Version: 2020.3
Vertex Lit Rendering Path
Hardware requirements for the Built-in Render Pipeline
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Extending the Built-in Render Pipeline with CommandBuffers

This page contains information on using CommandBuffers in the Built-in Render Pipeline. For information on using CommandBuffers in render pipelines based on the Scriptable 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
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Pipeline, see Scheduling and executing rendering commands in the Scriptable Rendering Pipeline.

CommandBuffer fundamentals

A CommandBuffer holds a list of rendering commands (such as setting the render target, or drawing a given mesh). You can instruct Unity to schedule and execute those commands at various points in the Built-in Render Pipeline, which allows you to customize and extend Unity’s rendering functionality.

Blurry refraction, using Command Buffers.
Blurry refraction, using Command Buffers.

You can execute CommandBuffers immediately using the Graphics.ExecuteCommandBuffer API, or you can schedule them so that they occur at a given point in the render pipeline. To schedule them, use the Camera.AddCommandBuffer API with the CameraEvent enum, and the Light.AddCommandBuffer API with the LightEvent enum. To see when Unity executes CommandBuffers that you schedule in this way, see CameraEvent and LightEvent order of execution.

For a full list of the commands that you can execute using CommandBuffers, see the CommandBuffer API documentation. Note that some commands are supported only on certain hardware; for example, the commands relating to ray tracingThe process of generating an image by tracing out rays from the Camera through each pixel and recording the color contribution at the hit point. This is an alternative to rasterization. raytracing
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are supported only in DX12.

Command Buffer examples

Decals, using Command Buffers.
Decals, using Command Buffers.

The Unity blog post Extending Unity 5 rendering pipeline: Command Buffers introduces CommandBuffers in the Built-in Render Pipeline. It describes how to use CommandBuffers to achieve several different effects, and contains a sample project and example code. The project was created for an older version of Unity, but the principles are the same.

CameraEvent and LightEvent event order of execution

CameraEvent

The order of execution for CameraEvents depends on the rendering pathThe technique Unity uses to render graphics. Choosing a different path affects the performance of your game, and how lighting and shading are calculated. Some paths are more suited to different platforms and hardware than others. More info
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that your Project uses.

Deferred rendering path

Forward rendering path

LightEvent order of execution

During the “render shadows” stage above, for each shadow-casting Light, Unity performs these steps:

Vertex Lit Rendering Path
Hardware requirements for the Built-in Render Pipeline