On top of the low-level native plugin interface, Unity also supports low level rendering extensions that can receive callbacks when certain events happen. This is mostly used to implement and control low-level rendering in your plugin and enable it to work with Unity’s multithreaded rendering.
Due to the low-level nature of this extension the plugin might need to be preloaded before the devices get created. Currently the convention is name-based; the plugin name must begin GfxPlugin (for example: GfxPluginMyNativePlugin).
The rendering extension definition exposed by Unity is in the file IUnityRenderingExtensions.h, provided with the Editor (see file path Unity\Editor\Data\PluginAPI).
All platforms supporting native plugins support these extensions.
To take advantage of the rendering extension, a plugin should export UnityRenderingExtEvent and optionally UnityRenderingExtQuery. There is a lot of documentation provided inside the include file.
A plugin gets called via UnityRenderingExtEvent whenever Unity triggers one of the built-in events. The callbacks can also be added to CommandBuffers via CommandBuffer.IssuePluginEventAndData or CommandBuffer.IssuePluginCustomBlit from scripts.