搭建URP场景

Render Feature作用是支持SRP扩展自定义渲染pass，因此需要在SRP下使用，这里选择URP，在package manager中找到Universal RP并install。

?创建一个前向渲染管线资产，会生成一个UniversalRenderPipelineAsset和UniversalRenderPipelineAsset_Renderer文件。

?在Edit-Project Settings-Graphics中将渲染管线设置为刚设置好的URP Asset

场景就自由发挥搭建吧

Render Feature脚本

MyBlitFeature.cs

using UnityEngine;
using UnityEngine.Rendering.Universal;

public class MyBlitFeature : ScriptableRendererFeature
{
    [System.Serializable]
    public class MyFeatureSettings
    {
        // 在inspector面板中设置开关，插入pass的位置，材质
        public bool IsEnabled = true;
        public RenderPassEvent WhenToInsert = RenderPassEvent.AfterRendering;
        public Material MaterialToBlit;
    }

    // 命名为"settings" (小写) 才能在inspector面板中正确显示
    public MyFeatureSettings settings = new MyFeatureSettings();

    RenderTargetHandle renderTextureHandle;
    MyBlitRenderPass myRenderPass;

    // 创建pass，参数为pass名称、pass插入位置、渲染用到的材质
    public override void Create()
    {
        myRenderPass = new MyBlitRenderPass(
          "My custom pass",
          settings.WhenToInsert,
          settings.MaterialToBlit
        );
    }

    // 每帧调用一次这个方法将自定义pass加入渲染管线中
    public override void AddRenderPasses(ScriptableRenderer renderer, ref RenderingData renderingData)
    {
        if (!settings.IsEnabled)
        {
            // 关闭则不添加
            return;
        }

        // 获取一些渲染所需信息，此处是摄像机的color buffer
        var cameraColorTargetIdent = renderer.cameraColorTarget;
        myRenderPass.Setup(cameraColorTargetIdent);

        // 添加pass.
        // Could queue up multiple passes and/or pick passes to use
        renderer.EnqueuePass(myRenderPass);
    }
}

?MyBlitRenderPass.cs

using UnityEngine;
using UnityEngine.Rendering;
using UnityEngine.Rendering.Universal;

class MyBlitRenderPass : ScriptableRenderPass
{
    // 用来在Frame Debug工具中标识pass名
    string profilerTag;

    Material materialToBlit;
    RenderTargetIdentifier cameraColorTargetIdent;
    RenderTargetHandle tempTexture;

    public MyBlitRenderPass(string profilerTag,
      RenderPassEvent renderPassEvent, Material materialToBlit)
    {
        this.profilerTag = profilerTag;
        this.renderPassEvent = renderPassEvent;
        this.materialToBlit = materialToBlit;
    }

    // 用来被Feature类调用初始化一些需要的数据，例如本例中的相机Color buffer
    public void Setup(RenderTargetIdentifier cameraColorTargetIdent)
    {
        this.cameraColorTargetIdent = cameraColorTargetIdent;
    }

    // 该方法每帧Execute方法执行前被调用, 用作渲染前准备工作
    public override void Configure(CommandBuffer cmd, RenderTextureDescriptor cameraTextureDescriptor)
    {
        // 使用相机渲染目标参数创建临时纹理
        cmd.GetTemporaryRT(tempTexture.id, cameraTextureDescriptor);
    }

    // 每帧每个符合条件的相机会执行一次，渲染发生时不会再调用。所以只能通过cmd执行渲染，不能在这里写渲染命令。
    // RenderingData（没有清晰的文档）提供了一系列场景还有被渲染的信息 provides a bunch of (not very well documented)
    public override void Execute(ScriptableRenderContext context, ref RenderingData renderingData)
    {
        // 获取cmd
        CommandBuffer cmd = CommandBufferPool.Get(profilerTag);
        cmd.Clear();

        // 实际渲染pass
        // 将相机纹理通过材质生成到临时纹理中
        cmd.Blit(cameraColorTargetIdent, tempTexture.Identifier(), materialToBlit, 0);

        // 再将临时纹理内容复制回相机颜色缓冲中
        cmd.Blit(tempTexture.Identifier(), cameraColorTargetIdent);

        // 执行cmd
        context.ExecuteCommandBuffer(cmd);

        // 释放cmd
        cmd.Clear();
        CommandBufferPool.Release(cmd);
    }

    // Excute方法后执行，在这里释放Configure中分配的内存
    public override void FrameCleanup(CommandBuffer cmd)
    {
        cmd.ReleaseTemporaryRT(tempTexture.id);
    }
}

创建材质

原文用Shader Graph创建的一个Invert shader我不知道为什么不行，有试过的朋友如果有同样问题最后解决了可以告诉我下为啥？

我换了个其他后处理shader，创建一个Material，使用这个shader

Shader "Custom/BrightnessSaturationAndContrast"
{
    Properties
    {
        _MainTex ("Texture", 2D) = "white" {}
        _Brightness("Brightness", Float) = 1
        _Saturation("Saturation", Float) = 1
        _Contrast("_Contrast", Float) = 1
    }
    SubShader
    {
        // No culling or depth
        Cull Off ZWrite Off ZTest Always

        Pass
        {
            CGPROGRAM
            #pragma vertex vert
            #pragma fragment frag

            #include "UnityCG.cginc"

            sampler2D _MainTex;
            half _Brightness;
            half _Saturation;
            half _Contrast;

            struct v2f
            {
                float2 uv : TEXCOORD0;
                float4 pos : SV_POSITION;
            };

            v2f vert (appdata_img v)
            {
                v2f o;
                o.pos = UnityObjectToClipPos(v.vertex);
                o.uv = v.texcoord;
                return o;
            }

            fixed4 frag (v2f i) : SV_Target
            {
                fixed4 renderTex = tex2D(_MainTex, i.uv);
                fixed3 finalColor = renderTex.rgb * _Brightness;

                fixed luminance = 0.2125 * renderTex.r + 0.7154 * renderTex.g + 0.0721 * renderTex.b;
                fixed3 luminanceColor = fixed3(luminance, luminance, luminance);
                finalColor = lerp(luminanceColor, finalColor, _Saturation);

                fixed avgColor = fixed3(0.5,0.5, 0.5);
                finalColor = lerp(avgColor, finalColor, _Contrast);

                return fixed4(finalColor, renderTex.a);
            }
            ENDCG
        }
    }
}