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Reflection

Model – Determines the type of BRDF (the shape of the highlight and glossy reflections). This parameter has an effect only if the Reflection Color is different from black and Reflection Glossiness is different from 1.0. 

Phong – Phong highlight/reflections
Blinn – Blinn highlight/reflections
Ward – Ward highlight/reflections
MIcrofacet GTR (GGX) – GGX Microfacet highlight/reflections

GTR Tail Falloff – Controls the transition from highlighted areas to non-highlighted areas when the Model (BRDF Type Type) is set to GGX.

Color – Reflection color. Note that the reflection color dims the Diffuse Color.

Glossiness – Controls the sharpness of reflections. A value of 1of 1.0 means 0 means perfect mirror-like reflection; lower values produce blurry or glossy reflections. Use the Reflection Subdivs parameter below to control the quality of glossy reflections.

Unlock Fresnel IOR – The IOR to use when calculating Fresnel reflections. Normally this is locked to the Refraction IOR parameter, but you can unlock it for finer control.

Use Fresnel – When enabled, 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 (IOR) as well.

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Reflection

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 materials.Unlock Highlight Glossiness – When enabled, the user can enter different values for the Highlight Glossiness and Reflection Glossiness. However this will not produce physically correct results.

Glossy Fresnel – When enabled, uses glossy fresnel to interpolate 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 with low glossiness may appear to be unnaturally bright and "glowing" at the edges. The Glossy Fresnel calculations make this effect more natural.

Anisotropy

Strength – Determines the shape of the highlight. A value of 0.0 means isotropic highlights. Negative and positive values simulate "brushed" surfaces.

Rotation – Determines the orientation of the anisotropic effect in a float value between 0 and 1 (where 0 is 0 degrees and 1 is 360 degrees).

Axis – Specifies a local object axis for the anisotropy effect.

Advanced Options

Show Advanced Options – Enabling this option exposes some advanced options in this tab.

Dive to Surface Node – Press this button to dive into the Complex Material network of nodes and selects the Surface Node.

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Refraction

Color –  Refraction color. Note that the actual refraction color depends on the Reflection Color as well.

Glossiness – Controls the sharpness of refractions. A value of 1of 1.0 means 0 means perfect glass-like refraction; lower values produce blurry or glossy refractions. Use the Refraction Subdivs parameter below to control the quality of glossy refractions.

IOR – 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 does not change direction.

Absorption

Color – The attenuation of light as it passes through the material. This option helps simulate the fact that thick objects look less transparent than thin objects. Note that the effect of the absorption color depends on the absolute size of the objects and is therefore scene-dependent. This parameter can be mapped with a texture. It is recommended that you use a 3D texture for the purpose. 

Multiplier – The strength of the absorption effect. Smaller values reduce the effect, making the material more transparent. Larger values increase the effect, making the material more opaque.

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Refraction

Dispersion Abbe. – Allows the user to increase or decrease the dispersion effect. Lowering it widens the dispersion and vice versa.

Absorption

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).

Translucency

Mode – Selects the algorithm for calculating translucency (also called sub-surface scattering). Note that refraction must be enabled for this effect to be visible. Currently only single-bounce scattering is supported.

None – No translucency is calculated for the material.
Hard (wax) model – This model is specifically suited for hard materials like marble.
Soft (water) model – This model is mostly for compatibility with older V-Ray versions (1.09.x).
Hybrid model – This is the most realistic SSS model and is suitable for simulating skin, milk, fruit juice and other translucent materials.

Color – Normally the color of the sub-surface scattering effect depends on the Absorption color; this parameter allows you to additionally tint the SSS effect.

Scatter Coeff. – The amount of scattering inside the object. A value of 1.0 means 0 means rays will be are scattered in all directions; 0.0 means a ray cannot change its direction inside the sub-surface volume.

