Let me clarify. Realistic Hair reflection are in Marschner-style (primary spec shift away from root. 2ndary spec shift towards to the root relative to its primary spec shift). However in Arnold hair shader has already embedded with the shift and its shift relation. But custom spec shift parameter are added for user…
A lot of hair shader in most of the render engine has an attribute for shifting the specular. eg: https://support.solidangle.com/display/NodeRef/hair#hair-spec_shift Why do we want to shift the hotspot of the hair away compare with other materials. I thought the angle of reflection always have the same relation with the…