//--------------------------------------------------------------------------------------------------
// Definitions
//--------------------------------------------------------------------------------------------------

// #pragma enable_d3d11_debug_symbols
#pragma only_renderers d3d11 playstation xboxone xboxseries vulkan metal switch switch2

#pragma kernel Downsample

//--------------------------------------------------------------------------------------------------
// Included headers
//--------------------------------------------------------------------------------------------------

#include "Packages/com.unity.render-pipelines.core/ShaderLibrary/Common.hlsl"
#include "Packages/com.unity.render-pipelines.high-definition/Runtime/ShaderLibrary/ShaderVariables.hlsl"

//--------------------------------------------------------------------------------------------------
// Inputs & outputs
//--------------------------------------------------------------------------------------------------
TEXTURE2D_X(_SourceTexture);
RW_TEXTURE2D_X(float4, _OutputTexture);

int _SssDownsampleSteps;

#define GROUP_SIZE 8

[numthreads(GROUP_SIZE, GROUP_SIZE, 1)]
void Downsample(uint3 dispatchThreadId : SV_DispatchThreadID)
{
    uint2 positionSS = dispatchThreadId.xy;
    uint scale1d = 1u << _SssDownsampleSteps;

    // Downsample will just randomly select one of the source samples
    float rand = InterleavedGradientNoise(positionSS, _FrameCount);
    uint index = uint(rand * scale1d * scale1d);

    uint2 inputSS = (positionSS * scale1d) + uint2(index / scale1d, index % scale1d);

    float4 value = LOAD_TEXTURE2D_X(_SourceTexture, inputSS);
    _OutputTexture[COORD_TEXTURE2D_X(positionSS)] = value;
}