Unity 自定义Postprocess

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_HSCPass;	// 自定义的renderpass
      
      public override void Create()
      {
          // renderpass构造函数
          m_HSCPass = 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_HSCPass);
      }
      

      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 = "HSC 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

Shader

  • shader部分就很简单

    {
        Properties
        {
            _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/

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