Diffuse – The diffuse color of the material. Note that the actual diffuse color of the surface also depends on the reflection and refraction colors.

Roughness – Used to simulate rough surfaces or surfaces covered with dust (for example, skin, or the surface of the Moon). For more information, please see the Roughness Parameter example below.

Some options are available only in Advanced mode.

Reflection – Enables reflection of the material.

Reflection Color – Specifies the reflection color. For more information, please see the Reflection Color Parameter example below.

Highlight Glossiness – Enables a separate glossiness control for the specular highlights of the material. Enabling this option and setting the value to 1.0 disables the specular highlights. 

Reflection Glossiness – Specifies the sharpness of reflections. A value of 1.0 means perfect mirror-like reflection; lower values produce blurry or glossy reflections. For more information, please see the Reflection Glossiness Parameter example below.

Fresnel – When enabled, the reflection strength depends on the viewing angle of the surface. Some materials in nature (e.g. glass, etc.) reflect light in this manner. Note that the Fresnel effect depends on the index of refraction as well. For more information, please see the Fresnel Option example below.

Reflection IOR  – When disabled, the Refraction IOR is used as Reflection IOR. Enable for finer control over the Reflection IOR. 

BRDF – Determines the type of BRDF (the shape of the highlight). There are 4 types available - Phong, Blinn, Ward, Microfacet GTR (GGX). For more information, please see the BRDF Type example below.

Back Side Reflect – When disabled, reflections are calculated for the front side of the objects only. When enabled back-side reflections are also calculated. 

Glossy Fresnel – When enabled, it uses glossy reflections and refractions. It takes the Fresnel equation into account for each microfacet of the glossy reflections, rather than just the angle between the viewing ray and the surface normal. The most apparent effect is less brightening of the grazing edges as the glossiness is decreased. With the regular Fresnel, objects that are less glossy may appear to be unnaturally bright and glowing at the edges. The Glossy Fresnel calculations make this effect more natural.

Max depth – Specifies the number of times a ray can be reflected. Scenes with lots of reflective and refractive surfaces may require higher values to look right.

 GTR Tail Falloff – Active only when the BRDF is set to GGX. It allows fine tuning of the specular reflections by controlling the rate at which the sharp specular highlight fades out. Higher values create a value spread out the fade out of the highlight. This parameter does not affect the size of the actual highlight - this is controlled by the Reflect glossiness paramater. For more information, please see the GTR tail falloff example below.

Affect Channels – Specify which channels are affected by the reflectivity of the material.

Color Only – The reflectivity of the material 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 – The reflectivity of the material affects all channels and render elements.

Example: BRDF Type

This example demonstrates the differences between the BRDFs available in V-Ray.

Example: GTR Tail Falloff

This example demonstrates the effect of the GTR tail falloff parameter. 

Anisotropy (-1 to 1) – Determines the shape of the highlight. A value of 0.0 means isotropic highlights. Negative and positive values simulate brushed surfaces. For more information, please see the Anisotropy example below.

Rotation – Determines the orientations of the anisotropic effect in a float value between 0 and 1 (where 0 is 0 degrees and 1 is 360 degrees). For more information, see the Rotation example below.

Derivation – Determines the anisotropy orientation method. 

Local Axis – The orientation of the anisotropic reflection/highlight is based on the object's local X, Y or Z axis. 
UVW – When enabled, the orientation of the anisotropic reflection/highlight is based on the specified map channel/set. 

Local Axis – Specifies a local axis used for Anisotropy orientation. (X, Y, Z)

Map Channel/Set – Specifies a map channel that is used for the anisotropic reflections/highlights orientation. 

Dim Distance – Enables Dim Distance. 

Distance – Specifies a distance after which the reflection rays are not traced. 

Dim Falloff –  Sets a fall off radius for the dim distance. 

 Example: The Reflection Color Parameter

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.

 Example: The Reflection Glossiness Parameter

This example demonstrates how the Reflection glossiness parameter controls the highlights and reflection blurriness of the material.

Some options are available only in Advanced mode.

Refraction – Enables Refraction of the material.

Refraction Color – Specifies the refraction color. Note that the actual refraction color depends on the reflection color as well. For more information about refraction color, please see the Refraction Color Parameter example below.

Fog color – Specifies the attenuation of light as it passes through the material. This option allows to simulate the fact that thick objects look less transparent than thin objects. Note that the effect of the fog color depends on the absolute size of the objects and is therefore scene-dependent unless the Fog Units Scaling is enabled. The fog color also determines the look of the object when using fog scattering. For more information, please see the Fog Color Parameter and Fog Multiplier Parameter examples below.

Fog Multiplier – Smaller values reduce the effect of the fog, making the material more transparent. Larger values increase the fog effect, making the material more opaque.

Fog Bias  – Changes the way the fog color is applied. Negative values make the thin parts of the objects more transparent and the thicker parts more opaque and vice-versa (positive numbers make thinner parts more opaque and thicker parts more transparent).

IOR – Specifies the index of refraction for the material, which describes the way light bends when crossing the material surface. A value of 1.0 means the light does not change direction. For more information, please see the Refraction IOR Parameter example below.

Refraction Glossiness – Specifies the sharpness of refractions. A value of 1.0 produces perfect glass-like refraction; lower values produce blurry or glossy refractions. For more information, please see the Refraction Glossiness Parameter example below.

