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

/*=============================================================================
	ReflectionEnvironmentComputeShaders - functionality to apply local cubemaps.
=============================================================================*/
  
#include "Common.usf"
#include "DeferredShadingCommon.usf"  
#include "BRDF.usf"
#include "ReflectionEnvironmentShared.usf"

#if TILED_DEFERRED_CULL_SHADER

/** Cube map array of reflection captures. */
TextureCubeArray ReflectionEnvironmentColorTexture;
SamplerState ReflectionEnvironmentColorSampler;

#define THREADGROUP_TOTALSIZE (THREADGROUP_SIZEX * THREADGROUP_SIZEY)

// Workaround performance issue with shared memory bank collisions in GLSL
#if GL4_PROFILE
#define ATOMIC_REDUCTION 0
#else
#define ATOMIC_REDUCTION 0
#endif

#define VISUALIZE_OVERLAP	0

uint NumCaptures;
/** View rect min in xy, max in zw. */
uint4 ViewDimensions;

/** Min and Max depth for this tile. */
groupshared uint IntegerTileMinZ;
groupshared uint IntegerTileMaxZ;
/** Inner Min and Max depth for this tile. */
groupshared uint IntegerTileMinZ2;
groupshared uint IntegerTileMaxZ2;

/** Number of reflection captures affecting this tile, after culling. */
groupshared uint TileNumReflectionCaptures;
/** Indices into the capture data buffer of captures that affect this tile, computed by culling. */
groupshared uint TileReflectionCaptureIndices[MAX_CAPTURES];
/** Capture indices after sorting. */
groupshared uint SortedTileReflectionCaptureIndices[MAX_CAPTURES];

#if !ATOMIC_REDUCTION
groupshared float TileZ[THREADGROUP_TOTALSIZE];
#endif

void ComputeTileMinMax(uint ThreadIndex, float SceneDepth, out float MinTileZ, out float MaxTileZ, out float MinTileZ2, out float MaxTileZ2)
{
#if ATOMIC_REDUCTION

	// Initialize per-tile variables
	if (ThreadIndex == 0) 
	{
		IntegerTileMinZ = 0x7F7FFFFF;     
		IntegerTileMaxZ = 0;
		IntegerTileMinZ2 = 0x7F7FFFFF;  
		IntegerTileMaxZ2 = 0;
	}

	GroupMemoryBarrierWithGroupSync();
	
	// Use shared memory atomics to build the depth bounds for this tile
	// Each thread is assigned to a pixel at this point
	InterlockedMin(IntegerTileMinZ, asuint(SceneDepth));
	InterlockedMax(IntegerTileMaxZ, asuint(SceneDepth));

	GroupMemoryBarrierWithGroupSync();

	MinTileZ = asfloat(IntegerTileMinZ);
	MaxTileZ = asfloat(IntegerTileMaxZ);
	
	float HalfZ = .5f * (MinTileZ + MaxTileZ);

	// Compute a second min and max Z, clipped by HalfZ, so that we get two depth bounds per tile
	// This results in more conservative tile depth bounds and fewer intersections
	if (SceneDepth >= HalfZ)
	{
		InterlockedMin(IntegerTileMinZ2, asuint(SceneDepth));
	}

	if (SceneDepth <= HalfZ)
	{
		InterlockedMax(IntegerTileMaxZ2, asuint(SceneDepth));
	}

	GroupMemoryBarrierWithGroupSync();
	
	MinTileZ2 = asfloat(IntegerTileMinZ2);
	MaxTileZ2 = asfloat(IntegerTileMaxZ2);
#else

	TileZ[ThreadIndex] = SceneDepth;

	GroupMemoryBarrierWithGroupSync();

	THREADGROUP_TOTALSIZE;

	if (ThreadIndex < 32)
	{
		float Min = SceneDepth;
		float Max = SceneDepth;
		for ( int i = ThreadIndex+32; i< THREADGROUP_TOTALSIZE; i+=32)
		{
			Min = min( Min, TileZ[i]);
			Max = max( Max, TileZ[i]);
		}
		TileZ[ThreadIndex] = Min;
		TileZ[ThreadIndex + 32] = Max;
	}

