Using the Geometry Hair Shader
With the Hair Geo shader, you can set the diffuse, ambient, and specular color shading and transparency for hair. All parameters in this shader have the option of using a gradient slider which allows you to have more accurate control of how the color shading and transparency occurs along the hair strand.
You can also add incandescence (glow) to the inner and outer hair edges. This creates a glowing appearance or makes the hair appear more “tubular,” which can improve the hair’s look or add the type of effect you want.
To connect the Hair Geo Shading shader
1. Open a Render Tree and choose Nodes > Hair > Hair Geometry Shading.
2. Attach the shader’s output to the Surface and Shadow inputs on the hair object’s Material node.
To edit the Hair Geo Shading shader
• Double-click the Hair Geo Shading 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.
To set the diffuse and ambient colors
• With both the Diffuse and Ambient colors, you can select the Use Diffuse/Ambient Gradient option to use a gradient slider. With both these color types, 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.
• If the Use Diffuse/Ambient Gradient option is off, you can use the regular color controls found with the color type.
To blend the diffuse and ambient colors
• Select Use Blend Gradient in the Diffuse/Ambient Blending area to define the mixture of diffuse and ambient along the hair strand using a gradient slider.
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 controls for all parameters, see Using the Gradient Controls.
|
Parameters in this property editor that have a connect icon For an example of using a texture map for colors, see Connecting a Texture Map to Hair Color Parameters. |
Setting the Hair’s Specular Color and Decay
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.
To set the specular color
• Select Use Specular Gradient in the Specular area to define the specular color along the hair strand using a 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.
• If the Use Specular Gradient option is off, you can use the regular color controls found with the color type.
To set the specular decay
• If the Use Specular Gradient option is off, you can set the Specular Decay to control the size and falloff of the specular highlights.
• When you select Use Specular Gradient, you can set the location and value of the specular decay along the length of the hair strand using the gradient slider for Specular Decay Root/Tip. The left end of the slider represents the hair strand root and the right end represents the hair strand tip.
Setting the Hair’s Transparency
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.
To set the basic transparency
• On the Transparency page, activate the calculation of transparency values by selecting Enable.
• Set the Overall Transparency, which is 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 (completely opaque) and 1 is 100% of either Length of Cross (whichever is active).
To set the transparency along the hair strand’s length or across its width
• Set the transparency along the hair strand’s length with the Length gradient controls. 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.
• Set the transparency across the hair strand using the Cross gradient controls. 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.
Setting the Hair’s 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. 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.
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.
To set the overall translucency
1. On the Indirect Illumination page of the Hair Geo shader, activate the calculation of translucency values by selecting Enable in the Translucency area.
2. Set the value for the Translucency slider, which is the translucency value of the whole hair strand. A value of 0 is no translucency (completely opaque) and 1 is full translucency.
To set the translucency along the hair strand’s length
1. Select Translucency Gradient in the Translucency area. This activates translucency using the gradient controls that appear.
2. Set the values with the gradient slider, which 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 controls, see Using the Gradient Controls.
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. You can also add incandescence (glow) to the inner and outer hair edges.
To control the effect of indirect illumination on the hair
• Set the value for the Radiance parameter in the Global Illumination / Caustics / Final Gathering area 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 texture map this parameter to reveal indirect illumination on a specific location of the hair.
To set incandescence on the hair
The parameters in the Incandescence area 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.
• Enable the Inner parameter and set its color values to add this color to the inner core of the hair strand. You can also control the Intensity of the incandescent color values. This lets you create glow effects and allows the hair to appear more tubular or prominent 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.
• Rim is the same as Inner except that it applies the incandescent color settings to the outer edges of the hair strand. With a light color used on the rim, you can create the effect that the hair is lit from behind.
The different gradient sliders in the Hair Geo Shading shader’s property editor let you adjust the parameter’s value using a gradient.
To select color markers
• Click a square marker below the gradient slider. You can then set its color using the color sliders or key its position to animate the color (see below).
To change the gradient composition
• Drag a color marker anywhere along the gradient.
To insert a color marker
• Click at any point along the gradient slider.
By default, the new marker assumes the color at that point in the gradient. You can use up to eight color markers, each with its own color.
To delete a color marker
• Right-click it and choose Delete marker or press Delete.
To change the blending between two colors
• Drag a round marker above the gradient slider closer to either square color marker.
Round markers appear between each pair of color markers, indicating the mid-point in the blend between those two colors.
To set the gradient’s interpolation
• Click the Cubic/Linear button to toggle 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.
1. Go to the frame at which you want to set keys.
2. Select a square color marker and click the Pos parameter’s animation icon.
To remove the animation on the markers
1. At any frame, select a square color marker and go to a frame where there is a key.
2. Click the Pos parameter’s animation icon to remove the key.
Autodesk Softimage v.7.5
beside them, as shown on the right, are mappable, meaning that you can connect texture maps to them to create specific effects.