How to displays camera depth target as color target by SRP?

Unity Engine
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1

Hi, i am learning SRP and want to display camera depth target on the screen. ( Just like some kind of image effect ), but i really don’t know how to do it.

I add two pass to my srp, the first one just write depth by

using (var builder = renderGraph.AddRasterRenderPass<SSShadowMapData>("Write SSShadowMap", out var passData,
                       m_ssShadowMapProfilingSampler))
            {
                RendererListDesc ssShadowPassDesc =
                    new RendererListDesc(m_ssShadowMapID, cameraData.cullingResults, cameraData.camera);
                ssShadowPassDesc.sortingCriteria = SortingCriteria.CommonOpaque;
                ssShadowPassDesc.renderQueueRange = RenderQueueRange.opaque;

                passData.m_RendererListHandle = renderGraph.CreateRendererList(ssShadowPassDesc);

                builder.UseRendererList(passData.m_RendererListHandle);

                if (m_BackbufferDepthHandle.IsValid())
                    builder.SetRenderAttachmentDepth(m_BackbufferDepthHandle, AccessFlags.Write);
                
                builder.AllowPassCulling(false);
                builder.AllowGlobalStateModification(true);
                
                builder.SetRenderFunc<SSShadowMapData>(SSShadowMapRenderFunc);
            }

The second one tries to display “m_BackbufferDepthHandle” with

using (var builder = renderGraph.AddRasterRenderPass<TestBlitData>("Test SSShadowMap", out var passData,
                       m_TestBlitSampler))
            {
                if (!m_BackbufferDepthHandle.IsValid())
                    return;
                
                passData.depthTex = m_BackbufferDepthHandle;
                
                if(m_BackbufferColorHandle.IsValid())
                    builder.SetRenderAttachment(m_BackbufferColorHandle, 0, AccessFlags.Write);
                
                builder.AllowPassCulling(false);
                builder.AllowGlobalStateModification(true);
                
                builder.SetRenderFunc<TestBlitData>((data, context) =>
                {
                    context.cmd.SetGlobalTexture("_TestDepthTex", data.depthTex);
                    context.cmd.DrawProcedural(Matrix4x4.identity, m_BasicUnlitMat, 0, MeshTopology.Triangles, 6);
                });
            }

And the shader

SubShader
    {
        Tags
        {
            "RenderType"="Transparent"
            "RenderQueue"="Transparent"
            "RenderPipeline" = "LiteRenderPipeline"
        }

        ZTest Always
        ZWrite Off
        Cull Off
        
        Pass
        {
            HLSLPROGRAM
            #pragma vertex vert
            #pragma fragment frag

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

            struct Attributes
            {
                uint vertexID : SV_VertexID; // 输入的顶点 ID
            };

            struct Varyings
            {
                float2 uv : TEXCOORD0;
                float4 positionCS : SV_POSITION; // 裁剪空间中的顶点位置
            };

            TEXTURE2D(_TestDepthTex);
            SAMPLER(sampler_TestDepthTex);

            Varyings vert(Attributes input)
            {
                Varyings output;
                
                float2 uv = float2(
                    float(input.vertexID == 1 || input.vertexID == 4 || input.vertexID == 5),
                    float(input.vertexID == 2 || input.vertexID == 3 || input.vertexID == 5)
                );
                output.positionCS = float4(uv * 2.0 - 1.0, 0, 1);
                output.uv = uv;
                
                return output;
            }

            float4 frag(Varyings input) : SV_Target
            {
                float depth = SAMPLE_DEPTH_TEXTURE(_TestDepthTex, sample_TestDepthTex, input.uv).r;
                
                #if UNITY_REVERSED_Z
                    depth = 1.0 - depth;
                #endif

                return float4(depth / 5, 0, 0, 1); // divide 5 just because i want to see more clear
            }
            ENDHLSL
           
        }

The result is that it seems do not write anything inside the depth target, please help if somebody know how to do it, if you need more detail, i can provide more, Anybody, please help !