	GroupMemoryBarrierWithGroupSync();

	if (ThreadIndex < 8)
	{
		float Min = TileZ[ThreadIndex];
		float Max = TileZ[ThreadIndex + 32];
		
		Min = min( Min, TileZ[ThreadIndex + 8]);
		Max = max( Max, TileZ[ThreadIndex + 40]);

		Min = min( Min, TileZ[ThreadIndex + 16]);
		Max = max( Max, TileZ[ThreadIndex + 48]);

		Min = min( Min, TileZ[ThreadIndex + 24]);
		Max = max( Max, TileZ[ThreadIndex + 56]);
		
		TileZ[ThreadIndex + 64] = Min;
		TileZ[ThreadIndex + 96] = Max;
	}

	GroupMemoryBarrierWithGroupSync();

	if (ThreadIndex == 0)
	{
		float Min = TileZ[64];
		float Max = TileZ[96];
		
		for ( int i = 1; i< 8; i++)
		{
			Min = min( Min, TileZ[i+64]);
			Max = max( Max, TileZ[i+96]);
		}
		
		IntegerTileMinZ = asuint(Min);
		IntegerTileMaxZ = asuint(Max);
	}

	GroupMemoryBarrierWithGroupSync();

	MinTileZ = asfloat(IntegerTileMinZ);
	MaxTileZ = asfloat(IntegerTileMaxZ);

	float HalfZ = .5f * (MinTileZ + MaxTileZ);

	MinTileZ2 = HalfZ;
	MaxTileZ2 = HalfZ;
#endif
}

// Culls reflection captures in the scene with the current tile
// Outputs are stored in shared memory
void DoTileCulling(uint3 GroupId, uint ThreadIndex, float MinTileZ, float MaxTileZ, float MinTileZ2, float MaxTileZ2)
{
	// Setup tile frustum planes
	float2 TileScale = float2(ViewDimensions.zw - ViewDimensions.xy) * rcp(2 * float2(THREADGROUP_SIZEX, THREADGROUP_SIZEY));
	float2 TileBias = TileScale - GroupId.xy;

    float4 C1 = float4(View.ViewToClip._11 * TileScale.x,	0.0f,								View.ViewToClip._31 * TileScale.x + TileBias.x,	0.0f);
    float4 C2 = float4(0.0f,								-View.ViewToClip._22 * TileScale.y, View.ViewToClip._32 * TileScale.y + TileBias.y,	0.0f);
    float4 C4 = float4(0.0f,								0.0f,								1.0f,											0.0f);

	// TODO transform to world space
#if ATOMIC_REDUCTION
	float4 frustumPlanes[8];
	frustumPlanes[0] = C4 - C1;
	frustumPlanes[1] = C4 + C1;
	frustumPlanes[2] = C4 - C2;
	frustumPlanes[3] = C4 + C2;
	frustumPlanes[4] = float4(0.0f, 0.0f,  1.0f, -MinTileZ);
	frustumPlanes[5] = float4(0.0f, 0.0f, -1.0f,  MaxTileZ2);
	frustumPlanes[6] = float4(0.0f, 0.0f,  1.0f, -MinTileZ2);
	frustumPlanes[7] = float4(0.0f, 0.0f, -1.0f,  MaxTileZ);
#else
	float4 frustumPlanes[6];
	frustumPlanes[0] = C4 - C1;
	frustumPlanes[1] = C4 + C1;
	frustumPlanes[2] = C4 - C2;
	frustumPlanes[3] = C4 + C2;
	frustumPlanes[4] = float4(0.0f, 0.0f,  1.0f, -MinTileZ);
	frustumPlanes[5] = float4(0.0f, 0.0f, -1.0f,  MaxTileZ);
#endif

	// Normalize tile frustum planes
	UNROLL 
	for (uint i = 0; i < 4; ++i) 
	{
		frustumPlanes[i] *= rcp(length(frustumPlanes[i].xyz));
	}

	if (ThreadIndex == 0) 
	{
		TileNumReflectionCaptures = 0;
	}

	GroupMemoryBarrierWithGroupSync();

