Specular materials (metals and dieletrics)
Conductors (metals) and dielectrics (glasses, liquids, ...) are materials that both reflect and transmit light. They are defined by their index of refraction (how the light is deflected or reflected when entering the material) and their index of extinction (how much of the light is absorbed by the material). Both indexes can be measured and they can be simulated in Predictive Engine.
Conductors and dielectrics are both designed with an index of refraction and an index of extinction/absorption. The choice of the type (Dielectric or Conductor) is an optimization setting for Predictive Matter :
if a material is dielectric, the light can be transmitted inside the material : the path tracer will try and find a path through the material,
if a material is conductor, the light cannot be transmitted inside the material : the path tracer will only compute paths reflected by the material.
Examples of measured conductors
Examples of non-absorbing dielectrics
Specular materials can also be modelled as :
Perfect mirrors : conductors that are defined by their reflectivity only, they reflect 100% of the light they receive. Be aware that this is a model and cannot exist in real life,
Colored glasses : dielectrics that are defined by their index of refraction and their color.
See the Spectrums section for more details on spectrums.
Examples of perfect mirrors
Examples of colored glasses
The normals of the geometry are very important for "Specular" and "Interface" materials : see the Geometry section for more details on the normals.
You can define more complex specular materials using the "Interface" shader. This shader enabled you to add coatings on the material, define "Thin" materials with a given thickness, or define an external material if the internal material is not in contact with air (water in a glass for instance).