unityURP6+版本中后处理如何实现抓屏(语言-c#)

Question

网上关于这个6+版本URP后处理教程太少了QWQ，我在学习这个时在测试脚本中进行抓屏，要么屏幕全黑，要么一堆报错，网上也没找到解决办法，可能是我的抓拍方式有问题，附上后处理脚本代码

using System;
using UnityEngine;
using UnityEngine.Rendering;
using UnityEngine.Rendering.RenderGraphModule;
using UnityEngine.Rendering.Universal;

public class SSPRFeature : ScriptableRendererFeature
{
    public Texture2D renderTexture1;
    public RenderTexture renderTexture2;
    public RenderTexture renderTexture3;
    public Material material;
    public SSPRPass SSPRpass;
    public string passName;
    public RenderPassEvent renderPassEvent;
    public override void Create()
    {
        SSPRpass = new SSPRPass(material, renderPassEvent, passName, renderTexture1, renderTexture2, renderTexture3);
    }
    public override void AddRenderPasses(ScriptableRenderer renderer, ref RenderingData renderingData)
    {
        SetupRenderPasses(renderer, renderingData);
        renderer.EnqueuePass(SSPRpass);
    }
    public override void SetupRenderPasses(ScriptableRenderer renderer, in RenderingData renderingData)
    {
        base.SetupRenderPasses(renderer, renderingData);
        SSPRpass.SetUp();
    }
    protected override void Dispose(bool disposing)
    {
        base.Dispose(disposing);
        SSPRpass.Dispose();
    }
}
public class SSPRPass : ScriptableRenderPass
{
    private Material material;
    private string PassName;
    private RenderTexture renderTexture1;
    private RTHandle RTHandle1;
    private RTHandle RTHandle2;
    private RTHandle RTHandle3;
    private class PassData
    {
        internal TextureHandle textureHandle1,textureHandle2,textureHandle3;
        internal Material material;
    }
    public SSPRPass(Material getMaterial ,RenderPassEvent getRenderPassEvent,string getPassName,Texture2D texture2D,RenderTexture renderTexture1,RenderTexture renderTexture2)
    {
        material = getMaterial;
        renderPassEvent = getRenderPassEvent;
        profilingSampler = new ProfilingSampler(getPassName);
        PassName = getPassName;

        RTHandle1 = RTHandles.Alloc(texture2D);

        RTHandle3 = RTHandles.Alloc(renderTexture2);

        this.renderTexture1 = renderTexture1;
    }
    public override void RecordRenderGraph(RenderGraph renderGraph, ContextContainer frameData)
    {
        var resourceData = frameData.Get<UniversalResourceData>();
        TextureHandle cameraColorHandle = resourceData.activeColorTexture;
        using (var builder = renderGraph.AddRasterRenderPass<PassData>(PassName, out var passData))
        {
            passData.material = material;
            passData.textureHandle1 = renderGraph.ImportTexture(RTHandle1);
            passData.textureHandle2 = cameraColorHandle;
            passData.textureHandle3 = renderGraph.ImportTexture(RTHandle3);
            builder.UseTexture(passData.textureHandle1);
            builder.UseTexture(passData.textureHandle2);
            builder.SetRenderAttachment(passData.textureHandle3, 0, AccessFlags.ReadWrite);
            builder.SetRenderFunc<PassData>((PassData data, RasterGraphContext ctx) =>
            {

                data.material.SetTexture("AA", data.textureHandle1);
                data.material.SetTexture("BB", data.textureHandle2);

            });
        }
    }
    public void SetUp()
    {
        Texture2D texture2D1 = new Texture2D(renderTexture1.width, renderTexture1.height);
        Graphics.ConvertTexture(renderTexture1, texture2D1);
        RTHandle2 = RTHandles.Alloc(texture2D1);
    }

    public void Dispose()
    {
        if (RTHandle1 != null) RTHandle1.Release();
        if (RTHandle2 != null) RTHandle2.Release();
        if (RTHandle3 != null) RTHandle3.Release();

    }
}

测试shader中有正确传递AABB两张贴图

Shader "Unlit/SSPR"
{
    Properties
    {
        AA("_BlitTexture",2D) = "white"{}
        BB("_BlitTexture",2D) = "white"{}
    }
    SubShader
    {
        Tags { "RenderType"="Opaque" }
        LOD 100

        Pass
        {
            CGPROGRAM
            #pragma vertex vert
            #pragma fragment frag
            // make fog work
            #pragma multi_compile_fog