Backwrd/Fwd Coeff. – Controls the direction of scattering for a ray. A value of 1.0 means a ray can only go forward (away from the surface, inside the object); 0 0.5 means 5 means that a ray has an equal chance of going forward or backward; 0.0 means a ray will be is scattered backward (towards the surface, to the outside of the object).

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

Advanced Options

Show advanced Options – Enabling this option exposes some advanced options in this tab.

Dive to Surface Node – Press this button to dive into the Complex Material network of nodes and selects the Surface Node.

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Diffuse/Self-Illum./Bump/Reflection/Reflection Glossiness/Refraction/Refraction Glossiness/ Displacement – Each of these channels can have a texture map assigned and controlled from this tab. The drop down menu activates a field where you can specify how to control its settings.

From Tab – The value for the parameter is taken from its tab settings.
Image File – Activates the image field, so you can attach an image file.
Vector/Float Attr. – Activates the last field for the parameter, where you can specify an attribute to control the parameter's settings.
Disabled (Only for Bump and Displacement) – Bump and Displacement can either be used with an image file or stay disabled.

Viewport Display Options

Display Diffuse Texture – Enable to make the diffuse texture visible in the viewport.

Display Custom Channel – Specifies the UV attribute name that Houdini uses to map the texture in the viewport.

Display Reflections – Enables a rough representation of the reflection in the viewport, taken only from the Reflection tab.

Display Transparency – Enables a rough representation of the refraction in the viewport, taken only from the Transparency tab.

Display Displacement – Enables a representation of the displacement in the viewport, displaying also the Amount and Shift values from the tab.

Display Custom Channel – This option can show any of the specified textures in the viewport. You have to include the relative path to the texture in order to see it.

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Roughness/Reflect IOR/Aniso. Strength/Aniso. Rotation/Metalness/Refraction IOR/Absorption/Translucency – Each of these channels can have a texture map assigned and controlled from this tab. The drop down menu activates a field where you can specify how to control its settings.

From Tab – The value for the parameter is taken from its tab settings.
Image File – Activates the image field, so you can attach an image file.
Vector/Float Attr. – Activates the last field for the parameter, where you can specify an attribute to control the parameter's settings.

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UVs

From this panel you can control how the texture mapping is executed.

UVs Type – Specifies whether to use the geometry's UV mapping (Use Geometry UV's) or the projection (Use Projection) to generate the UVs.

Projection Type – This option is available only when the UVs Type is set to Use Projection. Specifies the type of projection mapping to use from the following:

None 
Planar 
Spherical 
Cylindrical
Ball 
Cubic 
Triplanar 
Perspective

UV Attribute Name – Specifies the name of the UV attribute.

Repeat UV – Specifies the number of times to repeat the texture in the U / V direction.

Offset UV – Specifies an offset for the U / V position.

Noise UV – Specifies the amount of noise to add.

Rotate UV – Specifies a rotation amount in UV space.

Wrap U/V – Enables texture wrapping in the U / V direction.

Mirror U/V – Enables texture mirroring in the U / V direction.

Stagger – Enables texture staggering.

Advanced Options

Show advanced Options – Enabling this option exposes some advanced options in this tab.

Dive to UV Node – Press this button to dive into the Complex Material network of nodes and selects the UV Node.

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Main

Texture Type – Specifies the mode in which the displacement will be is rendered.

Normal – Takes the original surface geometry and subdivides its triangles into smaller sub-triangles which are then displaced. It can be applied for arbitrary displacement maps with any kind of mapping.
2D – Bases the displacement on a texture map that is known in advance. The displaced surface is rendered as a warped height-field based on that texture map. The actual raytracing of the displaced surface is done in texture space, and the result is mapped back into 3D space. The advantage of this method is that it preserves all the details in the displacement map. However, it requires that the object have valid texture coordinates. You cannot use this method for 3D procedural textures or other textures that use object or world coordinates. The displacement map can take any values. 
Vector – If using a displacement texture that is not grayscale, V-Ray converts it to grayscale before rendering the displaced geometry. This mode allows V-Ray to use the Red, Green, and Blue channels of the displacement texture to displace the geometry in the U and V directions in addition to the direction of the face normal.
Vector (Absolute) – A vector-type displacement mode in which the texture is interpreted as 0.5-based tangent space displacement map.
Vector (Object) – Only meaningful, if a VRayPtex texture is used for displacement, where the texture values represent 0-based displacement in object space. If mesh information is stored in the Ptex file, V-Ray can also displace correctly mesh deformations.

