// Copyright Epic Games, Inc. All Rights Reserved.

#include "Common.ush"
#include "ScreenPass.ush"
#include "PostProcessHistogramCommon.ush"

SCREEN_PASS_TEXTURE_VIEWPORT(Input)
SCREEN_PASS_TEXTURE_VIEWPORT(Output)

Texture2D InputTexture;

StructuredBuffer<float4> EyeAdaptationBuffer;

Texture3D LumBilateralGrid;
Texture2D BlurredLogLum;

SamplerState TextureSampler;

RWTexture2D<float> OutputFloat;
RWTexture2D<float4> OutputFloat4;

[numthreads(THREADGROUP_SIZEX, THREADGROUP_SIZEY, 1)]
void SetupLogLuminanceCS(uint3 DispatchThreadId : SV_DispatchThreadID)
{
	float3 SceneColor = InputTexture.Load(uint3(Input_ViewportMin + DispatchThreadId.xy, 0)).rgb * View.OneOverPreExposure;
	float LuminanceVal = CalculateEyeAdaptationLuminance(SceneColor);
	OutputFloat[DispatchThreadId.xy] = log2(LuminanceVal);
}

[numthreads(THREADGROUP_SIZEX, THREADGROUP_SIZEY, 1)]
void ApplyLocalExposureCS(uint2 DispatchThreadId : SV_DispatchThreadID)
{
	uint2 OutputPixelPos = DispatchThreadId + Output_ViewportMin;

	if (all(OutputPixelPos < Output_ViewportMax))
	{
		const float2 UV = (DispatchThreadId + 0.5f) * Output_ExtentInverse;

		float2 ExposureScaleMiddleGrey = EyeAdaptationBuffer[0].xw;
		float ExposureScale = ExposureScaleMiddleGrey.x;
		float MiddleGreyLumValue = log2(0.18 * ExposureScaleMiddleGrey.y * LocalExposure_MiddleGreyExposureCompensation);

		float4 SceneColor = InputTexture.Load(uint3(DispatchThreadId + Input_ViewportMin, 0));

		float LuminanceVal = CalculateEyeAdaptationLuminance(SceneColor.rgb * View.OneOverPreExposure);
		float LogLuminance = log2(LuminanceVal);

		float BaseLogLum = CalculateBaseLogLuminance(LogLuminance, LocalExposure_BlurredLuminanceBlend, ExposureScale, UV, LumBilateralGrid, BlurredLogLum, TextureSampler, TextureSampler);
		float LocalExposure = CalculateLocalExposure(LogLuminance + log2(ExposureScale), BaseLogLum, MiddleGreyLumValue, LocalExposure_HighlightContrastScale, LocalExposure_ShadowContrastScale, LocalExposure_DetailStrength);

		SceneColor.rgb *= LocalExposure;

		OutputFloat4[OutputPixelPos] = SceneColor;
	}
}