	// Compute per-tile lists of affecting captures through bounds culling
	// Each thread now operates on a sample instead of a pixel
	LOOP
	for (uint CaptureIndex = ThreadIndex; CaptureIndex < NumCaptures && CaptureIndex < MAX_CAPTURES; CaptureIndex += THREADGROUP_TOTALSIZE)
	{
		float4 CapturePositionAndRadius = ReflectionCapture.PositionAndRadius[CaptureIndex];

		float3 BoundsViewPosition = mul(float4(CapturePositionAndRadius.xyz + View.PreViewTranslation.xyz, 1), View.TranslatedWorldToView).xyz;

		// Cull the light against the tile's frustum planes
		// Note: this has some false positives, a light that is intersecting three different axis frustum planes yet not intersecting the volume of the tile will be treated as intersecting
		bool bInTile = true;  

		// Test against the screen x and y oriented planes first
		UNROLL
		for (uint i = 0; i < 4; ++i) 
		{
			float PlaneDistance = dot(frustumPlanes[i], float4(BoundsViewPosition, 1.0f));
			bInTile = bInTile && (PlaneDistance >= -CapturePositionAndRadius.w);
		}

		BRANCH
		if (bInTile)
		{
#if ATOMIC_REDUCTION
			bool bInNearDepthRange = true;
				
			// Test against the near depth range
			UNROLL
			for (uint i = 4; i < 6; ++i)
			{
				float PlaneDistance = dot(frustumPlanes[i], float4(BoundsViewPosition, 1.0f));
				bInNearDepthRange = bInNearDepthRange && (PlaneDistance >= -CapturePositionAndRadius.w);
			}

			bool bInFarDepthRange = true;
				
			// Test against the far depth range
			UNROLL
			for (uint j = 6; j < 8; ++j)
			{
				float PlaneDistance = dot(frustumPlanes[j], float4(BoundsViewPosition, 1.0f));
				bInFarDepthRange = bInFarDepthRange && (PlaneDistance >= -CapturePositionAndRadius.w);
			}

			bool bInDepthRange = bInNearDepthRange || bInFarDepthRange;
#else
			bool bInDepthRange = true;  
				
			// Test against the depth range
			UNROLL
			for (uint i = 4; i < 6; ++i) 
			{
				float PlaneDistance = dot(frustumPlanes[i], float4(BoundsViewPosition, 1.0f));
				bInDepthRange = bInDepthRange && (PlaneDistance >= -CapturePositionAndRadius.w);
			}
#endif

			// Add this capture to the list of indices if it intersects
			BRANCH
			if (bInDepthRange)
			{
				uint ListIndex;
				InterlockedAdd(TileNumReflectionCaptures, 1U, ListIndex);
				TileReflectionCaptureIndices[ListIndex] = CaptureIndex;
			}
		}
	}

	GroupMemoryBarrierWithGroupSync();
		  
	uint NumCapturesAffectingTile = TileNumReflectionCaptures;
		 
	// Sort captures by their original capture index
	// This is necessary because the culling used InterlockedAdd to generate compacted array indices, 
	// Which rearranged the original capture order, in which the captures were sorted smallest to largest on the CPU.
	//@todo - parallel stream compaction could be faster than this
	#define SORT_CAPTURES 1
	#if SORT_CAPTURES

		// O(N^2) simple parallel sort
		LOOP
		for (uint CaptureIndex2 = ThreadIndex; CaptureIndex2 < NumCapturesAffectingTile; CaptureIndex2 += THREADGROUP_TOTALSIZE)
		{
			// Sort by original capture index
			int SortKey = TileReflectionCaptureIndices[CaptureIndex2];
			uint NumSmaller = 0;

