// Copyright 1998-2014 Epic Games, Inc. All Rights Reserved.

/*=============================================================================
	PostProcessSceneColorFringe.usf: PostProcessing scene color fringe shader
=============================================================================*/

#include "Common.usf"
#include "PostProcessCommon.usf"

// can be optimized
float2 ScreenPosToUV(float2 ScreenPos)
{
	return (ScreenPos * ScreenPosToPixel.xy + ScreenPosToPixel.zw) * PostprocessInput0Size.zw;
}

float2 UVToScreenPos(float2 UV)
{
	return (UV * PostprocessInput0Size.xy - ScreenPosToPixel.zw) / ScreenPosToPixel.xy;
}

// .rgb:SceneFringeIntensity for RGB, .a:unused
float4 FringeUVParams;

// vertex shader
void MainVS(
	in float4 InPosition : ATTRIBUTE0,
	in float2 InTexCoord : ATTRIBUTE1,
	out float4 OutUV01 : TEXCOORD0,
	out float2 OutUV2 : TEXCOORD1,
	out float4 OutPosition : SV_POSITION
	)
{
	DrawRectangle(InPosition, InTexCoord, OutPosition, InTexCoord);

	float2 ScreenPos = UVToScreenPos(InTexCoord);
	 
	float2 UV0 = ScreenPosToUV(ScreenPos * FringeUVParams.r);
	float2 UV1 = ScreenPosToUV(ScreenPos * FringeUVParams.g);
	float2 UV2 = ScreenPosToUV(ScreenPos * FringeUVParams.b);

	// pack in float4
	OutUV01 = float4(UV0, UV1);
	OutUV2 = UV2;
}

// .rgb:color multiplier, .a:unused
float4 FringeColorParams[3];

// pixel shader
void MainPS(
	in float4 UV01 : TEXCOORD0,
	in float2 UV2 : TEXCOORD1,
	out float4 OutColor : SV_Target0
	)
{

	// unpack from float4
	float2 UV0 = UV01.xy;
	float2 UV1 = UV01.zw;

	// combine 3 samples with a different RGB shift
	OutColor = 0;
	OutColor.rgb += Texture2DSample(PostprocessInput0, PostprocessInput0Sampler, UV0).rgb * FringeColorParams[0].rgb;
	OutColor.rgb += Texture2DSample(PostprocessInput0, PostprocessInput0Sampler, UV1).rgb * FringeColorParams[1].rgb;
	OutColor.rgb += Texture2DSample(PostprocessInput0, PostprocessInput0Sampler, UV2).rgb * FringeColorParams[2].rgb;
}