VRayMtl

The VRayMtl is a versatile material that allows for better physically correct illumination (energy distribution) in the scene. This material can be easily set up to simulate a variety of surfaces from plastics, metals, and glass. Furthermore, you can define the BRDF to decide how you want light to interact with the surface material.

This page is based on the VRayMtl shader documentation, for more information see docs.chaosgroup.com/display/VRAY4MODO/V-Ray+Material.

Inputs

Control

Type

What it does

Notes
toggle Toggles the influence of channels connected to the shader without disconnecting them from the shader input. Displacement is toggled off by default.
button Creates a new Channel.  

Inputs | Diffuse Color

dropdown

 The channel controlling the diffuse color of the material. The actual diffuse color of the surface might also be affected by the reflection and refraction colors.
Inputs | Diffuse Amount dropdown The channel controlling the diffuse amount of the material.  
Inputs | Opacity Map dropdown The channel containing the opacity map (to determine which parts of the material are opaque or translucent) for the material.  

Inputs | Roughness Amount

dropdown

The channel specifying the roughness amount on the surface.

  

Inputs | Self-Illumination

dropdown

The channel specifying the areas on the material that are self-illuminated.

  
Inputs | Reflection Color dropdown The channel controlling the color on the areas of the material where light is reflected.  
Inputs | Reflection Amount dropdown The channel controlling the reflection amount on the material.  
Inputs | Reflection Glossiness dropdown The channel specifying the areas on the material where there is glossiness on a highlight.  
Inputs | Fresnel IOR dropdown The channel controlling the Fresnel IOR of the material.  

Inputs | GGX Tail Falloff

dropdown

The channel controlling the GGX Tail Falloff of the material.

  

Inputs | Metalness

dropdown

 The channel controlling the Metalness of the material.  
Inputs | Anisotropy dropdown The channel specifying the direction of the anisotropic rotation.  
Inputs | Anisotropy Rotation dropdown The channel controlling the color of the areas on the material where light is refracted.  
Inputs | Refraction Color dropdown The channel specifying the areas on the material where there is glossiness on a refractive surface.  
Inputs | Refraction Amount dropdown The channel controlling the color of the areas on the material where fog (the attenuation of light as it passes through a material) appears, so that thick objects look less transparent than thinner objects.  
Inputs | Refraction Glossiness dropdown

The channel controlling the color of the areas of translucency (or sub-surface scattering) in a material.

  
Inputs |
Refraction IOR		 dropdown The channel containing the bump map.  
Inputs |
Fog Color		 dropdown The channel controlling the fog color of the material.  
Inputs |

Translucency Color		 dropdown The channel controlling the translucency color of the material.  
Inputs |

Normal		 dropdown The channel controlling the normal map of the material.  
Inputs |
Bump		 dropdown The channel controlling the bump map of the material.  
button Inverts the channel values of the selected Bump channel.  
Inputs |

Vector		 dropdown The channel controlling the vector map of the material.  
Inputs |
Displacement		 dropdown The channel controlling the displacement map of the material.  

Shader

Control Type What it does Notes
Basic Properties | Diffuse Color swatch The base diffuse color on the object for the Diffuse Color channel.  
Basic Properties | Diffuse Amount text field, slider The base diffuse color amount on the object for the Diffuse Amount channel.  
Basic Properties | Opacity Map swatch Sets the color for the Opacity Map channel.  
Basic Properties | Roughness Amount text field, slider The level of roughness of the diffuse component in the Diffuse Roughness channel. Higher values result in a rougher surface.  
Basic Properties | Self-Illumination swatch The self illumination color of the material.  
Reflection | Reflection Color swatch The reflection color. The reflection color dims the diffuse surface color.
Reflection | Reflection Amount text field, slider Controls the objects overall reflectivity. The more reflective the material becomes, the less diffuse color it emits.
Reflection | Reflection Glossiness text field, slider Controls the sharpness of reflections. A value of 1.0 means mirror-like reflection, and lower values produce blurry or glossy reflections.  
Reflection | Metalness text field, slider Controls the metalness of the material. A value of 0 means the shader doesn't look metallic at all, a value of 1 means the material takes on a metal appearance.  
Reflection | GGX Tail Falloff text field, slider Defines the transition from highlighted areas to non-highlighted areas when BRDF Type is set to GGX.  
Reflection | Use Fresnel toggle When toggled on, makes the reflection strength dependent on the viewing angle of the surface. Fresnel also depends on the Fresnel IOR value.
Reflection | Glossy Fresnel toggle When toggled on, uses glossy Fresnel to interpolate glossy reflections and refractions. This control is permanently locked, since the calculations involved result in a more realistic appearance for edges with lower glossiness.
Reflection | Lock Fresnel IOR to Refract... toggle Locks the Fresnel effect to the Refraction IOR value. Unlock this for finer control when needed.
Reflection | Fresnel IOR text field, slider The Index of Refraction used when calculating Fresnel reflections. Normally this is locked to Refraction IOR parameter, but when unlocked provides you with finer control.
Reflection | Use Roughness toggle Determines whether Roughness Amount is used in the reflection of the material.  
Reflection | BRDF Type dropdown

BRDF is an equation that defines how light is reflected off a surface. The BRDF Type determines the highlight's general shape:

• Phong - Phong highlights/reflections.

