In Project 9, we were to add the Beere-Lambert Law to our renderer. The Beere-Lambert Law models the amount of light absorbed while traveling through a medium. Because different wavelengths are absorbed based on the distance they must travel through the medium, different colors can be absorbed causing different wavelengths to be more pronounced. Certain types of glass often absorb high and low wavelengths leaving a greenish tint at certain angles. Usually this effect can be seen when the light is going through the greatest distance of the glass. To compute the absorbtion at certain frequencies, euler's number e was taken to the exponent of the distance times a large negative constant (which changes based on the scene metrics).
In the picture below, five spheres are modeled. The back left sphere is a reflective sphere, while the back right is a diffuse sphere. Theses spheres are only to provide background to the scene. The spheres in front are used for comparison. The left sphere is a diffuse/reflective sphere with a purplish hue. The middle sphere is a translucent sphere that implements the Beere-Lambert Law based on the distance of the medium. This gives the sphere the slightly greenish tint. The sphere on the right is also a translucent sphere, but does not implement the Beere-Lambert Law. This was to show the difference in hues generated by this principle.
This figure shows several spheres. The front-middle sphere uses the Beere-Lambert Law to absorb certain frequencies of light. The front-right sphere has the same parameters as this sphere, except it does not implement the Beere-Lambert Law. This image took 5 hours and 24 minutes to render