Hair

This shader is considered deprecated and will be removed in a future release. You should use the Standard Hair shader instead.

 


Image credit to Pascal Floerks (rollover image)


The Hair shader is designed to render the look of hair or fur. Note that this shader needs to be used on geometry that has been defined to look like hair or fur (for example using Arnold's curves shape node). Other shaders such as Lambert could be used, but the Hair shader has a specular shading model specifically designed for thin hair fibers and lets you define different diffuse colors for the root and tip of the hairs, for example. This shader currently uses a simple Kay-Kajiya shading model.

Further examples of customer work using the Hair shader can be found here.

To render multiple hair curves using the same hair shader, it is far easier to create an override set. Tutorials on how to render curves can be found here.

 

The shader is divided into diffuse and specular tabs, more info on which can be found below. 

Matte

The matte option enables you to create holdout effects, by rendering the alpha as zero.

Opacity of the hair. This is set to full white by default, which means fully opaque hair. Playing with this value to make the hair less opaque (or in other words, more transparent) can sometimes help make the hair look softer, at the expense of increased render times. If not set to full white, be sure to have the Opaque flag off in the Arnold Parameters property of the hair object, or else Arnold will bypass any transparency-related calculations to optimize render times.

 

Workflow

  • First create an Ai Hair shader within the Hypershade window.
  • Select the hair system and open its Arnold attributes in the attribute editor.
  • Middle drag the Ai Hair node onto the Hair Shader slot.
  • Click on Override Hair in order to enable it.

Visible in Reflections/ Refractions is disabled by default for Maya hair. You must enable it in the Render Stats of the hairSystemShape.

Middle drag the Ai Hair node onto the 'Hair Shader' slot in the Arnold attributes of the hair


The controls are split into groups for Diffuse and Specular


The images below show the separate effect of the root, tip and specular colors. The far right image is the resulting combination of these colors.

 

Motion blur

When rendering hair with motion blur, the hair must first be cached, otherwise you will get incorrect results. The animation below shows the results of rendering with and without hair caching (rollover mouse to view the animation).

Left: Cached hair (motion blur renders correctly). Right: Hair without cache (motion blur renders incorrectly). Rollover mouse to view the animation.