by Hammer Chen
(3D model kindly provides by Lien Ying-Te)
1. two layers of materials. One provides SSS effect, another add highlight and reflection on top.
2. SSS layer: For the Diffuse I use gray color but can be black color. Less Fog color value, the results will be more contrasty (i.e., -1). The hybrid model will mimic the effect when thinner, more gloss; thicker less glossy looking. Fwd/bck coeff control the ratio of "fog color" and "Back-side color".
3. Highlight layer