			// Count how many items have a smaller key, so we can insert ourselves into the correct position, without requiring interaction between threads
			for (uint OtherSampleIndex = 0; OtherSampleIndex < NumCapturesAffectingTile; OtherSampleIndex++) 
			{
				int OtherSortKey = TileReflectionCaptureIndices[OtherSampleIndex];

				if (OtherSortKey < SortKey)
				{
					NumSmaller++;
				}
			}

			// Move this entry into its sorted position
			SortedTileReflectionCaptureIndices[NumSmaller] = TileReflectionCaptureIndices[CaptureIndex2];
		}

	#endif

	GroupMemoryBarrierWithGroupSync();
}

struct FLobe
{
	float4	Color;
	float3	Direction;
	float	Roughness;
	float	RayInfluance;
};

void GatherRadiance( inout FLobe Lobes[2], const uint NumLobes, float3 WorldPosition, float3 RayDirection )
{
	float LobeMip[2];

	UNROLL
	for( uint Lobe = 0; Lobe < NumLobes; Lobe++ )
	{
		LobeMip[ Lobe ] = ComputeReflectionCaptureMipFromRoughness( Lobes[ Lobe ].Roughness );
	}

	uint NumCapturesAffectingTile = TileNumReflectionCaptures;

	// Accumulate reflections from captures affecting this tile, applying largest captures first so that the smallest ones display on top
	LOOP
	for (uint TileCaptureIndex = 0; TileCaptureIndex < NumCapturesAffectingTile; TileCaptureIndex++) 
	{
		#if SORT_CAPTURES
			uint CaptureIndex = SortedTileReflectionCaptureIndices[TileCaptureIndex];
		#else
			uint CaptureIndex = TileReflectionCaptureIndices[TileCaptureIndex];
		#endif
			
		float4 CapturePositionAndRadius = ReflectionCapture.PositionAndRadius[CaptureIndex];
		float4 CaptureProperties = ReflectionCapture.CaptureProperties[CaptureIndex];
		float3 CaptureVector = WorldPosition - CapturePositionAndRadius.xyz;
		float CaptureVectorLength = sqrt(dot(CaptureVector, CaptureVector));

		BRANCH
		if (CaptureVectorLength < CapturePositionAndRadius.w)
		{
			float NormalizedDistanceToCapture = saturate(CaptureVectorLength / CapturePositionAndRadius.w);
			float3 ProjectedCaptureVector = RayDirection;

			// Fade out based on distance to capture
			float DistanceAlpha = 0;

			#define PROJECT_ONTO_SHAPE 1
			#if PROJECT_ONTO_SHAPE
					
				#define SUPPORT_PLANE 0
				#if SUPPORT_PLANE
					BRANCH
					// Plane
					if (CaptureProperties.b > 1)
					{
						float4 ImagePlane = float4(ReflectionCapture.BoxTransform[CaptureIndex][0][0], ReflectionCapture.BoxTransform[CaptureIndex][1][0], ReflectionCapture.BoxTransform[CaptureIndex][2][0], ReflectionCapture.BoxTransform[CaptureIndex][3][0]);

						float VectorDotPlaneNormal = dot(ImagePlane.xyz, RayDirection);
						// VectorDotPlaneNormal < 0 means the ray hit the front face
						BRANCH
						if (VectorDotPlaneNormal < 0)
						{
							float PlaneDistance = dot(ImagePlane.xyz, WorldPosition) - ImagePlane.w;
							// Time along the ray defined by WorldPosition + IntersectionTime * RayDirection that the intersection took place
							float IntersectionTime = -PlaneDistance / VectorDotPlaneNormal;

							BRANCH
							// Skip intersections behind the pixel being shaded
							if (IntersectionTime > 0)
							{
								// Calculate the world space intersection position
								float3 IntersectPosition = WorldPosition + IntersectionTime * ReflectionVector;
									
