The Metallic layer is used for highly reflective materials that have colored reflections. 


Metallic Layer

Figure 1: Metallic layer parameters


Metallic Layer Parameters

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

Specular - The specular reflection channel, which determines the metallic color when the Metallic Reflection Mode is set to Artistic.

Edge Tint - The color of the edges of the metal material, only used with Artistic and IOR+Color modes.

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 - The Metallic layer's roughness.

Anisotropy - Controls the material's reflectance uniformity. If the reflectance changes based on the orientation or the surface rotation, it is Anisotropic. If the reflectance is uniform in all directions and does not change based on the orientation or surface rotation, it is Isotropic. By default, this attribute is 0 and it sets the Metallic material as Isotropic. Non-zero values mean the material exhibits Anisotropic reflectance, where -1 is horizontal and 1 is vertical.

Rotation - The Metallic Anisotropic reflection's rotation.

Spread - Determines the tail spread of the specular BSDF.

IOR

Metallic Reflection Mode - This changes how OctaneRender® calculates reflectivity.

  • Artistic - Uses the Specular color. The values entered into the IOR have no impact. It is simple and ideal for non-realistic results.
  • IOR + Color - Uses n and k IOR values as Index of Refraction along with the Specular Color. 
  • RGB IOR - The most accurate IOR mode. Uses the three IOR values; red (650nm), green (550nm), and blue (450 nm) and ignores the Specular color. Standard IOR (n)  and Extintion Coefficient (k) are actual index values. For these values go to refractiveindex and enter real IOR values according to material types you selected. Use the numeric field for n on the left and k on the right for each of the IOR, IOR (Green), and IOR (Blue) parameters listed below.

Index Of Refraction - Complex-valued IOR (n-k*i) controlling the specular reflection's Fresnel effect, where n = the refractive index and k = the attenuation or extinction coefficient. For RGB mode, the IOR for red light (650nm).

Index Of Refraction (Green) - For RGB mode, the IOR for green light (550nm).

Index Of Refraction (Blue) - For RGB mode, the IOR for blue light (450nm).

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 - This sets the film coating's Index Of Refraction.

Geometry Properties

Bump - Simulates a relief 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 the layer normals using an RGB image.

Layer Properties

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.