前言

虽然Untiy 提供了不少postprocess功能，但这些功能是固定的，没法修改，这让我很不舒服。本文将介绍如果通过Render Feature来实现自定义PostProcess——Box Blur

测试环境

• Unity 2021.3.32
• Win 10
• JetBrains Rider 2023.2

Render Feature

• 什么是Render Feature

  • Render Feature类似于Pass，可以自定义渲染顺序、渲染对象、材质等
  • 说白了就是对于unity既定的渲染流程，可以在任意位置添加某个额外的功能(如描边)，也可以自定义数据

• 添加Render Feature

  先创建"Universal Render Pipeline Asset"(并导入"Graphics Setting")，在创建的同时会自动生成一个"Universal Render Pipeline Asset_Renderer"，在其中点击"Add Renderer Feature"，再点击"Render Objects"
  

  当然现在还未编写我们的Render Feature，因此找不到

Render Feature实现

• 创建Render Feature

  

• 创建后你将会看见两个class，一个是renderfeature，一个是renderpass。这里为什么pass是在renderfeature内呢，因为renderfeature负责将pass添加到Renderer 里面

  • 在renderfeature中，包含两个需要oveeride的函数，分别是Create()和AddRenderPasses()

    Create()：初始化renderfeature

    AddRenderPasses()：在 Renderer 中插入一个或多个 RenderPass

  • renderfeature实现

    public class BoxBlurPassFeature : ScriptableRendererFeature
    {
        // Inspector显示内容
        [System.Serializable]
        public class PassSetting
        {
            // 安插位置
            public RenderPassEvent m_passEvent = RenderPassEvent.AfterRenderingTransparents;
    
            // 控制分辨率
            [Range(1, 4)] 
            public int m_sampleWeaken = 1;
    
            // 模糊强度
            [Range(0, 20)] 
            public int m_blurIntensity = 5;
        }
    }
    

    在renderfeature中，我创建了一个setting class，用于管理renderpass和shader中的数据

    public PassSetting m_Setting = new PassSetting();
    BoxBlurRenderPass m_BoxBlurPass;
    
    /// <inheritdoc/>
    public override void Create()
    {
        m_BoxBlurPass = new BoxBlurRenderPass(m_Setting);
    }
    
    // Here you can inject one or multiple render passes in the renderer.
    // This method is called when setting up the renderer once per-camera.
    public override void AddRenderPasses(ScriptableRenderer renderer, ref RenderingData renderingData)
    {
        // can queue up multiple passes after each other
        renderer.EnqueuePass(m_BoxBlurPass);
    }
    

    在Create()中，添加renderpass的构造函数；在AddRenderPasses()添加具体的pass，可以是多个

RenderPass实现

• RenderPass才是灵魂，它的实现如下

  class BoxBlurRenderPass : ScriptableRenderPass
  {
      // profiler tag will show up in frame debugger
      private const string m_ProfilerTag = "Box Blur Pass";
  
      // 用于存储pass setting
      private BoxBlurPassFeature.PassSetting m_passSetting;
  
      // 目标图像和临时图像
      private RenderTargetIdentifier m_TargetBuffer, m_TempBuffer;
      private int m_TempBufferID = Shader.PropertyToID("_TemporaryBuffer");
  
      private Material m_Material;
  
      // 来自shader
      // int 相较于 string可以获得更好的性能，因为这是预处理的
      private static readonly int m_BlurIntensityProperty = Shader.PropertyToID("_BlurIntensity");
  }
  

  先定义一系列RenderPass需要的数据

  // 用于设置material 属性
  public BoxBlurRenderPass(BoxBlurPassFeature.PassSetting passSetting)
  {
      this.m_passSetting = passSetting;
  
      // 定义安插位置
      renderPassEvent = m_passSetting.m_passEvent;
  
      // 使用的shader
      if (m_Material == null) m_Material = CoreUtils.CreateEngineMaterial("Custom/PP_BoxBlur");
  
