This is a fairly advanced concept describing light's effects on certain materials, commonly called subsurface scattering.
Most light reflects off of the surface of an object but some may also pass through, bounce around and depart in a scattered manner.
On the human figure it's most visible in the ears, nose, fingers and toes, throughout the thinner parts of the body. It's visible in many other materials too. Including grass, fruit, balloons, clouds, etc...
Nathan Aardvark
2016-01-26 17:35:54 +0000 UTCDouglas Kim
2016-01-26 13:28:20 +0000 UTC