This assignment implements a more elegant diffuse lighting model for surfaces and add area lights/soft shadows. The Cornell Box is used to demonstrate these techniques.

The amount of light on a surface at location x' from a lightsource at location x is calculated by the following equation:
L(x')=s(x,x')*R(x')/pi*(cos theta*cos theta')/(||x-x'||^2)*A
where:
s(x,x'): is a function returning 1 or 0, determining the visibility of point x from x'
R(x'): is the reflectance value of the surface at x'
theta: is the angle between the surface normal at x and the ray between x and x'
theta': is the angle between the surface normal at x' and the ray between x' and x
A: is the surface area of the light
x: is a stratified random sample on the surface of the light.

Using a stratified sampling strategy to find a random point on the area light causes the image to converge much faster to a 'noiseless' rendering. Originally, I was using a simple uniform random sampling, and the image sampled at 25 rays/pixel looked about the same as 4 rays/pixel does now!