Hair Gradient Material

Category: Illumination

Shader Family: Surface Material

Output: Color

Controls the diffuse, ambient, and specular RGB colors, transparency, and indirect illumination of hair objects using gradient sliders so that you have a high degree of control over where the shading occurs on the hair strand.

For an example of using a texture map for colors, see Connecting a Texture Map to Hair Color Parameters [Hair]. For other topics related to rendering hair, see Rendering Hair [Hair].

Name	The shader's name. Enter any name you like to give it a unique identity, which is especially useful when selecting hair elements.

Illumination

Diffuse

You can choose to use the regular color controls or gradient sliders to set the hair's Diffuse color.

Enable Diffuse Shading

Uses the diffuse color settings for the hair as defined with the regular color controls.

Use Diffuse Gradient

Uses the diffuse color set with the gradient slider that appears when you select this option.

If this option is off, you can use the regular color controls found when you select Enable Diffuse Shading.

Gradient Slider

The gradient slider determines the diffuse color value along the hair strand's length. The left end of the slider represents the hair strand root and the right end represents the hair strand tip.

For information on using the gradient sliders, see Using the Gradient Controls.

Ambient

You can choose to use the regular color controls or gradient sliders to set the hair's Ambient color.

Ambient color is weighted by the scene's global ambience.

Use Ambient Gradient

Uses the Ambient color settings for the hair as defined by the gradient slider that appears when you select this option.

If this option is off, the ambient color settings are defined with the regular color controls.

To get luminescent hair, use a high value for the Ambient parameter.

Gradient Slider

The gradient slider determines the ambient color value along the hair strand's length. The left end of the slider represents the hair strand root and the right end represents the hair strand tip.

For information on using the gradient sliders, see Using the Gradient Controls.

Diffuse / Ambient Blending

Use Blend Gradient

Uses the Blend color settings for the hair as defined by the gradient slider that appears when you select this option. This determines what percentage of the diffuse and ambient colors are used along the hair strand.

The left end of the slider represents the hair strand root and the right end represents the hair strand tip. A value of 1 means that both Diffuse and Ambient are visible, and a value of 0 means that only Ambient is visible.

Gradient Slider

Determines the diffuse and ambient color blend along the hair strand's length. The left end of the slider represents the hair strand root and the right end represents the hair strand tip.

A value of 1 means that both Diffuse and Ambient are visible, and a value of 0 means that only Ambient is visible.

For information on using the gradient sliders, see Using the Gradient Controls.

Specular

Enable	Enables the calculation of specular highlights and uses the Specular color settings for the hair as defined with the regular color controls.
Use Specular Gradient	Uses the Specular color settings for the hair as defined by the gradient slider that appears when you select this option. If this option is off, you can use the regular color controls found with the color type.
Gradient Slider	Determines the specular color value along the hair strand's length. The left end of the slider represents the hair strand root and the right end represents the hair strand tip. For information on using the gradient sliders, see Using the Gradient Controls.
Specular Decay	Controls the size and falloff of the specular highlights. This option is unavailable if you select the Use Specular Gradient option.
Specular Decay Root / Tip	When you select the Use Specular Gradient option, you can also set the location (root and tip) and value of the specular decay along the length of the hair strand using its own gradient slider. The left end of the slider represents the hair strand root and the right end represents the hair strand tip. The gradient is used as a weighting factor to modulate the hair root and hair tip shininess.

Transparency

Enable

Enables calculation of transparency values.

Overall Transparency

The transparency value of the whole hair strand. A value of 0 is no transparency (completely opaque) and 1 is completely transparent when Length and Cross are not active.

When either Length or Cross are active, a value of 0 is no transparency and 1 is 100% of either Length of Cross (whichever is active).

Length

Enable

Enables the calculation of transparency values along only the length of the hair strand.

Gradient Slider

The gradient slider determines the transparency value along the hair strand's length. The left end of the slider represents the hair strand root and the right end represents the hair strand tip. A value of 0 is completely opaque and 1 is completely transparent.

For information on using the gradient sliders, see Using the Gradient Controls.


On the left, hair with higher Length transparency values at the tips.	On the right, hair with lower Length transparency values at the tips.

