"Reflection from surfaces can be split into four broad categories: diffuse, glossy specular, perfect specular and retro-reflective. Diffuse surfaces scatter light equally in all directions. Most real surfaces exhibit reflection that is a mixture of these four types. Although a perfectly diffuse surface isn't physically realizable, examples of near-diffuse surfaces include dull chalkboards and matte paint. Glossy specular surfaces such as plastic or high-gloss paint scatter light preferentially in a set of reflected directions - they show blurry reflections of other objects. Perfect specular surfaces scatter incident light in a single outgoing direction. Mirrors and glass are examples of perfect specular surfaces. Finally, Retro-Reflective surfaces like velvet or the Earth's moon scatter light primarily back along the incident direction."
- Physically Based Rendering 2nd Edition, Matt Pharr, Wenzel Jakob and Greg Humphreys
The two types of component here are used for reflection and transparency and are fully named:
- Bidirectional Reflection Distribution Function
- Bidirectional Transmittance Distribution Function
Each has further options that are revealed by double-clicking on the nodes.
Good for metals or glass, hard glossy specular surfaces that have very short tails for specular highlights.
One of the oldest material components for glossy specular reflectance, this along with Lambert was the basis for LightWave surfacing in LightWave 2015 and before.
GGX is Walter, Marschner, Li and Torrance's expansion on the Generalized Trowbridge-Reitz model for shading of metallic surfaces. This is currently the cutting edge for glossy specular reflection, with a longer tail for specular reflections.
The simplest form of diffuse reflection, also a staple for LightWave up to 2015.
A shader updated from Lambert that deals with matte surfaces in a far more realistic manner.
A simple subsurface scattering shader. It has no forward/back scattering switch, but will be faster than using the SSS from a more complex shader like PBSDF.
A simple specular shader with no reaction to lights, etc. It uses one sample. Extremely fast if you just want glass or liquid that doesn't react to scene lights.