// Copyright 1998-2017 Epic Games, Inc. All Rights Reserved.

/*=============================================================================
	PostProcessLensFlares.usf: PostProcessing Lens Flares.
=============================================================================*/

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

// RGB:color, a:unused
float4 FlareColor; 
// UV is in 0..1 range but the viewport might not cover the full screen
float2 TexScale;

// pixel shader, can be optimized by using additive blending
void CopyPS(noperspective float4 InUV : TEXCOORD0, out float4 OutColor : SV_Target0)
{
#ifdef CLEAR_REGION
	OutColor = float4(0.f, 0.f, 0.f, 0.f);
#else	
	OutColor = Texture2DSample(PostprocessInput0, PostprocessInput0Sampler, InUV.xy);
#endif 
}

// pixel shader entry point
void MainPS(in noperspective float4 UVAndScreenPos : TEXCOORD0, out float4 OutColor : SV_Target0)
{
	float2 UV = UVAndScreenPos.xy;
	float2 ScreenPos = UVAndScreenPos.zw;

	// circular shape to mark the screen border (needed but can be implemented with different math)
	float ScreenborderMask = DiscMask(ScreenPos);

	// extra circular shape aligned to the screen to mask big lens flares
	ScreenborderMask *= DiscMask(ScreenPos * 0.8f);

	OutColor.rgb = Texture2DSample(PostprocessInput1, PostprocessInput1Sampler, UV).rgb * FlareColor.rgb * ScreenborderMask;
	OutColor.a = 0;
}