首先需要在unity中开启屏幕图像开关才可以使用该纹理

同样只有不透明对象才能被渲染到屏幕图像中 

若想要该对象不被渲染到屏幕图像中，可以将其Shader的渲染队列改为 "Queue" = "Transparent"

如何在Shader中使用_CameraOpaqueTexture？

使用模型的屏幕空间坐标采样屏幕图像的具体方法看前一篇

Shader"unity/GrabTex"
{
	Properties
	{
		
	 }

	SubShader
	{
		Tags
		{
			"RenderPipeline"="UniversalPipeline"
			"Queue" = "Transparent"
		 }
		Pass
		{
			HLSLPROGRAM

			#pragma vertex vert
			#pragma fragment frag

			#include "Packages/com.unity.render-pipelines.core/ShaderLibrary/Common.hlsl"
			#include "Packages/com.unity.render-pipelines.core/ShaderLibrary/Color.hlsl"
            #include "Packages/com.unity.render-pipelines.universal/ShaderLibrary/Input.hlsl"

			TEXTURE2D(_CameraOpaqueTexture);
			SAMPLER(sampler_CameraOpaqueTexture);

			struct Attributes
			{
				float4 positionOS : POSITION;
				float2 uv : TEXCOORD;
			 };

			struct Varyings
			{
				float4 positionCS : SV_POSITION;
				float2 uv : TEXCOORD;
			 };

			Varyings vert(Attributes v)
			{
				Varyings o = (Varyings)0;
				o.positionCS = TransformObjectToHClip(v.positionOS);
				o.uv = v.uv;
				return o;
			 }

			 float4 frag(Varyings i):SV_Target
			 {
				 float2 screenUV = i.positionCS/_ScreenParams.xy;

				 float4 ScreenTex = SAMPLE_TEXTURE2D(_CameraOpaqueTexture,sampler_CameraOpaqueTexture,screenUV);

				 return ScreenTex;
			  }

			ENDHLSL
		 }
	 }
 }