UnrealEngineUWP/Engine/Shaders/GammaCorrection.usf

// Copyright 1998-2015 Epic Games, Inc. All Rights Reserved.

/*=============================================================================
	GammaCorrection.usf: Gamma correcting the scene color buffer
=============================================================================*/

#include "Common.usf"

// vertex shader entry point
void MainVS(
	in float4 InPosition : ATTRIBUTE0,
	in float2 InTexCoord : ATTRIBUTE1,
	out float2 OutTexCoord : TEXCOORD0,
	out float4 OutPosition : SV_POSITION
	)
{
	DrawRectangle(InPosition, InTexCoord, OutPosition, OutTexCoord);
}

half3 ColorScale;
half4 OverlayColor;
half InverseGamma;

half3 TonemapAndGammaCorrect(half3 LinearColor)
{
	half3 GammaColor;

	// no tonemapper
	{
		GammaColor = pow(LinearColor, InverseGamma);
	}

	// in all cases it's good to clamp into the 0..1 range (e.g for LUT color grading)
	GammaColor = saturate(GammaColor);

	return GammaColor;
}

// pixel shader entry point
void MainPS(float2 UV : TEXCOORD0, out float4 OutColor : SV_Target0)
{
	half4 LinearColor = Texture2DSample(SceneColorTexture, SceneColorTextureSampler, UV);
	half3 LDRColor = TonemapAndGammaCorrect(LinearColor.rgb);
	
	// blend with custom LDR color, used for Fade track in Matinee
	LDRColor = lerp(LDRColor * ColorScale, OverlayColor.rgb, OverlayColor.a);
	
	// RETURN_COLOR not needed unless writing to SceneColor
	OutColor = float4(LDRColor, LinearColor.a);
}