Cross

Enable

Enables the calculation of transparency values across the hair strand.

Gradient Slider

The gradient slider determines the transparency value across the hair strand. The left end of the slider represents the hair strand edges (rim) and the right end represents the hair strand center (core). A value of 0 is completely opaque and 1 is completely transparent.

For information on using the gradient sliders, see Using the Gradient Controls.


On the left, hair with higher Cross transparency values at the edges.	On the right, hair with lower Cross transparency values at the edges.

Indirect Illumination

Global Illumination / Caustics / Final Gathering

Radiance

Used to control the color and intensity (strength) of any indirect lighting effect (global illumination, caustics, or final gathering) over the object'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.

Translucency

Translucency allows light to partially or diffusely pass through the hair strands. The Hair Geo shader computes the illumination from both sides of the hair and adds the result.

Enable

Activates the calculation of translucency on the hair.

Translucency

If you select Enable, you can use this slider to set the hair strand's overall translucency level. A value of 0 is no translucency (completely opaque), and 1 is full translucency.

Translucency Gradient

Activates translucency using the gradient controls. The gradient slider determines the translucency value along the hair strand's length. The left end of the slider represents the hair strand root and the right end represents the hair strand tip. A value of 0 is completely opaque and 1 is completely translucent.

For information on using the gradient sliders, see Using the Gradient Controls.

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

Incandescence

Adds an emissive color to the hair strand on top of the hair shading. This lets you create glow effects and allows the hair to appear 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.

Inner
Enable	Uses the incandescent color settings for the hair as defined with the color controls. This is applied to the inner core of the hair strand.
Color controls	Controls the R, G, B, and alpha values for the emissive color applied to the inner core.
Intensity	The intensity of the incandescent color values.

Rim

Enable	Uses the incandescent color settings for the hair as defined with the color controls. This is applied to the edges (rim) of the hair strand.
Color controls	Controls the R, G, B, and alpha values for the emissive color applied to the hair strand edges.
Intensity	The intensity of the incandescent color values.

Using the Gradient Controls

The different gradient sliders in the Hair Geo Shading shader's property editor let you adjust the parameter's value using standard gradient controls as described here.

A	Gradient slider displays how the color/alpha values change.
B	Selected square marker shows current color value in the color chip and the Pos (position) value. To delete a color marker, right-click it and choose Delete marker from the menu or press Delete.
C	Round markers indicate the mid-point of the blending (interpolation) between two square color markers. Moving the circle closer to either color marker causes less of that color, and more of the other, to appear in that "sub-gradient". The net effect is a sharper blend and a larger portion of the dominant color.
D	Current color value of the selected marker is displayed in the color chip. You can use the color sliders to set the color and alpha values for the marker. This affects the colors used in the gradient slider.
E	To change the gradient composition, drag a color marker anywhere along the gradient. Click in the gradient slider to add a square color marker at that point. You can add up to 8 color markers, each with their own color. By default, the new marker assumes the color of that point in the gradient.
F	Controls the position of the selected marker along the gradient slider. Square Color Markers: If a color marker is selected, the Pos value indicates its position, on a scale of 0 - 1, within the entire gradient. Circle Interpolation Markers: If an interpolation marker is selected, the Pos value indicates its position, on a scale of 0 -1, between its associated pair of color markers. You can animate the position of the markers by setting the values and clicking the Pos parameter's animation icon at different frames. To remove the animation on a marker, go to a frame where there is a key and click the Pos animation icon again. Cubic/Linear: Switches between linear and cubic interpolation of the gradient. Cubic interpolation results in a smoother transition between alpha values, while linear interpolation results in sharper transitions.

Render Tree Usage

This surface shader can be connected directly to the Surface and Shadow inputs of the Material node of a hair object. You can use textures to control color inputs (such as Diffuse or Ambient Color). Alternatively, you can attach an illumination shader such as Phong to the Hair Geo Shading's material input to replace the shader's own illumination calculations.

You could use an image shader or procedural shader to "texture" the hair. Or use the Scalar State shader to extract the hair length/crosswise information, which can then be regrouped into a vector (Scalars2Vector shader). This vector can then be used to lookup a procedural noise or image.