URP中修改相机RenderTarget

原来在BuildIn中修改RenderTarget很容易，它可以让我们用额外的相机照画面进行后处理再贴到指定的对象上，比如镜子，湖面，但是最近项目用了URP后渲染管线变了，问了同事后才知道需要单独接管额外相机的渲染，整理后代码如下:

using System.Collections;
using System.Collections.Generic;
using UnityEngine;
using UnityEngine.Rendering;
using UnityEngine.Rendering.Universal;

public class JCTest : MonoBehaviour
{
    public Camera mCamera;
    public RenderTexture mRT;

    void OnEnable()
    {
        RenderPipelineManager.beginCameraRendering += OnBeginCameraRendering;
        mRT = RenderTexture.GetTemporary(512, 512, 16, RenderTextureFormat.ARGB32);
        mCamera.targetTexture = mRT;
    }


    void OnDisable()
    {
        RenderPipelineManager.beginCameraRendering -= OnBeginCameraRendering;
        RenderTexture.ReleaseTemporary(mRT);
    }


    private void OnBeginCameraRendering(ScriptableRenderContext context, Camera camera)
    {
        if (camera.cameraType == CameraType.SceneView || camera.cameraType == CameraType.Preview)
            return;
        UniversalRenderPipeline.RenderSingleCamera(context, mCamera);
    }

}

注意事项:

1.按管的相机不需要添加到base相机的stack中

2，接管的相机需要在RenderPipelineManger.beginCameraRendering时调用，RenderSingleCamera方法，且必须为base相机，因为UniversalRenderPipeline.RenderSingleCamera方法中过滤了overlay相机，源码如下:

        public static void RenderSingleCamera(ScriptableRenderContext context, Camera camera)
        {
            UniversalAdditionalCameraData additionalCameraData = null;
            if (IsGameCamera(camera))
                camera.gameObject.TryGetComponent(out additionalCameraData);

            if (additionalCameraData != null && additionalCameraData.renderType != CameraRenderType.Base)
            {
                Debug.LogWarning(
                    "Only Base cameras can be rendered with standalone RenderSingleCamera. Camera will be skipped.");
                return;
            }

            InitializeCameraData(camera, additionalCameraData, out var cameraData);
            RenderSingleCamera(context, cameraData, true, cameraData.postProcessEnabled);
        }

运行结果如下: