation for the part of the light that enters the materials paired with absorption and scattering it can create a sub surface scattering component of the material.
Dielectric – can reflect transmit and absorb
Conductors – can only reflect and absoprtion.