By default we create a single
World when entering Play Mode and populate it with all available
ComponentSystem objects in the project, but you can disable the default
World creation and replace it with your own code via a global define.
- Default World creation code (see file: Packages/com.unity.entities/Unity.Entities.Hybrid/Injection/DefaultWorldInitialization.cs)
- Automatic bootstrap entry point (see file: Packages/com.unity.entities/Unity.Entities.Hybrid/Injection/AutomaticWorldBootstrap.cs)