public sealed enum Sandbox.GameObjectSystem.Stage : System.Enum

Command Lists are deferred commands to execute on the renderer on certain rendering stage, this replaces the previous RenderHook system

To make a post process shader you should derive from BasePostProcess<T>. This makes it easier to make a component that will be able to blend from multiple others.

The FilmGrain component adds simulated film-style grain to the camera output. It's purely visual – it does not affect gameplay or lighting – and is intended to add texture, grit or stylistic noise to the final image.

A scene can contain systems that need to do work in specific places during the frame.