Bump and Normal Mapping
A special material - the VRayMtl - is provided with the V-Ray renderer. This allows for better physically correct illumination (energy distribution) in the scene, faster rendering, more convenient reflection and refraction parameters. Within the VRayMtl you can apply different texture maps, control the reflections and refractions, add bump maps and choose the BRDF for the material.
This section allows you to control the swatch for the VRayMtl material.
Auto update - when this option is selected 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 button.
Max resolution - this parameter determines the maximum resolution of the swatch.
Update - click this to force an update of the swatch.
Diffuse Color - this is the diffuse color of the material. Note: the actual diffuse color of the surface also depends on the reflection and refraction colors.
Amount - this is a multiplier for the diffuse color.
Opacity Map - here you can assign 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.
Roughness Amount - this parameter can be used to simulate rough surfaces or surfaces covered with dust (for example, skin, or the surface of the Moon).
Self-Illumination - this is 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.
The BRDF parameter determines the type of the hilights 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.
BDFR Type - this determines the type of BRDF (the shape of the hilight):
Phong - Phong hilight/reflections
Blinn - Blinn hilight/reflections
Ward - Ward hilight/reflections
Reflection Color - reflection color. Note that the reflection color dims the diffuse surface color.
Amount - a multiplier for the reflection color.
Lock highlight and reflection glossiness - when this option is off you can enter different values for the Hilight glossiness and Reflection glossiness. However this will not produce physically correct results.
Hilight glossiness - this determines the shape of the hilight on the material. Normally this parameter is locked to the Reflection glossiness value in order to produce physically accurate results.
Reflection glossiness - controls the sharpness of reflections. A value of 1.0 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.
Reflection Subdivs - controls the quality of glossy reflections. Lower values will render faster, but the result will be more noisy. Higher values take longer, but produce smoother results.
Use Fresnel - checking 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.
Lock Fresnel IOR To Refraction IOR - allows you to unlock the Fresnel IOR parameter for finer control over the reflections.
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.
Trace Reflections - check this option to enable reflections for the material.
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.
Reflect On Back Side - when this option is not checked 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 - soften the edge of the BRDF at light/shadow transitions
Fix dark edges - enabling this option will fix dark edges that some times appear on objects with glossy materials
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.
Anisotropy - determines the shape of the hilight. A value of 0.0 means isotropic hilights. Negative and positive values simulate "brushed" surfaces.
Anisotropy UV coords - allows you to assign a placementTexture node and change its UV coordinates to control the direction of stretching of the highlights.
Anisotropy Rotation - determines the orientation of the anisotropic effect in degrees (rotation in degrees).
Refraction Color - refraction color. Note that the actual refraction color depends on the reflection color as well.
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.
Refraction subdivs - controls the quality of glossy refractions. Lower values will render faster, but the result will be more noisy. Higher values take longer, but produce smoother results.
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.
Fog color - 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.
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.
Fog bias - this parameter allows to change the way the fog color is applied; by adjusting this parameter you can make thin parts of the object to appear more transparent than normal, or less transparent than normal.
Trace Refractions - check this option to enable refractions for the current material.
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.
Affect shadows - this will cause the material to cast transparent shadows, depending on the refraction color and the fog color.
Affect Channels - Allows you to specify which channels are going to be affected by the transparency of the material
Color Only - the transparency will affect 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. Note that currently this works only with clear (non-glossy) refractions.
All channels - all channels and render elements will be affected by the transparency of the material
Dispersion - this option enables the calculation of true light wavelength dispersion
Dispersion Abbe - this option allows you to increase or decrease the dispersion effect. Lowering it widens the dispersion and vice versa.
Bump and Normal mapping
Map Type - this determines how the Map parameter is interpreted.
Map - this option allows you to select a texture for the bump or normal map. Leaving this unconnected turns off bump/normal mapping.
Bump Mult - this is a multiplier for the bump map 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.
Subdivs - controls the quality of the subsurface scattering effect. Lower values will render faster, but the result will be more noisy. Higher values take longer, but produce smoother results.
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 - this options 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 - this 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.
Environment fog - when this option is checked V-Ray will trace direct lighting into the material.
Cutoff Threshold - this is a threshold below which reflections/refractions will 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.
Double-sided - if this is true, V-Ray will flip the normals for back-facing surfaces with this material assigned. Otherwise, the lighting on the "outer" side of the material will be computed always. You can use this to achieve a fake translucent effect for thin objects like paper.
Use Irradiance Map - when this option is on, the irradiance map will be used to approximate diffuse indirect illumination for the material. If this is off, brute force GI will be used. You can use this for objects in the scene which have small details and are not approximated very well by the irradiance map.
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.