      // 基于pass setting设置material Properties
      m_Material.SetInt(m_BlurIntensityProperty, m_passSetting.m_blurIntensity);
  }
  

  // Gets called by the renderer before executing the pass.
  // Can be used to configure render targets and their clearing state.
  // Can be used to create temporary render target textures.
  // If this method is not overriden, the render pass will render to the active camera render target.
  public override void OnCameraSetup(CommandBuffer cmd, ref RenderingData renderingData)
  {
      // camera target descriptor will be used when creating a temporary render texture
      RenderTextureDescriptor descriptor = renderingData.cameraData.cameraTargetDescriptor;
  
      // Downsample original camera target descriptor
      descriptor.width /= m_passSetting.m_sampleWeaken;
      descriptor.height /= m_passSetting.m_sampleWeaken;
  
      // Set the number of depth bits we need for temporary render texture
      descriptor.depthBufferBits = 0;
  
      // Enable these if pass requires access to the CameraDepthTexture or the CameraNormalsTexture.
      // ConfigureInput(ScriptableRenderPassInput.Depth);
      // ConfigureInput(ScriptableRenderPassInput.Normal);
  
      // Grab the color buffer from the renderer camera color target
      m_TargetBuffer = renderingData.cameraData.renderer.cameraColorTarget;
  
      // Create a temporary render texture using the descriptor from above
      cmd.GetTemporaryRT(m_TempBufferID, descriptor, FilterMode.Bilinear);
      m_TempBuffer = new RenderTargetIdentifier(m_TempBufferID);
  
  }
  

  在该函数中，主要用于控制camera render target图像的分辨率，depth buffer的精度，及获取camera render target和创建临时的渲染纹理

  // The actual execution of the pass. This is where custom rendering occurs
  public override void Execute(ScriptableRenderContext context, ref RenderingData renderingData)
  {
      // Grab a command buffer. We put the actual execution of the pass inside of a profiling scope
      CommandBuffer cmd = CommandBufferPool.Get();
  
      using (new ProfilingScope(cmd, new ProfilingSampler(m_ProfilerTag)))
      {
          // Blit from the color buffer to a temporary buffer and back. This is needed for a two-pass shader
          Blit(cmd, m_TargetBuffer, m_TempBuffer, m_Material, 0);
          Blit(cmd, m_TempBuffer, m_TargetBuffer, m_Material, 1);
      }
      
      // Execute the command buffer and release it
      context.ExecuteCommandBuffer(cmd);
      CommandBufferPool.Release(cmd);
  }
  

  Execute()定义了pass的执行规则，我们正是在该函数中实现后处理的。将需要执行的pass放置于profiling scope，Blit()用于将源纹理计算后复制到目标渲染纹理，最后执行并释放命令缓冲区

  // Called when the camera has finished rendering
  // release/cleanup any allocated resources that were created by this pass
  public override void OnCameraCleanup(CommandBuffer cmd)
  {
      if(cmd == null) throw new ArgumentNullException("cmd");
      
      // Since created a temporary render texture in OnCameraSetup, we need to release the memory here to avoid a leak
      cmd.ReleaseTemporaryRT(m_TempBufferID);
  }
  

  执行完pass后，释放render target占用的内存

  全部实现如下

  using System;
  using UnityEngine;
  using UnityEngine.Rendering;
  using UnityEngine.Rendering.Universal;
  
  public class BoxBlurPassFeature : ScriptableRendererFeature
  {
      // render feature 显示内容
      [System.Serializable]
      public class PassSetting
      {
          // 安插位置
          public RenderPassEvent m_passEvent = RenderPassEvent.AfterRenderingTransparents;
  
          // 控制分辨率
          [Range(1, 4)] 
          public int m_sampleWeaken = 1;
  
          // 模糊强度
          [Range(0, 20)] 
          public int m_blurIntensity = 5;
          
