Reply To: Beer Lambert Absorption Group
HI Ali @Aliserhan ,
That’s a great question!
The definition of the Ray Length is what’s important here; the Blender Manual says: “Distance traveled by the light ray from the last bounce or camera.”
So we are not talking about one single Ray and it’s Length, but the Length of every (relevant) Ray.
By Multiplying the Ray Length by Backfacing, the Length of the yellow Ray in the image below, becomes 0 and the green Ray gets to keep its Length:
Does that help?