Scriptable Render Pipeline introduction

This page explains how Unity’s Scriptable Render Pipeline (SRP) works, and introduces some key concepts and terminology. The information on this page is applicable to the Universal Render Pipeline (URP), the High Definition Render Pipeline (HDRP), and custom render pipelines that are based on SRP.

The Scriptable Render Pipeline is a thin API layer that lets you schedule and configure rendering commands using C# scripts. Unity passes these commands to its low-level graphics architecture, which then sends instructions to the graphics API.

URP and HDRP are built on top of SRP. You can also create your own custom render pipeline on top of SRP.

Render Pipeline Asset and Render Pipeline Instance

Every render pipeline based on SRP has two key customized elements:

• A Render Pipeline Asset, which is an asset in your Unity Project that stores configuration data about the render pipeline.
• A Render Pipeline Instance, which is a class that inherits from RenderPipeline. Its Render method is the main entry point to SRP.

For information about creating these elements in a custom render pipeline, see Creating a Render Pipeline Asset and a Render Pipeline Instance.

ScriptableRenderContext

ScriptableRenderContext is a class that acts as an interface between the custom C# code in the render pipeline and Unity’s low-level graphics code.

Use the ScriptableRenderContext API to schedule and execute rendering commands. For information, see Scheduling and executing rendering commands in the Scriptable Render Pipeline.

Entry points and callbacks

When working with SRP, use these to make Unity call your C# code at specific times.

• The Render method of the class that inherits from RenderPipeline is the main entry point to the SRP. If you are writing a custom render pipeline, this is where you should begin to write your code.
  
  Unity calls this method automatically. In a standalone application, Unity calls this method once per frame to render the main view, and once per frame for each manual call to ScriptRef:Camera.Render. In the Unity Editor, Unity calls this method once per frame for each Scene view or Game view that is visible, once per frame if if the Scene camera preview is visible, and once per frame for each manual call to ScriptRef:Camera.Render.
• The RenderPipelineManager class has the following events that you can subscribe to:
  • beginFrameRendering
  • beginCameraRendering
  • endCameraRendering
  • endFrameRendering