Table of Contents

The Reflection tab is part of the V-Ray Mtl parameters.


Input Sockets

You can access these sockets, when you roll out the Reflection tab of the node. This section describes the input sockets of the node. They can be used to attach external nodes to determine these values.


Reflection Color – Allows a color node to determine the reflection color and intensity. The intensity is derived from the Value property of the color.

Reflection Glossiness – Allows a float node to determine the reflection's glossiness.

GGX Tail Falloff – Allows a float node to determine the GGX Tail Falloff.

Fresnel IOR – Allows a float node to determine the Fresnel IOR.

Metalness – Allows a float node to determine the metalness of the material.

Anisotropy(-1..1) – Allows a float node to determine the Anisotropy value. The float needs to output values between -1 and 1.

Anisotropy Rotation – Allows a float node to determine the Anisotropy Rotation.

Anisotropy Uvwgen – Allows a Mapping node to be connected to edit the placement of the reflections.

Thickness Blend – Allows a float node to determine the Thickness Blend.

Thin Film IOR – Allows a float node to determine the Thin Film IOR value.


Properties

BRDF Type - Determines the type of BRDF (the shape of the highlight). See the BRDF example. When the Mode is set to OpenPBR, this parameter is disabled.

Phong - Phong highlight/reflections
Blinn - Blinn highlight/reflections
Ward - Ward highlight/reflections 
GGX - GGX Microfacet highlight/reflections


GGX is the most modern and flexible BRDF (Bidirectional reflectance distribution function) type and is able to better represent a broad range of materials thanks to its ability to control the shape of the specular lobe.

There currently isn't any particular performance difference between models, and there is little reason to choose any of the other types. 

Historically, the Phong, Blinn, Ward, and GGX are successive reflectance models developed over the years in computer graphics where each model aimed to improve on the limitations of the previous ones. For example, the specular highlights with the Phong model have a very narrow and bright center with no falloff, but it doesn't work well with anisotropic reflections. The Blinn model has broader highlight center with a tight falloff. The Ward model has an even broader center and falloff. The GGX model has a bright center and an even longer falloff (at default settings). In the past, each model's characteristics resembled a certain type of material more closely; for example, Phong could be used for plastics, Ward for cloth and metals, and Blinn for other common surfaces. However with the introduction of the GGX model, all of these surfaces can be approximated well, thus reducing the need for using the other models. 

It should be noted that no principled model is able to represent all possible materials entirely accurately, and where those models fail - for example, when the material isn’t viewed frontally - only approaches such as that of VRscans are able to capture the correct material representation.


Reflection Color - The reflection color. Note that the reflection color dims the diffuse surface color. A node can also be used to control this property. See the Reflection Color example.

Glossiness - Controls the sharpness of reflections. A value of 1.0 means perfect mirror-like reflection; lower values produce blurry or glossy reflections. A node can also be used to control this property. See the Reflection Glossiness example. When the Use Roughness option in the Reflection tab is enabled, this parameter works as Roughness and controls the roughness amount (a value of 1 produces blurry reflections). When the Mode is set to OpenPBR, this property is renamed to Rougness. It's values create the opposite effect.

GGX Tail Falloff – Controls the transition from highlighted areas to non-highlighted areas when the BRDF Type is set to GGX. When the Mode is set to OpenPBR, this parameter is disabled.

Metalness – Controls the reflection model of the material from dielectric (metalness 0.0) to metallic (metalness 1.0). Note that intermediate values between 0.0 and 1.0 do not correspond to any physical material. This parameter can be used with PBR setups coming from other applications. The reflection color should typically be set to white for real-world metals. A node can also be used to control this property.

Use Roughness – This option controls how Glossiness is interpreted. When Use Roughness is selected, the Glossiness inverse value is used. For example, if Glossiness is set to 1.0 and Use Roughness is selected, this results in diffuse shading. Conversely, if Glossiness is set to 0.0 and Use Roughness is selected, this results in sharp reflection highlights. When the Mode is set to OpenPBR, this parameter is disabled.




Example: BRDF Type

Microfacet GTR (GGX)

Modern, versatile BRDF type; suitable for all kinds of materials.

Phong

Best used for plastic surfaces.


Ward

Useful for cloth materials and chalk-like surfaces.


Click on the images to view them in full size


Blinn

Multi-purpose BRDF; suitable for many common materials.


Example: Reflection Color


This example demonstrates how the Reflection Color parameter controls the reflectivity of the material. Note that this Color also acts as a filter for the Diffuse Color (e.g., stronger reflections dim the diffuse component).


Reflection Color = 0.0, 0.0, 0.0

Reflection Color = 0.6, 0.6, 0.6

Reflection Color = 1.0, 1.0, 1.0


 

Example: Reflection Glossiness

 

This example demonstrates how the Glossiness parameter controls the highlights and reflection blurriness of the material. For this example, we have used the HSV color range, but the same results can be achieved with these values and the RGB color range. Fresnel IOR = 3.5.


