Shader "Hidden/CopyDepth"
{
    SubShader
    {
        ZTest Off
        ZWrite Off
        
        Pass
        {
            HLSLPROGRAM
            #pragma vertex Vertex
            #pragma fragment DownsampleDepthFrag
#pragma enable_d3d11_debug_symbols
            #include "Packages/com.unity.render-pipelines.universal/ShaderLibrary/Core.hlsl"

            struct Attributes
            {
                float4 positionOS   : POSITION;
                float2 texcoord     : TEXCOORD0;
            };

            struct Varyings
            {
                float2 uv                      : TEXCOORD0;
                float4 positionCS               : SV_POSITION;
            };

            Varyings Vertex(Attributes input)
            {
                Varyings output = (Varyings)0;
                output.positionCS = TransformObjectToHClip(input.positionOS.xyz);
                output.uv = input.texcoord;
                return output;
            }
        
            #if UNITY_REVERSED_Z
            # define MIN_DEPTH(l, r) min(l, r)
            #else
            # define MIN_DEPTH(l, r) max(l, r)
            #endif

            TEXTURE2D_FLOAT(_InputDepth);
            SAMPLER(sampler_InputDepth);
            float4 _InputScaleAndMaxIndex;//xy: inputeTexsize/outputTextureSize , zw:textureSize - 1 

            half4 DownsampleDepthFrag(Varyings input) : SV_Target
            {
                int2 texCrood = int2(input.positionCS.xy) * _InputScaleAndMaxIndex.xy;
                uint2 maxIndex = _InputScaleAndMaxIndex.zw;
                int2 texCrood00 = min(texCrood + uint2(0, 0), maxIndex);
                int2 texCrood10 = min(texCrood + uint2(1, 0), maxIndex);
                int2 texCrood01 = min(texCrood + uint2(0, 1), maxIndex);
                int2 texCrood11 = min(texCrood + uint2(1, 1), maxIndex);
                float p00 = LOAD_TEXTURE2D_LOD(_InputDepth,texCrood00,0);
                float p01 = LOAD_TEXTURE2D_LOD(_InputDepth,texCrood10,0);
                float p10 = LOAD_TEXTURE2D_LOD(_InputDepth,texCrood01,0);
                float p11 = LOAD_TEXTURE2D_LOD(_InputDepth,texCrood11,0);
                return MIN_DEPTH(MIN_DEPTH(p00 ,p01), MIN_DEPTH(p10, p11));
            }
            
            ENDHLSL
        }

        Pass
        {
            HLSLPROGRAM
            #pragma vertex Vertex
            #pragma fragment CopyDepthFrag

            #include "Packages/com.unity.render-pipelines.universal/ShaderLibrary/Core.hlsl"

            struct Attributes
            {
                float4 positionOS   : POSITION;
                float2 texcoord     : TEXCOORD0;
            };

            struct Varyings
            {
                float2 uv                      : TEXCOORD0;
                float4 positionCS               : SV_POSITION;
            };

            Varyings Vertex(Attributes input)
            {
                Varyings output = (Varyings)0;
                output.positionCS = TransformObjectToHClip(input.positionOS.xyz);
                output.uv = input.texcoord;
                return output;
            }
        
            #if UNITY_REVERSED_Z
            # define MIN_DEPTH(l, r) min(l, r)
            #else
            # define MIN_DEPTH(l, r) max(l, r)
            #endif

            TEXTURE2D_FLOAT(_InputDepth);
            SAMPLER(sampler_InputDepth);

            half4 CopyDepthFrag(Varyings input) : SV_Target
            {
                return  SAMPLE_TEXTURE2D(_InputDepth, sampler_InputDepth, input.uv);
            }
      
            ENDHLSL
        }
    }
}