I'm using Blender 2.77 and I have currently arrived at the native Blender Renderer engine, and I fully want to understand how it works and how I can use, adapt, modify it for my own Blender projects.
I've already read many free e-books, articles and watched many videos about it, but I want to be able to truly understand AND visualize its inner workings.
Unfortunately the official Blender Render manual does not offer much in-depth/under-the-hood insight on how stuff really works.
QUESTION: - What ARE the World: Horizon, Zenith and Ambient colors? Are they real light sources (which gets internally ray-traced) or simply visual overlays which gets mixed onto the camera image?