VRayMtl

The VRayMtl is a very versatile material that allows for better physically correct illumination (energy distribution) in the scene, faster rendering, and more convenient reflection and refraction parameters. This material can be easily set up to simulate a huge variety of surfaces from plastics to metals to glass and more by adjusting a handful of parameters.

Furthermore, with the VRayMtl you can apply different texture maps, control the reflections and refractions, add bump and displacement maps, force direct GI calculations, and choose the BRDF for how light interacts with the surface material.

^{Image courtesy of Mathew Monro}

||Hypershade|| > Create panel > VRay section > VRay Mtl

||Create Render Node window|| > VRay section > VRay Mtl

||V-Ray Shelf|| > Right-click to Create V-Ray Materials button > VRay Mtl

This section allows you to control the swatch for the VRayMtl material.

Auto update – When enabled, the view in the swatch will update automatically every time one of the VRayMtl properties is changed. When the check box is not selected the swatch will not update automatically but you will be able to update it manually with the Update button.

Max resolution – Determines the maximum resolution of the swatch.

Update – When clicked, forces an update of the swatch.

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

Amount – A multiplier for the diffuse color.

Opacity Map – Assigns opacity to the material where white is completely opaque and black is completely transparent. You can also assign a map by clicking the check board button. This way you can create a material that has a non-uniform opacity.

Opacity mode – Controls how opacity is sampled. For more information, see the Opacity mode parameter example below. This parameter is not available when the renderer is set to GPU.

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.

Roughness Amount – Used to simulate rough surfaces or surfaces covered with dust (for example, skin, or the surface of the Moon). This parameter is not available when the renderer is set to GPU.

Self-Illumination – The self-illumination color of the material. A texture map can be used for the self-illumination color by clicking on the check board box next to the color slider.

Self-Illumination GI – When enabled, the self-illumination affects global illumination rays and allows the surface to cast light on nearby objects. Note, however, that it may be more efficient to use area lights or VRayLightMtl material for this effect. 

Compensate Exposure – When enabled, the intensity of the Self-Illumination will be adjusted to compensate the exposure correction from the VRayPhysicalCamera.

Slide to change the Opacity mode.

The BRDF parameter determines the type of the highlights and glossy reflections for the material. This parameter has an effect only if the reflection color is different from black and reflection glossiness is different from 1.0.

BRDF Type – Determines the type of BRDF (the shape of the highlight). For more information, see The BRDF Type example below.

Phong – Phong highlight/reflections. Specular highlights have a bright center with no falloff.
Blinn – Blinn highlight/reflections. Specular highlights have a bright center with a tight falloff.
Ward – Ward highlight/reflections. Specular highlights have a bright center with a falloff broader than Blinn, but tighter than Microfacet GTR (GGX).
GGX – GGX Microfacet highlight/reflections. Specular highlights have a bright center with a longer falloff.

Slide to change BRDF type.

Example: Reflection Color

This example demonstrates how the Reflect 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).

Example: Fresnel Option

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 Reflect color is pure white (255, 255, 255).

Example: Reflection Glossiness

This example demonstrates how the Glossiness parameter controls the highlights and reflection blurriness of the material. Fresnel IOR = 3.5.

Example: Reflection Depth

This example demonstrates the effect of the reflection Max depth parameter.

Anisotropy – Determines the shape of the highlight. A value of 0.0 means isotropic highlights. Negative and positive values simulate "brushed" surfaces. For more information, see The Anisotropy Parameter example below. 

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). For more information, see The Anisotropy Rotation Parameter example below. 

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 assign a UVW Generator for the anisotropy effect.

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

Anisotropy UV Coords – Allows the user to assign a placement Texture node and change its UV coordinates to control the direction of stretching of the highlights.

Trace Reflections – Check this option to enable reflections for the material.

Reflection Exit Color – If a ray has reached its maximum reflection depth, this color will be returned without tracing the ray further.  

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. See the Reflection Depth example above for illustration.

Dim distance On – 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 will not be traced.

Dim fall off – A fall off radius for the dim distance.

Reflect On Back Side – When disabled, V-Ray will calculate reflections for the front side of objects only. Checking it will make V-Ray calculate the reflections for the back sides of objects too.

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

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

Color Only – The reflectivity will affect 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 will be affected by the reflectivity of the material.

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

Amount – This is the amount of the refraction color.

Refraction Glossiness – Controls the sharpness of refractions. A value of 1.0 means perfect glass-like refraction; lower values produce blurry or glossy refractions. Use the Subdivs parameter below to control the quality of glossy refractions. For more information, see The Refraction Glossiness Parameter example below.

Refraction subdivs – Controls the quality of glossy refractions. Lower values will render faster, but the result will be noisier. Higher values take longer but produce smoother results. This parameter is not available when the renderer is set to GPU.

Refraction 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 not change direction.  For more information, see The Refraction IOR Parameter example below.

Fog 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 fog 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. For more information, see the Fog Color Parameter example below.  

Fog multiplier – The strength of the fog effect. Smaller values reduce the effect of the fog, making the material more transparent. Larger values increase the fog effect, making the material more opaque. This parameter can be mapped with a texture. It is recommended to use a 3D texture for the purpose. For more information, see The Fog Color Parameter example below. 

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).

