skin-shading

Skin that reads as skin without a subsurface pipeline: three cheap terms a material plugin adds to a PBR material, lit by the scene's sun. The character builder uses it on every body.

• Scatter: light wraps a little past the shadow line, reddened, the way light that went into skin comes out again beside where it went in. It softens the terminator, which is most of what makes a lit body look like painted plastic.
• Rim: a soft lift at grazing angles, the fine hair and oil on skin.
• Back-light: light from behind shows through the THIN parts (ears, the nose, fingers), reddened. Thinness is per vertex, worked out once from the mesh by skinThinness, and carried in the vertex colour's alpha. Babylon's own translucency needs a thickness texture, and without one it lit the whole back of a torso red.

skinShading(material, options) attaches it and returns the plugin, whose scatter, rim and backlight can be changed live. It reads the scene's first directional light each frame (or the sun you give it).