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Comment: wikit macro-replace (build 4280ad5-2021.10.08.115947) run by cwalker
Note

Do you need help rendering Xgen hair? Tutorials coming soon!Try this example file for Maya.

XgenExample.zip
Info

You can find an easier way to shade and control hair using a pattern included with RenderMan: PxrHairColor

 

 

PxrMarschner HairImage Modified
© Disney/Pixar

PxrMarschner is a material designed to render realistic hair, fur, and fibers.

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Diffuse Parameters

There are two choices of diffuse models: Zinke and Kajiya. By default, it is set to Zinke diffuse model which is for bidirectional scattering. See Importance Sampling for Physically-Based Hair Fiber Models.

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This is the diffuse color of the hair itself. Even for blond hair this is a darker shade than other color parameters for most realistic hair. For the best realism we recommend this be the same color as your Secondary Specular Color and adjust the gain alone. The default is middle grey.

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Specular Parameters

The bulk of your controls can be found under the Specular Parameters. Each of these relates in some way to the description below.

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Note

The Specular Gain controls allow the artist to break energy conservation for artistic purposes. If the values entered add to greater than 1.0 then the hair is not energy conserving. This is only important if you are unsatisfied with the look (it's too "hot") or are interested in starting with physically realistic shading.

Info

The default gain is now 1.0, previous versions may have been set to 0.33.

 

 

Primary Specular Gain

Gain for the R lobe of Marschner specular. This is like a clearcoat where the specular is fairly sharp and glossy and normally not colored. This specular is a direct reflection which is not tinted by any volume attenuation. Modifications of the R lobe help to make a hair look "wet" as well.

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Secondary Specular Gain

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Glint Gain

Gain for glints. This is a multiplier for the effect of Glints and operates like the other gain controls.


 

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primarySpecularColor
primarySpecularColor

Primary Specular Color

Specular color for tinting the Primary Specular (the R lobe). For natural hair and fur, this should always be white.


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Specular Offset

Cone offset in degrees, this can be used to shift the specular result along the hair.

 

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Refractive Index

The refractive index (ior) of the hair. Higher numbers increase the specularity similar to how this would work on opaque surfaces. This can make for an almost metallic looking hair fiber.

 

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Fresnel Mix

This control is to balance the fresnel energy attenuation along the hair. 

 

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Glint Width

This parameter smooths the Secondary Specular (TRT) and Glints distribution. This value should typically remain between 10 and 25 for realistic hair.

 

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Eccentricity

This is the cross-section aspect ratio of the hair and is usually between 0.85 and 1.0 for realistic hair. This is most often used when rendering curly hair. (Note this depends on the hair normals.)

 

Glow

Glow can be used to create hair fibers that appear to emit light or "glow" in the scene. 

Gain

Glow gain or weight. Below we go from the typical black hair and increase the gain (using white color) to 0.5 and then 1.0.


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Color

Controls the incandescence color, or glow, of the material. Below are various examples of textured inputs to the Color parameter.


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Globals

This section provides global controls for the entire material. Presence is also a global parameter that will mask out or "cutout" all the lobes as-if the object isn't present where the mask has a value of 0.0


Specular Energy Compensation

This control allows the darkening of the diffuse result as energy is taken by the specular response with leftover energy used to light the diffuse lobe. Setting this to 1.0 corresponds to the physical effect. The default is off (artistic control) and does not conserve energy.


Presence

Connect a mask here to apply a cutout pattern to your object. Presence is defined as a binary (0 or 1) function that can take on continuous values to anti-alias the shape. Useful for cutouts like creating leaves and other thin, complex shapes.

This value should be either 0 or 1. A value between 0 and 1 will produce unwanted noise!

 

Eccentricity Direction

This parameter can be used to override the geometric normals for controlling the Eccentricity parameter.

 

Shadow Color

Specify shadow color. This parameter is useful for faking a shadow color for art direction purposes.

 

Expand
titleNamed Lobes

Below are the named and user lobes from PxrMarschnerHair.

Named Diffuse Lobe

  • HairDiffuse

Named Specular Lobes

  • HairSpecularR
  • HairSpecularTT
  • HairSpecularTRT
  • HairSpecularGLINTS

User Lobes

  • HairAlbedo
  • HairTangent
  • Position