This is part of a series about a critical theoretical approach to understanding video game lighting, while staying grounded in technical realities, and not focusing on a specific game engine.
Last time
(part 4), we ended with the idea that video game lighting is a carefully assembled pile of hacks / effects that hopefully seems like a unified phenomenon of light. It might seem annoying to fuss over many details all the time, but this bespoke workflow exists because we need so much control to make sure the lighting calculations doesn't slow our game's framerate.
One of the most "expensive" (computer-intensive) parts of 3D video games is rendering shadows. To calculate a shadow in a video game, we must test-fire many light rays out from the light source. If these rays hit anything
(see diagram above) then that means the light casts shadows past that object. To give you an idea of how much we sacrifice to shadows,
Crytek said in a 2013 SIGGRAPH talk that they offer ~20% of their frame budget (5-7 FPS out of 30 FPS) to the shadows. (20% of their entire game! just for shadows!)
Since shadows are so expensive to do, it's impressive when we manage to do it anyway. But that also means we want shadows to pull their weight and help sell the game, to justify the work we put into them. We worship shadows while praying for something in return.
The cult of hard shadows began on February 21, 2001, at the Macworld conference in Tokyo: