The Specular layer is used for shiny materials like plastics, or clear materials like glass. Refer to the Glossy, Specular, and Universal Material topics in this manual for more information.


Specular Layer

Figure 1: Specular layer parameters

 

Specular Layer Parameters

Enabled - Determines whether the material layer contributes to the overall layered material system.

Specular - The layer's coating color.

Transmission - The layer's transmission color.

BRDF Model - The BRDF (Bidirectional Reflectance Distribution Function) is a function that determines the amount of light reflected from a material when light falls on it. For Metallic materials, there are four applicable BRDF Models to choose from. Each BRDF is affected by a specific geometric property (microfacet distribution) of the surface, which describes the microscopic shape (microfacet normals) of that surface, and it serves as a function to scale the reflections' brightness in the BRDF. More details can be found in the BRDF Models topic. 

Roughness

Roughness - Controls the distribution of the reflections on the surface. Higher values will produce a rougher surface reflection.

Affect Roughness - The percentage of roughness affecting subsequent layers' roughness.

Anisotropy - The layer's anisotropy. A value of -1 is horizontal, while 1 is vertical. A value of 0 is Isotropic.

Rotation - The rotation of the specular anisotropic reflection.

Spread - Determines the tail spread of the specular BSDF.

IOR

IOR - The specular reflection's or transmission's Index Of Refraction.

Allow Caustics - If enabled, the photon tracing kernel will create caustics for light reflecting or transmitting through the object.

Thin Film Layer

Film Width - Sets the film coating's thickness.

Film IOR - Sets the film coating's Index Of Refraction.

Transmission Properties

Thin Layer - Makes the layer very thin so it reflects, or goes straight though the layer.

Geometry Properties

Bump - Simulates a relief by using a Greyscale texture interpreted as a Height map for the layer.

Bump Height - Determines the height represented by a normalized value of 1.0 in the bump texture. A vaule of 0 disables the bump map and a negative value will invert the bump map.

Normal - Distorts layer normals using an RGB image.

Layer Properties

Dispersion Coefficient - This is the B parameter of the Cauchy dispersion model. Increasing this value increases the coloration amount and dispersion in the layer’s transmission and caustics.

Dispersion Mode - Determines how the IOR and dispersion coefficients are interpreted. 

  • Abbe Number - Measures a transparent material's dispersion. A higher value indicating less dispersion and clearer color perception. 
  • Cauchy Formula - Calculates the refractive index of an optical material at any specific wavelength within the visible spectrum. 

Retro-Reflective - Activates an optical property where the surface reflects incoming light rays directly back to the original light source. Examples are street signs and safety gear. 

Layer Opacity - Controls the material layer opacity. A value of 0 will make the layer completely invisible revealing the layer below. 

Layer Weight - Defines the brightness/intensity of the layer's effect. Values less than 1 and closer to 0 make the layer appear darker and less intense, acting as an energy-scaling multiplier for the diffuse channel of the layer.