Affect shadows – When enabled, the material casts transparent shadows, depending on the refraction color and the fog color. This only works with V-Ray shadows and lights.

Fog Units Scaling – When enabled, the fog color attenuation becomes dependent on the current system unit.

Max depth – Specifies the number of times a ray can be refracted. Scenes with lots of refractive and reflective surfaces may require higher values to look right.

Affect channels – Specifies which channels are affected by the transparency of the material.

Color Only – The transparency of the material affects only the RGB channel of the final render.
Color+Alpha – Causes the material to transmit the alpha of the refracted objects instead of displaying an opaque alpha. Note that currently this works only with clear (non-glossy) refractions. 
All Channels – The transparency of the material affects all channels and render elements.

Dispersion – When enabled, true light wavelength dispersion is calculated. For more information, please see the Dispersion example below.

Abbe – Increases or decreases the dispersion effect. Lowering it widens the dispersion and vice versa.

Fog Scattering – Enables Refraction translucency.

Type – Selects the algorithm for calculating Fog Scattering (also called sub-surface scattering). Note that Refraction must be enabled and a Refraction Fog should be different from white for this effect to be visible. 

Hard (wax) model  – This model is specifically suitable for hard materials like marble. 
Hybrid – This is the most realistic SSS model and is suitable for simulating skin, milk, fruit, juice, etc. 

Back-side Color – Normally the color of the subsurface scattering effect depends on the Fog color. This parameter allows you to additionally tint the SSS effect. 

Scatter Coeff – The amount of scattering inside the object. 0.0 means rays are scattered in all directions; 1.0 means a ray cannot change its direction inside the sub-surface volume.

Fwd/back Coeff – Controls the direction of scattering for a ray. 0.0 means a ray can only go forward (away from the surface, inside the object); 0.5 means that a ray has an equal chance of going forward or backward; 1.0 means a ray are scattered backward (towards the surface, to the outside of the object).

Thickness ² – Limits the rays that are traced below the surface. This is useful if you do not want or don't need to trace the whole sub-surface volume.

Light Multiplier – Multiplies the translucent effect. 

Example: The Refraction Color Parameter

This example demonstrates the effect of the Refraction color parameter to produce glass materials. The material has a gray Diffuse color, white Reflection color, and the Fresnel option is turned on.

Example: The Fog Color Parameter

This example demonstrates the effect of the Fog color parameter. Notice how the thick areas of the object are darker in the two images on the right because of the light absorption of the fog.

Example: The Fog Multiplier Parameter

This example demonstrates the effect of the Fog multiplier parameter. Smaller values cause less light absorption because of the fog; while higher values increase the absorption effect.

Example: The Refraction IOR Parameter

This example demonstrates the effect of the Refraction IOR parameter. Note how light bends more as the IOR deviates from 1.0. When the index of refraction (IOR) is 1.0, the render produces a transparent object. Note however, that in the case of transparent objects, it might be better to assign an opacity map to the material, rather than use refraction.

Example: The Refraction Glossiness Parameter

This example demonstrates the effect of the Refraction glossiness parameter. Note how lower Refraction glossiness values blur the refractions and cause the material to appear as frosted glass.

Example: The Refraction Depth Parameter

This example shows the effect of the Refraction depth parameter. Note how too low of a refraction depth produces incorrect results and areas with total internal reflection are also affected by the Reflection depth.

Some options are available only in Advanced mode.

Opacity – Specifies how opaque or transparent the material is. A texture map can be assigned to this channel. 

Custom Source – When enabled, V-Ray uses an alpha channel to control the material opacity. 

Diffuse Texture Alpha – The diffuse texture alpha channel controls the opacity. Diffuse Texture Alpha source works the same way as Diffuse Map Alpha as Transparency legacy option from the V-Ray versions before 3.60. 
Opacity Texture Alpha – The opacity texture alpha channel controls the opacity, instead of the default texture intensity. If there is no texture in the source slot, the option is ignored. 

Mode – Controls how opacity is sampled.

Normal – (Legacy) The opacity map is evaluated as normal: the surface lighting is computed and the ray is continued for the transparent effect. The opacity texture is filtered as normal.
Clip – (Very fast) The opacity texture is not filtered and it is clipped to either fully opaque or fully transparent based on the mid-point value. Useful when there are many transparent surfaces one behind the other like leaves.
Stochastic – (Optimal) The opacity texture is filtered and the surface is randomly shaded as either fully opaque or fully transparent for a correct average appearance.

Mode – Specifies if Multiplier or Blend Amount parameters are used to control the intensity of other parameters.

Multiplier – For applicable parameters, intensity is controlled through a Multiplier parameter.
Blend Amount – For applicable parameters, intensity is controlled through a Blend Amount parameter.

Diffuse – Controls the intensity of the Diffuse color.

Reflection Color – Controls the intensity of the reflection color.

Reflection Glossiness – Controls the intensity of the reflection sharpness.

Refraction Color – Controls the intensity of the refraction color.

IOR – Controls the intensity of the Index of Refraction value when calculating refraction.

Refraction Glossiness – Controls the intensity of the refraction sharpness.

Opacity – Controls the intensity of the overall material Opacity.