Unity 自定义Postprocess BloxBlur

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
        }
    }
}