Custom Node using struct function has error which "External function used in non-library profile"

Development Programming & Scripting
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1

I have one custom node.
My .ush & .usf in here

.ush

#ifndef __CARDSHADER_USH__

#define __CARDSHADER_USH__

struct RenderFunc

{

    float2 ParallaxMapping(float2 uv,float3 viewDir,float heightScale);

    float4 FinalRender();

};

#endif

.usf

#include "CardShader.ush"




float2 RenderFunc::ParallaxMapping(float2 uv,float3 viewDir,float heightScale) {

    float2 offset = viewDir.xy / viewDir.z;

    offset = offset * heightScale;

    return uv - offset;

}




float4 RenderFunc::Output() {

    float4 BackColor = Texture2DSample(_Back,_BackSampler, ParallaxMapping(_uv, _ViewDirWs, 0.2));

    float4 BackgroundColor = Texture2DSample(_Background, _BackgroundSampler, ParallaxMapping(_uv, _ViewDirWs, 0.4));

    float4 FrontColor = Texture2DSample(_Front, _FrontSampler, ParallaxMapping(_uv, _ViewDirWs, 0.6));

    float4 BorderColor = Texture2DSample(_Border, _BorderSampler, ParallaxMapping(_uv, _ViewDirWs, 0.7));




    float4 finalCol = float4(0,0,0,1);

    finalCol = BackgroundColor;

    finalCol = lerp(finalCol, FrontColor, FrontColor.a);

    finalCol += BorderColor;

    return finalCol;

}

custom node



 "/Shaders/CardShader.ush"

RenderFunc _func;
_func.FinalRender();

return 0;

Output:
[SM6] Shader debug info dumped to: “D:\qsw\GameWorkSpace\UE\RTR_Learning\Saved\ShaderDebugInfo\PCD3D_SM6\M_CardMat_61540b8bec78582b\Default\FLocalVertexFactory\FLumenCardPS\0”

D:\UE_5.8\Engine\Shaders\Private\MaterialTemplate.ush(3749,7): Shader FLumenCardPS, Permutation 0, VF FLocalVertexFactory:
/Engine/Generated/Material.ush:3749:7: note: used here
_func.FinalRender();
^
error: External function used in non-library profile: \01?FinalRender@RenderFunc@?1??CustomExpression0@@YA?AV?$vector@M$03@@UFMaterialPixelParameters@@V?$Texture2D@V?$vector@M$03@@@@USamplerState@@121212V?$vector@M$01@@V?$vector@M$02@@@Z@QAA?AV3@XZ

I don’t know how to resolve it really.
Please me!