Unity’s Terrain system allows you to add vast landscapes to your game. At runtime, Terrain renderingThe process of drawing graphics to the screen (or to a render texture). By default, the main camera in Unity renders its view to the screen. More info
See in Glossary is highly optimized for efficiency. The Unity Editor provides a selection of tools to create Terrain quickly and easily. This section explains the various options available for Terrain, and how to make use of them.
2019–01–29 Page amended
Added information about the 2018.3 Terrain update and links to other resources