Inject a render pass via scripting in URP

Unity raises a beginCameraRendering event before it renders each active CameraA component which creates an image of a particular viewpoint in your scene. The output is either drawn to the screen or captured as a texture. More info
See in Glossary in every frame. If a Camera is inactive (for example, if the Camera component checkbox is cleared on a Camera GameObject), Unity does not raise a beginCameraRendering event for this Camera.

When you subscribe a method to this event, you can execute custom logic before Unity renders the Camera. Examples of custom logic include rendering extra Cameras to Render TexturesA special type of Texture that is created and updated at runtime. To use them, first create a new Render Texture and designate one of your Cameras to render into it. Then you can use the Render Texture in a Material just like a regular Texture. More info
See in Glossary, and using those Textures for effects like planar reflections or surveillance camera views.

Other events in the RenderPipelineManager class provide more ways to customize URP. You can also use the principles described in this article with those events.

Use the RenderPipelineManager API

1. Subscribe a method to one of the events in the RenderPipelineManager class.

2. In the subscribed method, use the EnqueuePass method of a ScriptableRenderer instance to inject a custom render pass into the URP frame rendering.

For information about writing a render pass, refer to Write a render pass using the render graph system.

Example code:

public class EnqueuePass : MonoBehaviour
{
    [SerializeField] private BlurSettings settings;    
    private BlurRenderPass blurRenderPass;

    private void OnEnable()
    {
        ...
        blurRenderPass = new BlurRenderPass(settings);
        // Subscribe the OnBeginCamera method to the beginCameraRendering event.
        RenderPipelineManager.beginCameraRendering += OnBeginCamera;
    }

    private void OnDisable()
    {
        RenderPipelineManager.beginCameraRendering -= OnBeginCamera;
        blurRenderPass.Dispose();
        ...
    }

    private void OnBeginCamera(ScriptableRenderContext context, Camera cam)
    {
        ...
        // Use the EnqueuePass method to inject a custom render pass
        cam.GetUniversalAdditionalCameraData()
            .scriptableRenderer.EnqueuePass(blurRenderPass);
    }
}

Example

This example demonstrates how to subscribe a method to the beginCameraRendering event.

To follow the steps in this example, create a new Unity project using the Universal Project Template

1. In the sceneA Scene contains the environments and menus of your game. Think of each unique Scene file as a unique level. In each Scene, you place your environments, obstacles, and decorations, essentially designing and building your game in pieces. More info
   See in Glossary, create a Cube. Name it Example Cube.

2. In your Project, create a C# script. Call it URPCallbackExample.

3. Copy and paste the following code into the script. ```C# using UnityEngine; using UnityEngine.Rendering;

   public class URPCallbackExample : MonoBehaviour { // Unity calls this method automatically when it enables this component private void OnEnable() { // Add WriteLogMessage as a delegate of the RenderPipelineManager.beginCameraRendering event RenderPipelineManager.beginCameraRendering += WriteLogMessage; }

   // Unity calls this method automatically when it disables this component
   private void OnDisable()
   {
       // Remove WriteLogMessage as a delegate of the  RenderPipelineManager.beginCameraRendering event
       RenderPipelineManager.beginCameraRendering -= WriteLogMessage;
   }
   
   // When this method is a delegate of RenderPipeline.beginCameraRendering event, Unity calls this method every time it raises the beginCameraRendering event
   void WriteLogMessage(ScriptableRenderContext context, Camera camera)
   {
       // Write text to the console
       Debug.Log($"Beginning rendering the camera: {camera.name}");
   }
   

   } `` > **Note**: When you subscribe to an event, your handler method (in this example,WriteLogMessage) must accept the parameters defined in the event delegate. In this example, the event delegate isRenderPipeline.BeginCameraRendering, which expects the following parameters:<ScriptableRenderContext, Camera>`.

4. Attach the URPCallbackExample script to Example Cube.

5. Select Play. Unity prints the message from the script in the Console windowA Unity Editor window that shows errors, warnings and other messages generated by Unity, or your own scripts. More info
   See in Glossary each time Unity raises the beginCameraRendering event.

   

6. To raise a call to the OnDisable() method: In the Play mode, select Example Cube and clear the checkbox next to the script component title. Unity unsubscribes WriteLogMessage from the RenderPipelineManager.beginCameraRendering event and stops printing the message in the Console window.

   

Use a function in a MonoBehaviour

You can inject a Scriptable Render Pass into a scene via any GameObjectThe fundamental object in Unity scenes, which can represent characters, props, scenery, cameras, waypoints, and more. A GameObject’s functionality is defined by the Components attached to it. More info
See in Glossary present in the scene. This gives you more precise control over when the render pass is active. But this means you must have a GameObject inject the render pass at every point you want to use it. As a result, it’s better to inject any common effects in your project via a Scriptable Renderer Feature instead.

When you inject a Scriptable Render Pass into a scene via any GameObject, it’s important to consider how URP uses this script. The first Camera to render the Scriptable Render Pass uses up the render pass, and is the only Camera the render pass applies to. Any Cameras that the Scriptable Render Pass would apply that render after the first Camera don’t render the effect.

For example, if you have two Cameras and you add the Scriptable Render Pass in the Update method, only the first Camera to render uses the Scriptable Render Pass effect. This is because the first camera uses up the instance of the effect. As the second Camera renders before the next call of the Update method, a second instance of the Scriptable Render Pass isn’t available to use. As a result, the second Camera doesn’t apply the effect from the Scriptable Render Pass to its output.

Additional resources

Write a render pass using the render graph system