Opaque Shadows – – When enabled, the hair material is always opaque for shadow calculations. This speeds up the rendering of transparent hair.
Opaque for GI – When enabled, the hair material is always opaque for GI calculations. This speeds up the rendering of transparent hair.
Simplify for GI – When enabled, 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 – Similar to the Use Irradiance Map option for the VRayMtl material; if it is disabled, the hair material is always calculated with brute force GI.
Light Multiplier – In the absence of GI, the hair may look very dark. GI is the proper way to correct this, but if GI must be really avoided, this multiplier can be used to brighten the hair.
