Light Collab / Help Documents / Hair Material Setup

Hair Material Setup
First create a vray material attribute for the hairSystemShape and connect a vrayHairMtl3 to it. Then in the HyperShade create a vrayHairSampler and connect it into the following inputs of your vrayHairMtl3:

  • diffuse color (needs 0.455 degamma)
  • secondary spec color (needs 0.455 degamma)
  • transmission color (no gamma correction)
The material works by combining diffuse color with primary spec (like in a typical material) as well as a second colored spec (augmenting the diffuse) and a "transmission" (to get light passing through the hair such as in rim lighting).

The above setup will pipe the nHair color, with randomization, into the vray material. In addition you can connect a texture map to the hair system color and export it to your hairMtl with the vrayHairSampler. the HairMtl does not work with the linear workflow button so you will need to pipe your color output through a gamma correction node set to 0.455. Note that the de-gamma is needed for the diffuse color, but NOT for the transmission color which should remain linear.

Optionally you can also connect the vrayHairSampler's distanceAlongStrand output into the vCord of a ramp texture and then input the ramp into the material's transparency to get tip fade (the ramp should be black at the bottom and white at the top for the tip, using an exponential falloff). If you opt to do this, you''ll probably want to uncheck "opaque for shadows" in the hairMtl attributes (see below). It is preferable however to do this with the hair system hair width graph as adding transparency to the material will increase the render time.

Set the following for the vrayHairMtl3 attributes (you can also make a preset for this):

    Diffuse:
  • Overall: 0.8
  • Diffuse amount: 0.1
    Primary Spec:
  • Primary spec: 0.5
  • Primary Amount: 0.01
  • Primary Gloss: 0.9
    Secondary Spec:
  • Lock secondary: off
  • Secondary amount: 1
  • Secondary gloss: 0.8
    Transmission:
  • Transmission Amount: 1
  • Gloss Length: 0.95
  • Gloss Width: 0.85
  • All check boxes on
    Checkboxes:
  • Opaque for shadows: ON. This speeds up the rendering of transparent hair.
  • Opaque for GI: ON. This speeds up the rendering of transparent hair.
  • Simplify for GI: ON. A simplified diffuse version of the BRDF is used for GI calculations. This may speed up the rendering of hair but may significantly change the final look.
  • Use cached GI: ON. When ON the IR map is used. If OFF this will force the hair to be calculated with brute force GI (BF/BF) even if the GI engine is set to IR. The subdivs for the brute force are then determined my the irradiance subvis. Since the default IR subdivs are 50 (while the default BF subdivs are 8) rendering BF/BF at 50 subdivs can be very slow. A better approach is to put the hair in a separate render layer and set the GI there.

  • Multimattes It is not currently possible to add a material ID attribute to the hairMtl. Instead an object ID can be added to the PFX transform node (not the shape).

    Refraction If you need to have the hair visible in refractions (through glass) this can be turned on in the PFXHairShape attributes. However this attribute is not visible in the attribute editor in Maya 2013. So you need to find it the attribute Spread Sheet and enable it there. (Oddly this option is in the PFXHair transform, but it has no effect. So apparently the wrong one was hidden).
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