• Blinn - Blinn highlights/reflections.

• Ward - Ward highlights/reflections.

• GGX - GGX highlights/reflections.

 GGX is the most modern and flexible BRDF type, and is able to represent a broader range of materials due to its ability to control the shape of the specular lobe.
Reflection | Trace Reflections toggle When disabled, reflections are not traced even if Reflection Color is other than black. You can disable this option to produce only highlights. When this option is disabled, the Diffuse Color is not dimmed by the Reflection Color, as would normally happen.
Anisotropy | Anisotropy text field, slider Determines the roundness of the highlights. A value of 0.0 means isotropic (round) highlights, while other values elongate the highlight. Negative and positive values simulate brushed metal surfaces.
Anisotropy | Anisotropy Rotation text field, slider Determines the orientation of the anisotropic effect. A value of 0 is 0 degrees, and a value of 1.000 is 360 degrees.  
Anisotropy | Local Object Axis dropdown

Determines the direction in the local object axis of the anisotropic effect.

 
Refraction | Refraction Color swatch Determines the refraction color. Refraction color depends on the Reflection Color as well.
Refraction | Refraction Amount text field, slider The amount of refraction in the material.  
Refraction | Refraction Glossiness text field, slider Controls the sharpness of the refractions. A value of 1.0 means glass-like refraction, and lower values produce blurry or glossy refractions.  
Refraction | Refraction IOR text field, slider 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 will not change direction.  
Refraction | Trace Refractions toggle Enables refractions for the material.  
Refraction | Fog Color swatch The attenuation of light as it passes through the material. It simulates the fact that thick objects look less transparent than thin objects. The effect of the fog color depends on the absolute size of the objects and is therefore scene-dependent.
Refraction | Fog Multiplier text field, slider The strength of the fog effect. Smaller values make the material appear more transparent, larger values make the material appear more opaque.  
Refraction | Fog Bias text field, slider Changes the way the Fog Color is applied. Negative values make the thin parts of the object more transparent, and thicker parts more opaque. Positive values make the thin parts more opaque, and the thicker parts more transparent.  
Subsurface Scattering | SSS On toggle Turns subsurface scattering on or off. Has no perceivable effect in the Mari viewport.
Subsurface Scattering | Translucency Color swatch Normally the color of the sub-surface scattering effect depends on the Fog Color. The Translucency Color adds tint to the SSS effect. Has no perceivable effect in the Mari viewport.
Subsurface Scattering | Fwd/back Coefficient text field, slider Controls the scatter direction of a ray. A value of 0.0 means a ray moves away from the surface. A value of 1.0 means a ray will move towards the surface. Has no perceivable effect in the Mari viewport.
Subsurface Scattering | Scatter Coefficient text field, slider Defines the amount of scattering inside the object. A value of 0.0 means rays are scattered in all directions. A value of 1.0 means a ray cannot change its direction inside the sub-surface volume. Has no perceivable effect in the Mari viewport.
Subsurface Scattering | Thickness text field, slider Limits the rays that are traced below the surface.

This option is useful if you don't need to trace the whole sub-surface volume.

Has no perceivable effect in the Mari viewport.
Misc | Double Sided toggle When enabled, VRay flips the normals for back-facing surfaces with this material applied.  
Misc | Approximate Environment toggle    
Misc | Environment Samples text field, slider    
Displacement | Displacement Bias text field, slider How much the white or black values are pushed or pulled from the surface.  
Displacement | Displacement Scale text field, slider How much displacement is applied to the shader. Lower values equal smaller displacement; higher values equal larger and more obvious displacement.  
Displacement | Displacement Range text field, slider What the range of displacement is. This setting is multiplied by the Displacement Scale to give the displacement.  
Displacement | Max Tessellation text field, slider The maximum amount of texels the surface is tessellated to.  
Displacement | Perturb Normals dropdown Selecting Yes changes the displacement so that it moves the surface but leaves the surface normals as they are.  
Bump | Bump Weight text field, slider How much weight the bump map has. Lower values are smaller bumps, higher values are larger and more obvious displacements.  
Bump | Bump Mode dropdown Displays bump quickly (Fast), accurately (Accurate), or less accurately (Fastest).  
Bump | Bump Space dropdown

• UV - Normals are calculated relative to the UV coordinates space.
The UV Bump Space mode is the more traditional approach but can lead to noticeable seams and color variations.

• World - Normals are calculated relative to the World coordinates space.
Using the World Bump Space mode gives a more seamless result.