This hair shader is based on Kajiya-Kay lighting model. The hair shader has a good approximation to represent specular, self shadow, back lit(rim light) and colors. And the specular and shadow can react to both of light direction and camera direction:
This picture clearly shows the specular effects and “volumetric feeling” due to the self shadowing. And also I unified the normals across each hair card, so it’s hard to tell the feeling of “hair cards”:
Because this shader used dithered alpha blending, the shader is using mask blending mode, so the overall shader is not that expensive and also maintained good blending of the hair tips.