      }
      
      class BoxBlurRenderPass : ScriptableRenderPass
      {
          // profiler tag will show up in frame debugger
          private const string m_ProfilerTag = "Box Blur Pass";
  
          // 用于存储pass setting
          private BoxBlurPassFeature.PassSetting m_passSetting;
  
          private RenderTargetIdentifier m_TargetBuffer, m_TempBuffer;
          private int m_TempBufferID = Shader.PropertyToID("_TemporaryBuffer");
  
          private Material m_Material;
  
          // int 相较于 string可以获得更好的性能，因为这是预处理的
          private static readonly int m_BlurIntensityProperty = Shader.PropertyToID("_BlurIntensity");
  
          // 用于设置material 属性
          public BoxBlurRenderPass(BoxBlurPassFeature.PassSetting passSetting)
          {
              this.m_passSetting = passSetting;
  
              renderPassEvent = m_passSetting.m_passEvent;
  
              if (m_Material == null) m_Material = CoreUtils.CreateEngineMaterial("Custom/PP_BoxBlur");
              
              // 基于pass setting设置material Properties
              m_Material.SetInt(m_BlurIntensityProperty, m_passSetting.m_blurIntensity);
          }
          
          // Gets called by the renderer before executing the pass.
          // Can be used to configure render targets and their clearing state.
          // Can be used to create temporary render target textures.
          // If this method is not overriden, the render pass will render to the active camera render target.
          public override void OnCameraSetup(CommandBuffer cmd, ref RenderingData renderingData)
          {
              // camera target descriptor will be used when creating a temporary render texture
              RenderTextureDescriptor descriptor = renderingData.cameraData.cameraTargetDescriptor;
  
              // Downsample original camera target descriptor
              descriptor.width /= m_passSetting.m_sampleWeaken;
              descriptor.height /= m_passSetting.m_sampleWeaken;
              
              // Set the number of depth bits we need for temporary render texture
              descriptor.depthBufferBits = 0;
              
              // Enable these if pass requires access to the CameraDepthTexture or the CameraNormalsTexture.
              // ConfigureInput(ScriptableRenderPassInput.Depth);
              // ConfigureInput(ScriptableRenderPassInput.Normal);
              
              // Grab the color buffer from the renderer camera color target
              m_TargetBuffer = renderingData.cameraData.renderer.cameraColorTarget;
              
              // Create a temporary render texture using the descriptor from above
              cmd.GetTemporaryRT(m_TempBufferID, descriptor, FilterMode.Bilinear);
              m_TempBuffer = new RenderTargetIdentifier(m_TempBufferID);
  
          }
  
          // The actual execution of the pass. This is where custom rendering occurs
          public override void Execute(ScriptableRenderContext context, ref RenderingData renderingData)
          {
              // Grab a command buffer. We put the actual execution of the pass inside of a profiling scope
              CommandBuffer cmd = CommandBufferPool.Get();
  
              using (new ProfilingScope(cmd, new ProfilingSampler(m_ProfilerTag)))
              {
                  // Blit from the color buffer to a temporary buffer and back. This is needed for a two-pass shader
                  Blit(cmd, m_TargetBuffer, m_TempBuffer, m_Material, 0);
                  Blit(cmd, m_TempBuffer, m_TargetBuffer, m_Material, 1);
              }
              
              // Execute the command buffer and release it
              context.ExecuteCommandBuffer(cmd);
              CommandBufferPool.Release(cmd);
          }
          
          // Called when the camera has finished rendering
          // release/cleanup any allocated resources that were created by this pass
          public override void OnCameraCleanup(CommandBuffer cmd)
          {
              if(cmd == null) throw new ArgumentNullException("cmd");
              
              // Since created a temporary render texture in OnCameraSetup, we need to release the memory here to avoid a leak
              cmd.ReleaseTemporaryRT(m_TempBufferID);
          }
      }
  
      public PassSetting m_Setting = new PassSetting();
      BoxBlurRenderPass m_BoxBlurPass;
      
