Using the Hair Gradient Material Shader

To connect the Hair Gradient Material shader

1. Open a Render Tree and choose Nodes Illumination Hair Gradient Material.

2. Attach the shader's output to the Surface and Shadow inputs on the hair object's Material node.

To edit the Hair Gradient Material shader

• Double-click the Hair Gradient Material node to open its property editor.

Setting the Hair's Diffuse and Ambient Colors

The hair's Diffuse color is its main color while the Ambient color is the hair surface's underlying ambient (shadow) color. This color gets modified by the scene's ambience. To get luminescent hair, use a high value for the Ambient parameter.

You can use the Diffuse/Ambient Blending Use Blend Gradient option to define the mixture of diffuse and ambient along the hair strand using a gradient slider.

With the Specular parameters on the Illumination page, you can set the color and area of falloff (decay) of Specular highlights on the hair. The specular color value should be very high for dark hair and very low for light hair.

For more information on each parameter on this page, see Illumination.

Setting the Hair's Transparency

Using the options on the Transparency page, you can set the transparency on the hair in different ways: the overall transparency, along the hair strand's length, or across the hair strand's width.

By tapering the transparency along the hair strand, you can improve the hair's overall look and reduce hair flickering. Reduced flickering gives a much smoother look, which is required for some furry animals, and also renders faster because you don't need to have high antialiasing settings to get rid of artifacts.

Another benefit of controlling the hair's transparency tapering in this shader is that you can leave the hair width value as a constant in the Hair property editor.

For more information on each parameter on this page, see Transparency.

Below, hair with higher transparency Length values at the tips.

Below, hair with lower transparency Length values at the tips.

Below, hair with higher transparency Cross values at the edges.

Below, hair with lower transparency Cross values at the edges.

Setting the Hair's Translucency

Translucency allows light to partially or diffusely pass through the hair strands. Using the Translucency options on the Indirect Illumination page, you can set the overall translucency for the whole hair strand or you can use the gradient slider to have varying translucency values along the hair strand. For example, hair is usually more translucent at the tips but less so at the roots.

Below, hair with high translucency values along most of the hair strand, then lessening at the root.

The Hair Gradient Material shader computes the illumination from both sides of the hair and adds the result. This lets you create a glow or rim lighting effect on hair, which can increase the realism of hair, especially when the hair is white or light-colored or in a brightly lit environment.

For more information on the Translucency parameters, see Indirect Illumination.

Setting the Effect of Indirect Illumination on the Hair

The parameters on the Indirect Illumination page let you control how global illumination, caustics, and final gathering affect the hair.

To control the effect of indirect illumination on the hair, set the value for the Radiance parameter. This controls the color and intensity (strength) of any indirect lighting effect over the hair's surface.

The color that is received on the hair from final gathering is multiplied by the color value you set here and then added on top. Be aware when you're setting this value that hair is very sensitive to final gathering because it's like thousands of tiny objects blasting color at each other in a short distance.

If you keep this value low for the hair, you can then associate an inclusive light for only the hair for shadows. This light should be quite dark so that it doesn't change the final gathering look. You can then exaggerate the specular of the hair so that it shines more from the dark light. You may also need to use negative umbra values to get dark enough shadows because of the dark light.

You can also connect a texture map to this parameter to reveal indirect illumination on a specific location of the hair.

For more information on the parameters on this page, see Indirect Illumination.

Adding Incandescence to the Hair

Incandescence is the emission of light from a hot body due to its temperature. This is often used to make objects look radiant, as if they are glowing or backlit. You can set the Incandescence parameters on the Indirect Illumination page to create a glow on either the hair strand's edges (rim) or its inner part (core). These parameters add an emissive color to the hair strand on top of the hair shading. You can use these parameters to improve the hair's look or add a special type of effect.

Hair appears to be more "tubular" when a light color is used on the inner core of the hair strand and a darker color is used on the edges (rim) of the strand.

With a light color used on the rim, you can create the effect that the hair is lit from behind.

On the top, incandescence is on the inner part of the hair strand.

On the bottom, incandescence is on the rim of the hair strand.

For more information on the Incandescence parameters, see Indirect Illumination.