【URP】Unity 插入自定义RenderPass

自定义渲染通道是一种改变通用渲染管道（URP）如何渲染场景或场景中的对象的方法。自定义呈现通道(RenderPass)包含自己的Render代码，可以在注入点将其添加到RenderPass中。

【从UnityURP开始探索游戏渲染】专栏-直达

添加自定义呈现通道(RenderPass)：

• 使用Scriptable render pass API创建自定义render pass的代码。
• 将自定的render pass注入到URP管线中的指定注入点中，有两种方式：
  • 用RenderPipelineManager API注入自定义渲染通道
  • 或者通过创建一个可脚本化的RendererFeature添加到URP渲染器中。

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使用Scriptable render pass API创建自定义render pass

• Example custom render pass

  using UnityEngine;
  using UnityEngine.Rendering;
  using UnityEngine.Rendering.Universal;
  
  internal class ColorBlitPass : ScriptableRenderPass
  {
      ProfilingSampler m_ProfilingSampler = new ProfilingSampler("ColorBlit");
      Material m_Material;
      RTHandle m_CameraColorTarget;
      float m_Intensity;
  
      public ColorBlitPass(Material material)
      {
          m_Material = material;
          renderPassEvent = RenderPassEvent.BeforeRenderingPostProcessing;
      }
  
      public void SetTarget(RTHandle colorHandle, float intensity)
      {
          m_CameraColorTarget = colorHandle;
          m_Intensity = intensity;
      }
  
      public override void OnCameraSetup(CommandBuffer cmd, ref RenderingData renderingData)
      {
          ConfigureTarget(m_CameraColorTarget);
      }
  
      public override void Execute(ScriptableRenderContext context, ref RenderingData renderingData)
      {
          var cameraData = renderingData.cameraData;
          if (cameraData.camera.cameraType != CameraType.Game)
              return;
  
          if (m_Material == null)
              return;
  
          CommandBuffer cmd = CommandBufferPool.Get();
          using (new ProfilingScope(cmd, m_ProfilingSampler))
          {
              m_Material.SetFloat("_Intensity", m_Intensity);
              Blitter.BlitCameraTexture(cmd, m_CameraColorTarget, m_CameraColorTarget, m_Material, 0);
          }
          context.ExecuteCommandBuffer(cmd);
          cmd.Clear();
  
          CommandBufferPool.Release(cmd);
      }
  }

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将自定的render pass注入到URP管线中的指定注入点中

用RenderPipelineManager API注入自定义渲染通道

• 通过RenderPipelineManager的注入点委托提供执行时机，加上Camera的EnqueuePass方法注入自定义RenderPass。

  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);
      }
  }

创建一个可脚本化的RendererFeature

此示例执行将屏幕染成绿色的全屏blit。

• 要创建自定义渲染通道，创建一个名为ColorBlitPass.cs的新c#脚本，然后从示例自定义渲染通道部分粘贴代码。

  • 注意：这个例子使用了Blitter API。不要使用CommandBuffer。URP中的Blit API。更多信息请参考Blit。
  • 使用上面定义好的定制Render Pass

• 要创建Scriptable RendererFeature，将自定义渲染通道添加到渲染循环中，请创建一个名为ColorBlitRendererFeature.cs的新c#脚本，然后将示例Scriptable RendererFeature部分中的代码粘贴进来。

  • Example Scriptable Renderer Feature Scriptable Renderer Feature 添加 render pass 到渲染循环.

    using UnityEngine;
    using UnityEngine.Rendering;
    using UnityEngine.Rendering.Universal;
    
    internal class ColorBlitRendererFeature : ScriptableRendererFeature
    {
        public Shader m_Shader;
        public float m_Intensity;
    
        Material m_Material;
    
        ColorBlitPass m_RenderPass = null;
    
        public override void AddRenderPasses(ScriptableRenderer renderer,
                                        ref RenderingData renderingData)
        {
            if (renderingData.cameraData.cameraType == CameraType.Game)
                renderer.EnqueuePass(m_RenderPass);
        }
    
        public override void SetupRenderPasses(ScriptableRenderer renderer,
                                            in RenderingData renderingData)
        {
            if (renderingData.cameraData.cameraType == CameraType.Game)
            {
                // Calling ConfigureInput with the ScriptableRenderPassInput.Color argument
                // ensures that the opaque texture is available to the Render Pass.
                m_RenderPass.ConfigureInput(ScriptableRenderPassInput.Color);
                m_RenderPass.SetTarget(renderer.cameraColorTargetHandle, m_Intensity);
            }
        }
    
        public override void Create()
        {
            m_Material = CoreUtils.CreateEngineMaterial(m_Shader);
            m_RenderPass = new ColorBlitPass(m_Material);
        }
    
        protected override void Dispose(bool disposing)
        {
            CoreUtils.Destroy(m_Material);
        }
    }

• 要创建将像素染成绿色的着色器代码，请创建一个着色器文件，然后从示例着色器部分粘贴代码。

• Example shader

  • 着色器执行渲染的GPU端。它从相机中采样颜色纹理，然后输出绿色值设置为所选强度的颜色。 注意：与Blitter API一起使用的着色器必须是手工编码的着色器。图形着色器与Blitter API不兼容。

    Shader "ColorBlit"
    {
        SubShader
        {
            Tags { "RenderType"="Opaque" "RenderPipeline" = "UniversalPipeline"}
            LOD 100
            ZWrite Off Cull Off
            Pass
            {
                Name "ColorBlitPass"
    
                HLSLPROGRAM
                #include "Packages/com.unity.render-pipelines.universal/ShaderLibrary/Core.hlsl"
                
                // The Blit.hlsl file provides the vertex shader (Vert),
                // the input structure (Attributes) and the output structure (Varyings)
                #include "Packages/com.unity.render-pipelines.core/Runtime/Utilities/Blit.hlsl"
    
                #pragma vertex Vert
                #pragma fragment frag
    
                // Set the color texture from the camera as the input texture
                TEXTURE2D_X(_CameraOpaqueTexture);
                SAMPLER(sampler_CameraOpaqueTexture);
    
                // Set up an intensity parameter
                float _Intensity;
    
                half4 frag (Varyings input) : SV_Target
                {
                    UNITY_SETUP_STEREO_EYE_INDEX_POST_VERTEX(input);
    
                    // Sample the color from the input texture
                    float4 color = SAMPLE_TEXTURE2D_X(_CameraOpaqueTexture, sampler_CameraOpaqueTexture, input.texcoord);
    
                    // Output the color from the texture, with the green value set to the chosen intensity
                    return color * float4(0, _Intensity, 0, 1);
                }
                ENDHLSL
            }
        }
    }

• 将ColorBlitRendererFeature添加到当前URP Renderer资源中。有关更多信息，请参阅向URP渲染器添加渲染器功能。

• 要更改亮度，请调整Color Blit Renderer Feature组件中的Intensity属性。

注意：如果项目使用XR，为了使示例可视化，在项目中安装MockHMD XR插件包，然后将渲染模式属性设置为单通道实例化。

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docs.unity3d.com/Packages/co...

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【从UnityURP开始探索游戏渲染】专栏-直达

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