            #include "UnityCG.cginc"
            float4 _BlitScaleBias;
            struct appdata
            {
                float4 vertex : POSITION;
                float2 uv : TEXCOORD0;
            };

            struct v2f
            {
                float2 uv : TEXCOORD0;
                UNITY_FOG_COORDS(1)
                float4 vertex : SV_POSITION;
            };

            sampler2D AA;
            sampler2D BB;

            v2f vert (appdata v)
            {
                v2f o;
                o.vertex = UnityObjectToClipPos(v.vertex);
                o.uv = v.uv;
                UNITY_TRANSFER_FOG(o,o.vertex);
                return o;
            }

            fixed4 frag (v2f i) : SV_Target
            {
                fixed4 aa = tex2D(AA, i.uv);
                fixed4 bb = tex2D(BB, i.uv);
                return aa * bb;
            }
            ENDCG
        }
    }
}

Answer 1

下午好🌅🌅🌅
本答案参考通义千问

在Unity URP 6+版本中，实现后处理抓屏功能（即从渲染管线中获取屏幕图像）需要正确使用ScriptableRenderPass和RenderGraph机制。你提到的“屏幕全黑”或“报错”，通常是因为资源未正确分配、纹理未正确绑定，或者渲染流程顺序错误。

下面我将详细说明如何在URP 6+中正确实现后处理抓屏，并针对你的代码进行分析和修正。

---

✅ 问题分析

你提供的代码存在以下问题：

1. RTHandle的使用方式不正确：RTHandles.Alloc()应该用于分配临时纹理，而不是直接使用Texture2D。
2. Shader参数传递错误：你在RecordRenderGraph中设置的是data.material.SetTexture("AA", data.textureHandle1);，但textureHandle1是一个TextureHandle，而SetTexture需要的是Texture类型。
3. 没有正确设置渲染目标：在RecordRenderGraph中，你可能没有正确设置渲染目标或输出通道。
4. 缺少对RenderTarget的引用：你需要确保renderTexture1等变量是通过RTHandle分配的。

---

✅ 解决方案

1. 修改SSPRPass类中的记录方法

public override void RecordRenderGraph(RenderGraph renderGraph, ContextContainer frameData)
{
    var resourceData = frameData.Get<UniversalResourceData>();
    TextureHandle cameraColorHandle = resourceData.activeColorTexture;

    using (var builder = renderGraph.AddRasterRenderPass<PassData>(PassName, out var passData))
    {
        // 正确导入纹理
        passData.textureHandle1 = renderGraph.ImportTexture(RTHandle1);
        passData.textureHandle2 = cameraColorHandle;
        passData.textureHandle3 = renderGraph.ImportTexture(RTHandle3);

        // 使用这些纹理
        builder.UseTexture(passData.textureHandle1);
        builder.UseTexture(passData.textureHandle2);
        builder.UseTexture(passData.textureHandle3);

        // 设置渲染目标
        builder.SetRenderAttachment(passData.textureHandle3, 0, AccessFlags.ReadWrite);

        // 设置渲染函数
        builder.SetRenderFunc((PassData data, RasterGraphContext ctx) =>
        {
            // 正确传递纹理
            data.material.SetTexture("AA", data.textureHandle1);
            data.material.SetTexture("BB", data.textureHandle2);
        });
    }
}

注意：SetTexture("AA", data.textureHandle1) 中 data.textureHandle1 是一个 TextureHandle，不是 Texture，所以这个写法是错误的。你应该用 TextureHandle 的 .GetTexture() 方法来获取实际的 Texture。

---

2. 修正 Shader 中的参数名称

确保你的Shader中使用了正确的名称，例如：

Properties
{
    _AA ("AA", 2D) = "white"{}
    _BB ("BB", 2D) = "white"{}
}

然后在Shader中使用：

sampler2D _AA;
sampler2D _BB;

---

3. 修正 SSPRPass 类中的 SetUp 方法

不要使用 Graphics.ConvertTexture，而是直接通过 RTHandle 获取纹理：

public void SetUp()
{
    // 不要创建新的 Texture2D，而是直接通过 RTHandle 获取
    Texture2D texture2D1 = RTHandle1.Texture;
    // 或者你可以将其作为纹理使用
}

---

4. 确保 RenderTexture 被正确分配

在 Create() 方法中，确保 RTHandle1, RTHandle2, RTHandle3 是通过 RTHandles.Alloc() 分配的：

public override void Create()
{
    // 假设 renderTexture1 是一个 RenderTexture
    RTHandle1 = RTHandles.Alloc(renderTexture1.width, renderTexture1.height, 
        format: RenderTextureFormat.Default, 
        colorFormat: RenderTextureFormat.Default, 
        depthFormat: DepthFormat.None);

    RTHandle2 = RTHandles.Alloc(renderTexture1.width, renderTexture1.height, 
        format: RenderTextureFormat.Default, 
        colorFormat: RenderTextureFormat.Default, 
        depthFormat: DepthFormat.None);

    RTHandle3 = RTHandles.Alloc(renderTexture1.width, renderTexture1.height, 
        format: RenderTextureFormat.Default, 
        colorFormat: RenderTextureFormat.Default, 
        depthFormat: DepthFormat.None);

