I found this neat exploration of the insides of Supreme Commander, the spiritual successor to one of my favorite games, Total Annihilation.
Specifically, in Supreme Commander – Graphics Study, Adrian Courrèges takes you through a tour of the rendering of a single frame of the game.
Animations show each step in the process, making it easy to see how you can go from culling a subset of the terrain to adding shadows to rendering meshes and particles to overlaying the UI.