how to fake global illumination:
1. for each point on a surface, ask yourself "if I was a tiny bug sitting on the surface of this object, what would the sky look like?"
2. think more about being a bug
3. enjoy thinking about being a bug
4. make a bugsona
5. make friends with other bugs
6. find a function that approximates the average sky colour. this will be a proxy for the hemispherical integral, and add that on top of any specular contribution