V-Ray Hair Next Material is specifically designed for rendering hair and fur and provides settings for a workflow based on the physiology of real hair. Instead of tweaking arbitrary colors that mix together, the new Hair Next material uses a simple melanin slider that determines the hair color, just like in the real world. The material is the product of research based on the paper A Practical and Controllable Hair and Fur Model for Production Path Tracing.

Melanin – The pigmentation component that gives the hair strand its main color. The higher the value assigned, the higher the concentration of melanin and the darker the hair strands are. An integer node can be connected to control this parameter. See the example.

Pheomelanin – The redness (pheomelanin content) of the hair strand is a fraction of all melanin. 1.0 makes the hair redder. The ratio of melanin to pheomelanin determines how red the hair is. The pheomelanin amount has no effect if the melanin is set to 0. An integer node can be connected to control this parameter. See the example.

Dye Color – Applies a color tint to the hair. For a dyed hair look, set the melanin to 0; otherwise, the melanin darkens the dye color, and pheomelanin introduces redness to it. White means no hair dye. A color node can be connected to control this parameter.

Transparency – Controls the transparency of the hair. White is fully opaque, while black is fully transparent. A color node can be connected to control this parameter.

Diffuse Color – Controls the diffuse component of the shader. Use this for materials made out of cloth threads or other non-translucent fibers, as well as for dirty hair. A color node can be connected to control this parameter.

Diffuse Amount – Specifies the amount for the diffuse component of the material. An integer node can be connected to control this parameter.

Glossiness – Controls the glossiness along the hair strand. It primarily controls the width of the highlight, essentially how shiny the hair appears. An integer node can be connected to control this parameter.

Primary Glossiness Boost – Additional scaling factor to boost the primary reflection glossiness. This can be useful for reproducing the effect of shiny coating on rough-looking fur. An integer node can be connected to control this parameter.

Softness – Controls the overall softness of the hair by how much the highlights are wrapped around the individual hair strands. Higher values make the highlights wrap almost completely around the strands, giving the hair a smoother look, while lower values make it look crisper. An integer node can be connected to control this parameter. See the example.

Highlight Shift –  Shifts the highlights along the hair strand. Positive values shift the highlight away from the root of the hair, while negative values move the highlight closer to the root. Values in the range 2-4 are typical for human hair. An integer node can be connected to control this parameter. See the example.

Ior – The hair's index Of Refraction. The typical value for human hair is 1.55. The higher the value, the more reflective the hair strands. An integer node can be connected to control this parameter. See the example.

Example: Melanin

The pigmentation component that gives the hair strand its main color. The higher the value assigned, the higher the concentration of melanin, the darker the hair strands are. In the example below, Pheomelanin is set to 0. 

Example: Pheomelanin

The redness (pheomelanin content) of the hair strand as a fraction of all melanin. A value of 1.0 makes the hair redder. The ratio of melanin to pheomelanin determines how red the hair is. The Pheomelanin amount has no effect, if Melanin is set to 0. In the example, Melanin in set to 0.4.

Example: Softness

Controls the overall softness of the hair by how much the highlights are wrapped around the individual hair strands. Higher values make the highlights wrap almost completely around the strands, giving the hair a smoother look, while lower values make it look crisper. Melanin is set to 0.4.

Example: Highlight Shift

Shifts the highlights along the hair strand. Positive values shift the highlight away from the root of the hair, while negative values move the highlight closer to the root. In the example below, Melanin is set to 0.6.

The Glint rollout provides control over the Glint (focused highlight) and the Glitter (focused colorless highlight) parameters.

Glint Strength – Controls the strength of the colored highlights across and along the strand. See the Glint Strength example for more information.

Glint Variation – Adds a random glint variation along the strand. It affects the glint strength and orientation, the original secondary highlight strength and orientation, the softness, glossiness, and highlight shift. See the Glint Variation example for more information.

Glitter Strength – Controls the glitter strength. Glitter is the additional, more focused colorless highlight, which is randomly scattered along the strand. It is more pronounced with hard lighting, produced by small or collimated light sources. See the Glitter Strength example for more information.

Glitter Size – This parameter controls the size of the randomization pattern applied. Increasing the value increases the size of the pattern. See the Glitter Size example for more information.

Glint Scale – Internally, the variation along the strand is set in real-world units. This parameter allows correction of the appearance of hair, which is not modeled in real world scale. Values below 1.0 shrink the variation pattern, while values above 1.0 elongate it. See the Glint Scale example for more information.

Example: Glint Strength

Controls the strength of the highlights along and across the hair strand. Melanin is set to 0.6, and all other parameters are set to their default values.

Example: Glint Variation

The Glint Variation randomizes the glint effect along the strand. Melanin is set to 0.6, and all other parameters are set to their default values.

Example: Glitter Strength

Controls the strength of the glitter highlights. The higher the value, the more pronounced the effect. Melanin is set to 0.6, and all other parameters are set to their default values.

Example: Glitter Size

The Glitter Size controls the size of the randomization pattern applied. The higher the value, the more variation. Glitter Strength is set to 1, and all other parameters are at their default values.

The Randomization parameters can be used to introduce variation of the general parameter values. When using randomization, different hair strands receive slightly different values for the below parameters, so in fact, the randomization works on a per-strand basis.

Random Melanin – Adds variation to the amount of Melanin in each hair strand.

Random Dye Hue – Adds variation to the hue component of the Dye Color. This makes each strand appear with a different dye color. This parameter has no effect when Dye Color is not used, i.e., when Dye Color is pure white.

Random Dye Saturation – Randomizes the saturation of the Dye Color between hair strands. This makes each strand appear with a more or less saturated Dye Color. This parameter has no effect when the Dye Color is not used, i.e., when the Dye Color is pure white.

Random Dye Value – Adds variation to the value component of the Dye Color. This makes each strand appear with a brighter or darker Dye Color. This parameter has no effect when the Dye Color is not used, i.e., when the Dye Color is pure white.

Gray Hair Density – Adds variation to the number of gray hair strands. You can also assign a texture map to this parameter to specify areas where the density is higher.

Random Glossiness – Randomizes the Glossiness of each hair strand.

Random Softness – Assigns a random value for the Softness parameter for each strand. This makes some hair strands appear crisper, while others appear softer.

Random Highlight Shift – Adds variation to the Highlight Shift for each strand. This offsets the highlights closer or further away from the root of the hair on a per-strand basis.

Random Ior – Randomizes the IOR value for each hair strand. This makes some strands more reflective and others - less reflective.

Random Tangent – Adds a random offset to the hair Tangent. This makes the hair stands receive light from slightly different directions, which also means that the highlights are placed in slightly different places for each strand. Note that this parameter depends on the scene scale.

Primary Tint – The color tint for the primary component. Corresponds to the light reflected off of the outer surface of a hair strand. A color node can be connected to control this parameter. See the Primary Tint example for more information.

Secondary Tint – The color tint for the secondary component. Corresponds to the light piercing through and reflecting off of the back surface of a hair strand. A color node can be connected to control this parameter.

Transmission Tint – The color tint for the transmission component. Corresponds to the light going through the hair strands. A color node can be connected to control this parameter.

Trace Depth – The number of indirect bounces used to compute the effect of the multiple scattering. It can significantly affect the hair appearance, especially for light-colored hairs. The number of bounces necessary can vary from 5 for dark-colored hairs to 30 and more for light-colored ones.

Subdivs – Determines the number of subdivisions done when calculating the scattering.

Compensate Energy – When enabled, compensates for a lack of light bounces in areas where the hair is denser, and light cannot pass sufficiently.