Modern game lighting makes extensive use of ‘global illumination’. Global illumination, or ‘GI’, is a term used to describe a range of techniques and mathematical models which attempt to simulate the complex behaviour of light as it bounces and interacts with the world. Simulating global illumination accurately is challenging and can be computationally expensive. Because of this, games use a range of approaches to handle these calculations beforehand, rather than during gameplay. In this tutorial we will give you an overview of how GI works in Unity. We will walk you through the different lighting techniques available, explain how to setup your project for lighting and then explore the various tools at your disposal when considering how to light a scene.