_{Hair groom by Sohrab Esfehani}

Standard Hair is a physically-based shader to render hair and fur, based on the d'Eon model for specular and Zinke model for diffuse. Realistic results can be obtained by setting a few simple parameters for the base color, roughness, and index of refraction.

The Standard Hair shader is designed to be used with Arnold's curves shape node, and will not work well on other types of shapes. Other shaders like Lambert also work on curves, but cannot accurately simulate hair scattering.

When rendering hair, it is recommended that you use curves in Ribbon mode. Thick mode is meant for special effects such as tentacles, spaghetti, etc, and non-transparent shading.

• Texturing Hair
• Ramp Implicit UVs

Texturing Hair

When connecting textures to hair, the intended workflow is to set Melanin to 0 and link the texture to the Base Color. Diffuse can normally be left at 0. The Base Color will affect the secondary specular and transmission, just like Melanin. They are just two different ways to control the absorption in hair. Melanin can be seen as a way to more easily pick a Base Color appropriate for human hair, but if you have a texture, then Melanin can be disabled.

It is not possible to directly map hair shader parameters to Standard Hair, due to the very different shading models. The specular, specular2, and transmission colors are still separately controllable but are now automatically energy-conserving using Fresnel and need to be made brighter to get a similar look. The diffuse component needs to be made brighter to match hair. However, for accurate results, it is better not to use diffuse scattering or specular tints at all. These parameters provide artistic control beyond what is physically accurate and are usually not needed anymore.

To reduce noise with white/light-colored hair, you will need to either increase the Specular samples and/or the Camera (AA) samples.

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Ramp Implicit UVs

Implicit UVs on curves (root-to-tip) can be enabled in the Ramp.

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