Creating a day/night cycle

Unifying the shading across many different world objects in our game gave us a very nice way of manipulating how the overall scene is actually represented. Many interesting effects are now possible, but we are going to focus on a rather simple yet effective one-lighting. The actual subtleties of the lighting subject will be covered in later chapters, but what we can do now is build a system that allows us to shade the world differently, based on the current time of the day, like so:

As you can tell, this effect can add a lot to a game and make it feel very dynamic. Let us take a look at how it can be implemented.

Updating the Map class

In order to accurately represent a day/night cycle, the game must keep a clock. Because it is relative to the world, the best place to keep track of this information is the Map class:

class Map : ... { 
  ... 
protected: 
  ... 
  float m_gameTime; 
  float m_dayLength; 
}; 

For the sake of having dynamic...