    SSPRpass = new SSPRPass(material, renderPassEvent, passName, RTHandle1, RTHandle2, RTHandle3);
}

---

5. 确保在 AddRenderPasses 中正确调用 Setup

public override void AddRenderPasses(ScriptableRenderer renderer, ref RenderingData renderingData)
{
    SetupRenderPasses(renderer, renderingData);
    renderer.EnqueuePass(SSPRpass);
}

---

✅ 最终修正后的完整代码

1. SSPRFeature.cs

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

public class SSPRFeature : ScriptableRendererFeature
{
    public Material material;
    public string passName;
    public RenderPassEvent renderPassEvent;

    private SSPRPass ssprPass;

    public override void Create()
    {
        ssprPass = new SSPRPass(material, renderPassEvent, passName);
    }

    public override void AddRenderPasses(ScriptableRenderer renderer, ref RenderingData renderingData)
    {
        SetupRenderPasses(renderer, renderingData);
        renderer.EnqueuePass(ssprPass);
    }

    public override void SetupRenderPasses(ScriptableRenderer renderer, in RenderingData renderingData)
    {
        base.SetupRenderPasses(renderer, renderingData);
        ssprPass.SetUp();
    }

    protected override void Dispose(bool disposing)
    {
        base.Dispose(disposing);
        ssprPass.Dispose();
    }
}

---

2. SSPRPass.cs

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

public class SSPRPass : ScriptableRenderPass
{
    private Material material;
    private string passName;
    private RTHandle rtHandle1, rtHandle2, rtHandle3;

    public SSPRPass(Material material, RenderPassEvent renderPassEvent, string passName)
    {
        this.material = material;
        this.passName = passName;
        renderPassEvent = renderPassEvent;
        profilingSampler = new ProfilingSampler(passName);
    }

    public override void RecordRenderGraph(RenderGraph renderGraph, ContextContainer frameData)
    {
        var resourceData = frameData.Get<UniversalResourceData>();
        TextureHandle cameraColorHandle = resourceData.activeColorTexture;

        using (var builder = renderGraph.AddRasterRenderPass<PassData>(passName, out var passData))
        {
            passData.textureHandle1 = renderGraph.ImportTexture(rtHandle1);
            passData.textureHandle2 = cameraColorHandle;
            passData.textureHandle3 = renderGraph.ImportTexture(rtHandle3);

            builder.UseTexture(passData.textureHandle1);
            builder.UseTexture(passData.textureHandle2);
            builder.UseTexture(passData.textureHandle3);

            builder.SetRenderAttachment(passData.textureHandle3, 0, AccessFlags.ReadWrite);

            builder.SetRenderFunc((PassData data, RasterGraphContext ctx) =>
            {
                // 正确传递纹理
                data.material.SetTexture("AA", data.textureHandle1.GetTexture());
                data.material.SetTexture("BB", data.textureHandle2.GetTexture());
            });
        }
    }

    public void SetUp()
    {
        rtHandle1 = RTHandles.Alloc(1024, 768, RenderTextureFormat.Default, 
            colorFormat: RenderTextureFormat.Default, 
            depthFormat: DepthFormat.None);

        rtHandle2 = RTHandles.Alloc(1024, 768, RenderTextureFormat.Default, 
            colorFormat: RenderTextureFormat.Default, 
            depthFormat: DepthFormat.None);

        rtHandle3 = RTHandles.Alloc(1024, 768, RenderTextureFormat.Default, 
            colorFormat: RenderTextureFormat.Default, 
            depthFormat: DepthFormat.None);
    }

    public void Dispose()
    {
        if (rtHandle1 != null) rtHandle1.Release();
        if (rtHandle2 != null) rtHandle2.Release();
        if (rtHandle3 != null) rtHandle3.Release();
    }

    private class PassData
    {
        internal TextureHandle textureHandle1, textureHandle2, textureHandle3;
        internal Material material;
    }
}

---

✅ 总结

• 正确使用 RTHandle 是关键。
• 避免使用 Graphics.ConvertTexture，改用 RTHandle 直接获取纹理。
• Shader 参数名称必须与 C# 中 SetTexture 的名称一致。
• 确保渲染流程顺序正确，避免屏幕全黑。

---

✅ 测试建议

在脚本中可以添加如下代码测试是否成功抓屏：

void OnPostRender()
{
    Texture2D screenTex = new Texture2D(Screen.width, Screen.height);
    RenderTexture.active = renderTexture1;
    screenTex.ReadPixels(new Rect(0, 0, Screen.width, Screen.height), 0, 0);
    screenTex.Apply();
    Debug.Log("Screen captured!");
}

---

如果你还有其他问题，比如如何将抓取的纹理保存为图片，也可以继续问我！