Question Using custom node with shader graph node code

hey, there! any one to try to use the shader graph node code within custom function node ( hlsl ). No error I got but somehow, using SHADERGRAPH_SAMPLE_SCENE_COLOR does not seem to be return scene color on 2019.3. Just using scene color node is working fine. Is there anything missing?

    

    float3 sum = float3(0,0,0);

    float4 UV = float4(0,0,0,0);

    float val = 1;



    for (int i = 0; i < sampleCount; i++) {

        if ( i < sampleCount/2 ) {

            val = -1;

        }

        UV = float4(screenPosUV + float4(offsets*val, 0, 0));

        float3 sampleColor = SHADERGRAPH_SAMPLE_SCENE_COLOR(UV);

        sum = sampleColor;

    };



    sum = sum/sampleCount;

    result.rgb = sum;

    result.a = 1;

 

I'd like this too. Perhaps something needs to be included to give a custom function access to the opaque texture (in URP) besides making it a transparent graph?