Affect Shadows – This parameter causes the material to cast transparent shadows to create a simple caustic effect dependent on the refraction color and the fog color. For accurate caustic calculations, disable this parameter and instead enable Caustics in the GI tab. Simultaneous usage of both Caustics and Affects Shadows can be used for artistic purposes but does not produce a physically correct result.

Example: Refraction Color

This example demonstrates the effect of the Refract color parameter to produce glass materials. For the images in this example, the material has a gray Diffuse color, white Reflect color, and the Fresnel Reflections option is enabled.

Example: Refraction IOR

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: Refraction Glossiness

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: Refraction Depth

This example demonstrates the effect of the refraction Max depth parameter. Note how too low of a refraction depth produces incorrect results. Also, in the last two examples, note how areas with total internal reflection are also affected by the Reflection Max depth.

Example: Fog Color

This example demonstrates the effect of the Fog color parameter. Notice that we are changing the hue value of the Fog color. 

Example: Fog Multiplier

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.

 On – Enables sub-surface scattering for the material.

Translucency Color – Normally the color of the sub-surface scattering effect depends on the Fog color; this parameter allows you to additionally tint the SSS effect. This parameter is not available when the renderer is set to GPU. 

Subdivs – Controls the quality of the subsurface scattering effect. Lower values will render faster, but the result will be noisier. Higher values take longer but produce smoother results. Note that this parameter is available for changing only when Use local subdivs is enabled in the DMC Sampler Settings. This parameter is not available when the renderer is set to CUDA.

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 will be scattered backward (towards the surface, to the outside of the object).

Scatter bounces – Controls how many times the rays will bounce inside the object.

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

Thickness – Limits the rays that will be traced below the surface. This is useful if you do not want or don't need to trace the whole sub-surface volume. See the Thickness example below for illustration.

Environment fog – When enabled, V-Ray traces direct lighting into the material.

Example: Thickness

This example demonstrates the effect of the Thickness parameter which limits the rays that will be traced below the surface. This is useful if the whole sub-surface volume does not need to be traced.

Trace Refractions – Enables refractions for the current material.

Refraction Exit Color on – When enabled and a ray has reached the maximum refraction depth, the ray terminates and the Refraction Exit Color value is returned. When this is off, the ray is not refracted but continues without changes.

Refraction Exit Color – If a ray has reached its maximum depth this color is returned instead of tracing the ray further.

Max depth – The number of times a ray can be refracted. Scenes with lots of refractive and reflective surfaces may require higher values to look correct. See the Refraction Depth example above for illustration.

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

Color Only – The transparency affects only the RGB channel of the final render.
Color+alpha – This will cause the material to transmit the alpha of the refracted objects, instead of displaying an opaque alpha. 
All channels – All channels and render elements are affected by the transparency of the material.

Dispersion – Enables the calculation of true light wavelength dispersion. 

Dispersion Abbe – Allows the user to increase or decrease the dispersion effect. Lowering it widens the dispersion and vice versa. See the Dispersion Abbe example below for illustration.

The Sheen layer can be used for creation of cloth material, such as satin.

Sheen Color – Specifies the color.

Amount – Specifies how much the sheen layer overlays the diffuse color. The higher the amount, the more of the sheen color you get. See the Sheen Amount example below for more information.

Sheen Glossiness – Controls the sharpness of reflections. A value of 1.0 means all of the light reaches the diffuse color, and when the value is smaller, the cloth material looks glossier. See the Sheen Glossiness parameter below for more information.

Example: Sheen Amount

This example shows how changing the amount of the sheen layer affects the material. Glossiness is set to its default value - 0.8. 

Example: Sheen Glossiness

This example shows how changing the glossiness parameter of the sheen layer affects the material. The Amount is set to its default value of 1

Map Type – Determines how the Map parameter is interpreted.

Map – Allows the user to select a texture for the bump or normal map. Leaving this unconnected turns off bump/normal mapping.

Note: When a texture with color corrections is used as a normal map, V-Ray will display a warning for unexpected results .

Bump Mult – A multiplier for the bump map effect.

Bump Shadows – When enabled, produces better looking shadows. It's recommended to keep this parameter disabled.

Bump Delta Scale – This parameter can be decreased to sharpen the bump and Increased to blur it.

Cutoff Threshold – A threshold below which reflections/refractions are not be traced. V-Ray tries to estimate the contribution of reflections/refractions to the image, and if it is below this threshold, these effects are not computed. Do not set this to 0.0 as it may cause excessively long render times in some cases. This parameter is not available when the renderer is set to GPU.

Double-sided – When enabled, V-Ray also shades the back-facing surfaces with this material. Otherwise, the lighting on the outer side of the material is always computed. This can be used to achieve a fake translucent effect for thin objects like paper.

Use Irradiance Map – When enabled, the irradiance map is used to approximate diffuse indirect illumination for the material. If this is off, brute force GI is used, in which case the quality of the brute force GI is determined by the Subdivs parameter of the Irradiance Map. You can use this for objects in the scene which have small details and are not approximated very well by the Irradiance Map. This option is ignored when the renderer is set to GPU.

Fix dark edges – When enabled, fixes dark edges that some times appear on objects with glossy materials.

This is the standard Maya hardware texturing rollout. It enables you to choose which texture connected to the VRayMtl will be displayed in the viewport and with what resolution.

It is recommended that you use a 3D texture for the purpose.