Unity Game Optimization - Third Edition

Global Illumination

Global Illumination (GI) is an implementation of baked lightmapping. Lightmapping is similar to the shadow maps created by shadowing techniques in that one or more textures are generated for each object that represents extra lighting information and is later applied to the object during its lighting pass of a fragment shader to simulate static lighting effects.

The main difference between these lightmaps and other forms of lighting is that lightmaps are pre-generated (or baked) in the Editor and packaged into the game build. This ensures that we don't need to keep regenerating this information at runtime, saving numerous draw calls and significant GPU activity. Since we can bake this data, we have the luxury of time to ...