Amount – The amount of displacement for white areas of the displacement map. If Use Global Settings is enabled, this value is multiplied by the global displacement Amount option.  A value of 0.0 means the object appears unchanged. Higher values produce a greater displacement effect. This can also be negative, in which case the displacement pushes geometry inside the object.

Shift – Specifies a constant which will be is added to the displacement map values, effectively shifting the displaced surface up and down along the normals. This can be either positive or negative.

Water Level – Geometry below this displacement level threshold will be is clipped away. This can be used for clip mapping a displacement map value below which geometry will be is clipped. 

Options

Flip Green/Blue – When enabled, the Green and Blue channels of the supplied texture map will be are swapped. 

Use Bounds – When enabled, allows the user to set the minimum and maximum values for the displacement texture. 

Min/Max Bound – These two options allow you to specify custom boundaries for the displaced geometry when Use Bounds is enabled. By default is limited to values between 0 and 1.

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Shift –Specifies a constant which will be is added to the displacement map values, effectively shifting the displaced surface up and down along the normals. This can be either positive or negative.

Options

Keep Continuity – When enabled, V-Ray produces a connected surface. Use it when you get splits (usually around sharp edges) in the displaced geometry. 

Cache Normals – When enabled, V-Ray generates and saves information about the normal of each newly generated vertex. This requires additional memory but speeds up the shading calculations during rendering.

Use Global Settings – When enabled, the global Displacement quality settings from the V-Ray Renderer are used.

View Dependent – Determines if view-dependent tessellation is used.  When enabled, Edge Length determines the maximum length of a subtriangle edge, in pixels. A value of 1.0 means that the longest edge of each subtriangle will be is about one pixel long when projected on the screen. When  View-dependent  is off, Edge length  is the maximum subtriangle edge length in world units.

Edge Length – The maximum length of a subtriangle edge after subdivision. This affects the degree of subdivision before displacement, which in turn affects the quality of the displacement itself. Each triangle of the original mesh is subdivided into a number of subtriangles. More subtriangles mean more detail in the displacement, slower rendering times and more memory usage. Less subtriangles mean less detail, faster rendering and less memory used. Units used for this parameter depend on the View Dependent parameter.

Max Subdivions – Controls the maximum number of subtriangles generated from any one triangle of the original mesh. The square of this value is used. For example, a value of 256 means that at most 256 x 256 = 65536 subtriangles will be are generated for any given original triangle. It is recommended that this value not be increased a great deal over the default value of 256. If you need to use higher values, it is better to first tessellate the original mesh itself into smaller triangles before starting the displacement process.

Render As Subdivisions – When enabled, the object is subdivided during rendering.

Preserve Map Borders – Specifies how to handle subdivisions of UV coordinates at UV seams. The possible values are:

None – UVs are always subdivided regardless of whether they are on a UV seam or not
Internal – Only preserve UVs if they are on an internal UV seam;
All – Does not subdivide UVs on UV seams.

Classic Catmull-Clark – When this option is enabled, V-Ray uses the Classic Catmull-Clark method for subdividing the mesh instead of the hybrid one used by default. This option should be enabled only if the mesh is composed entirely of rectangular faces or it will does not work.

Advanced Options

Show advanced Options – Enabling this option exposes some advanced options in this tab.

Dive to Displacement Node – Press this button to dive into the Complex Material network of nodes and selects the Displacement Node.