Subsurface Material Receiving Scatter If Opacity Is Low Even In Dark Room.

[Fairchild]

I have a sub surface shading material that will receive lighting from nearby light sources even if they are completely blocked off IF the opacity is low enough on the material.

In the example below I have a material with a subsurface profile and opacity set to 0.2

In the first picture a bright spotlight is shining through an open door. In the second picture the door is closed and the room is completely dark, but the subsurface material is oddly bright. This brightness goes away if I raise the opacity above ~0.6

[Hydrochen0118]

Determine the distance that the light traveled through the subsurface object;

This assumes that anything between this subsurface pixel and the light was also a subsurface material.
As a result, subsurface materials receive leaked light based on how transparent they are