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

/*=============================================================================
	PostProcessVisualizeGBuffer.usf: PostProcessing shader to visualize the GBuffer
=============================================================================*/

#include "Common.usf"
#include "PostProcessCommon.usf"
#include "DeferredShadingCommon.usf"
#include "PostProcessHistogramCommon.usf"

/** Main pixel shader function */
void MainPS(float4 UVAndScreenPos : TEXCOORD0, out float4 OutColor : SV_Target0)
{
	float Alpha = 1;

#if DRAWING_TILE
	int2 PixelPos = (int2)(UVAndScreenPos.zw * ScreenPosToPixel.xy + ScreenPosToPixel.zw + 0.5f);

	// half viewport size
	int2 HalfInsetSize = (int2)(ViewportSize.xy / 2);
	// quarter viewport size
	int2 QuarterInsetSize = (int2)(ViewportSize.xy / 4);

	// 16 tiles over the full viewport
	int2 QuarterTileXY = (int2)((uint2)PixelPos / QuarterInsetSize);
	// pixel position within a quartertile 
	int2 QuarterTileLocalPos = PixelPos - QuarterTileXY * QuarterInsetSize;

	const int Border1 = 10;
	const int Border2 = 8;
	float BorderDistance = ComputeDistanceToRect(QuarterTileLocalPos, int2(0, 0) + Border1.xx, QuarterInsetSize - 2 * Border1.xx);
	Alpha = 1 - saturate((BorderDistance - Border2.x) * 0.5f);
#endif

	OutColor = float4(Texture2DSample(PostprocessInput0, PostprocessInput0Sampler, UVAndScreenPos.xy).rgb, Alpha);
}