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This parameter is a multiplier to the Diffuse Color. 0.0 means no diffuse color while 1.0 is the full affecteffect. The default is 0.0 which provides a very realistic dark to medium hair but with a potentially higher rendering cost. You may need to use higher amounts for lighter hair like platinum blond or grey hair.

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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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• Primary Specular: R is for "reflect" where the light hits the surface of the hair and reflects. This is the strong primary colorless specular.
• Secondary Specular: TRT is for "transmit", "reflect", and "transmit" where light transmits through the hair surface, then it reflects from inside the hair and exits the front of the hair. This is the secondary colored specular.
• Transmit Specular: TT is for "transmit" and "transmit" where light transmits into the hair surface and then exits through the other side. This is the colored transmission that responds to rim lighting.

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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 that 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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Cone angle (theta) for the TT lobe in degrees. The broader the angle, the softer and broader the highlight. Note that high gain for this parameter makes for soft and light-colored hair but generates quite a bit of noise. This may increase render times at higher angles.

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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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