Glossiness = 0.0

Glossiness = 0.5

Glossiness = 1.0


Fresnel


Fresnel Reflections – Enabling this option makes the reflection strength dependent on the viewing angle of the surface. Some materials in nature (glass etc) reflect light in this manner. Note that the Fresnel effect depends on the index of refraction as well. See the Fresnel example.

Lock Fresnel IOR – Allows you to unlock the Fresnel IOR parameter for finer control over the reflections.

Fresnel IOR –  The Index of reflection to use when calculating Fresnel reflections. Normally, this is locked to the Refraction IOR parameter, but you can unlock it for finer control. A node can also be used to control this property.





Example: Fresnel


This example demonstrates the effect of the Fresnel Reflections option. Note how the strength of the reflection varies with the Fresnel IOR of the material. For this example, the Reflection Color is pure white (1.0, 1.0, 1.0).



Fresnel IOR = 1.6


Fresnel IOR = 4.0


Fresnel IOR = 7.6


Anisotropy


Anisotropy(-1...1) – Determines the shape of the highlight. A value of 0.0 means isotropic highlights. Negative and positive values simulate 'brushed' surfaces. The accepted values are in the range from 0.99 to -0.99. See the example.

Anisotropy Rotation – Determines the orientation of the anisotropic effect in a float value between 0.0 and 1.0 (where 0.0 is 0 degrees and 1.0 is 360 degrees). See the example.

UV Vectors Derivation – Specifies the method for deriving anisotropy axes:

Local object axis – Uses a local axis for the anisotropy effect. 
Specified uvw generator – Allows the user to connect a Mapping node for the anisotropy effect.

Anisotropy Axis – Specifies a local object axis for the anisotropy effect when UV Vectors Derivation is set to Local object axis.




Example: Anisotropy(-1...1) and Anisotropy Rotation

This example demonstrates the effect of the Anisotropy(-1...1) and Anisotropy Rotation parameters, which determine the shape of the highlight. The BRDF Type is set to Microfacet GTR (GGX).


Anisotropy(-1...1) = -0.8

Anisotropy(-1...1) = 0.0

Anisotropy(-1...1) = 0.8



Anisotropy Rotation = 0

Anisotropy Rotation = 0.5

Anisotropy Rotation = 1


Thin Film


Enable Thin Film – Toggles the thin film effect on and off. When disabled, all other parameters in this rollout are inactive.

Thickness Min (nm) – Determines the minimum thickness of the thin film in nanometers. See the example.

Thickness Max (nm) – Determines the maximum thickness of the thin film in nanometers when a texture is assigned to the Thickness Blend slot. If there is no texture map, only the Min thickness value is used.

Thickness Blend – A map used to blend between the Min and Max Thickness parameters. It is expected to be in the range of 0-1. A node can also be used to control this property.

Thin Film IOR – Specifies the reflective index of the thin film. A map can be attached to this slot. A node can also be used to control this property.





Example: Thickness Min (nm)

This example shows how the Thickness Min (nm) parameter affects the V-Ray Material when no Thickness Blend is applied. The Thin Film IOR is set to 1.4.

  



Thickness Min (nm) = 0

 
Thickness Min (nm) = 300


Click on the images to view them in full size



Thickness Min (nm) = 600

Reflection Advanced

Trace Reflections – When disabled, reflections are not traced even if the reflection color is greater than black. This can be disabled to produce only highlights. Note that when disabling this parameter, the diffuse color is not dimmed by the reflection color, as would happen normally.

Max Depth – The number of times a ray can be reflected. Scenes with lots of reflective and refractive surfaces may require higher values to look correct.

Enable Dim Distance – Enables the Dim Distance parameter, which allows you to stop tracing reflection rays after a certain distance.

Dim Distance – Specifies a distance after which the reflection rays are not traced, when Enable Dim Distance is active.

Dim Fall-off – A fall-off radius for the dim distance, when Enable Dim Distance is active.

Reflect On Back Side – When enabled, reflections are computed for back-facing surfaces, too. Note that this affects total internal reflections, too (when refractions are computed).

Soften – Softens the edge of the BRDF at light/shadow transitions.

Affect Channels – Allows you to specify which channels are going to be affected by the reflectivity of the material.

Color only – The reflectivity affects only the RGB channel of the final render.
Color+alpha – Causes the material to transmit the alpha of the reflected objects instead of displaying an opaque alpha.
All channels – All channels and render elements are affected by the reflectivity of the material.





See Previous:

V-Ray Mtl Diffuse

See Next:

V-Ray Mtl Coat


Was this helpful?