      /// <inheritdoc/>
      public override void Create()
      {
          m_BoxBlurPass = new BoxBlurRenderPass(m_Setting);
      }
  
      // Here you can inject one or multiple render passes in the renderer.
      // This method is called when setting up the renderer once per-camera.
      public override void AddRenderPasses(ScriptableRenderer renderer, ref RenderingData renderingData)
      {
          // can queue up multiple passes after each other
          renderer.EnqueuePass(m_BoxBlurPass);
      }
  }
  
  
  
  

Shader

• shader部分就很简单

  {
      Properties
      {
          // 注意该属性名称是固定的
          _MainTex("Main Tex", 2D) = "white"{}
          _BlurIntensity("Box Blur Intensity", Int) = 1
      }
      
      SubShader
      {
          Tags
          {
              "RenderType" = "Opaque"
              "RenderPipeline" = "UniversalPipeline"
          }
          
          HLSLINCLUDE
          #pragma vertex VS
          #pragma fragment PS
          
          #include "Packages/com.unity.render-pipelines.universal/ShaderLibrary/Core.hlsl"
          CBUFFER_START(UnityPerMaterial)
          float4 _MainTex_ST;
          float4 _MainTex_TexelSize;
          int _BlurIntensity;
          CBUFFER_END
          TEXTURE2D(_MainTex);
          SAMPLER(sampler_MainTex);
  
          struct VSInput
          {
              float4 positionL : POSITION;
              float2 uv : TEXCOORD0;
          };
          
          struct PSInput
          {
              float4 positionH : SV_POSITION;
              float2 uv : TEXCOORD0;
          };
  
          PSInput VS(VSInput vsInput)
          {
              PSInput vsOutput;
  
              vsOutput.positionH = TransformObjectToHClip(vsInput.positionL);
              vsOutput.uv = TRANSFORM_TEX(vsInput.uv, _MainTex);
  
              return vsOutput;
          }
          
          ENDHLSL
  
          Pass
          {
              Name "VERTICAL BOX BLUR"
              
              HLSLPROGRAM
  
              float4 PS(PSInput psInput) : SV_TARGET
              {
                  float2 texelSize = _MainTex_TexelSize.xy;
                  float4 sum = 0;
  
                  int sampleRange = 2 * _BlurIntensity + 1;
  
                  for(float y = 0; y < sampleRange; ++y)
                  {
                      float2 offset = float2(0, y - _BlurIntensity);
                      sum += SAMPLE_TEXTURE2D(_MainTex, sampler_MainTex, psInput.uv + offset * texelSize);
                  }
  
                  return sum / sampleRange;
              }
              
              ENDHLSL
          }
  
          Pass
          {
              Name "HORIZONTAL BOX BLUR"
              
              HLSLPROGRAM
  
              float4 PS(PSInput psInput) : SV_TARGET
              {
                  float2 texelSize = _MainTex_TexelSize.xy;
                  float4 sum = 0;
  
                  int sampleRange = 2 * _BlurIntensity + 1;
  
                  for(float x = 0; x < sampleRange; ++x)
                  {
                      float2 offset = float2(x - _BlurIntensity, 0);
                      sum += SAMPLE_TEXTURE2D(_MainTex, sampler_MainTex, psInput.uv + offset * texelSize);
                  }
  
                  return sum / sampleRange;
              }
              
              ENDHLSL
          }
      }
  }
  

效果

reference

https://docs.unity.cn/cn/2020.3/Manual/script-Serialization.html

https://blog.csdn.net/qq_15020543/article/details/82761416

https://zhuanlan.zhihu.com/p/348500968

https://zhuanlan.zhihu.com/p/396965255

https://zhuanlan.zhihu.com/p/373273390

https://docs.unity3d.com/Packages/com.unity.render-pipelines.universal@13.1/manual/upgrade-guide-2022-1.html

https://ameye.dev/notes/scriptable-render-passes/