								float2 ReflectionUVs;
								float4 CurrentReflectionXAxis = float4(ReflectionCapture.BoxTransform[CaptureIndex][0][1], ReflectionCapture.BoxTransform[CaptureIndex][1][1], ReflectionCapture.BoxTransform[CaptureIndex][2][1], ReflectionCapture.BoxTransform[CaptureIndex][3][1]);
								float3 CurrentImageReflectionOrigin = CapturePositionAndRadius.xyz;
								float XLength = length(CurrentReflectionXAxis.xyz);
								float3 NormalizedXAxis = CurrentReflectionXAxis.xyz / XLength;
								// Calculate the quad UVs by projecting the vector from the intersection to the quad origin onto each quad axis
								ReflectionUVs.x = dot(NormalizedXAxis, IntersectPosition - CurrentImageReflectionOrigin.xyz);
								float3 ReflectionYAxis = cross(ImagePlane.xyz, NormalizedXAxis) * CurrentReflectionXAxis.w;
								ReflectionUVs.y = dot(ReflectionYAxis, IntersectPosition - CurrentImageReflectionOrigin.xyz);
								ReflectionUVs = .5f * ReflectionUVs / float2(XLength, XLength * CurrentReflectionXAxis.w) + .5f;

								ProjectedCaptureVector = IntersectPosition - CapturePositionAndRadius.xyz;

								if (ReflectionUVs.x > 0 && ReflectionUVs.x < 1 && ReflectionUVs.y > 0 && ReflectionUVs.y < 1)
								{
									CompositedLighting.rgb += 1;
								}
							}
						}
					}
					else 
				#endif
				// Box
				BRANCH if (CaptureProperties.b > 0)
				{
					// Transform the ray into the local space of the box, where it is an AABB with mins at -1 and maxs at 1
					float3 LocalRayStart		= mul(float4(WorldPosition, 1), ReflectionCapture.BoxTransform[CaptureIndex]).xyz;
					float3 LocalRayDirection	= mul(float4(RayDirection,  0), ReflectionCapture.BoxTransform[CaptureIndex]).xyz;

					float3 InvRayDir = rcp(LocalRayDirection);
	
					//find the ray intersection with each of the 3 planes defined by the minimum extrema.
					float3 FirstPlaneIntersections = -InvRayDir - LocalRayStart * InvRayDir;
					//find the ray intersection with each of the 3 planes defined by the maximum extrema.
					float3 SecondPlaneIntersections = InvRayDir - LocalRayStart * InvRayDir;
					//get the furthest of these intersections along the ray
					float3 FurthestPlaneIntersections = max(FirstPlaneIntersections, SecondPlaneIntersections);

					//clamp the intersections to be between RayOrigin and RayEnd on the ray
					float Intersection = min(FurthestPlaneIntersections.x, min(FurthestPlaneIntersections.y, FurthestPlaneIntersections.z));

					// Compute the reprojected vector
					float3 IntersectPosition = WorldPosition + Intersection * RayDirection;
					ProjectedCaptureVector = IntersectPosition - CapturePositionAndRadius.xyz;

					// Compute the distance from the receiving pixel to the box for masking
					// Apply local to world scale to take scale into account without transforming back to world space
					// Shrink the box by the transition distance (BoxScales.w) so that the fade happens inside the box influence area
					float4 BoxScales = ReflectionCapture.BoxScales[CaptureIndex];
					float BoxDistance = ComputeDistanceFromBoxToPoint(-(BoxScales.xyz - .5f * BoxScales.w), BoxScales.xyz - .5f * BoxScales.w, LocalRayStart * BoxScales.xyz);

					// Setup a fade based on receiver distance to the box, hides the box influence shape
					DistanceAlpha = 1.0 - smoothstep(0, .7f * BoxScales.w, BoxDistance);
				}
				// Sphere
				else
				{
					float ProjectionSphereRadius = CapturePositionAndRadius.w * 1.2f;
					float SphereRadiusSquared = ProjectionSphereRadius * ProjectionSphereRadius;

					float3 ReceiverToSphereCenter = WorldPosition - CapturePositionAndRadius.xyz;
					float ReceiverToSphereCenterSq = dot(ReceiverToSphereCenter, ReceiverToSphereCenter);

					// Find the intersection between the ray along the reflection vector and the capture's sphere
					float3 QuadraticCoef;
					QuadraticCoef.x = 1;
					QuadraticCoef.y = 2 * dot(RayDirection, ReceiverToSphereCenter);
					QuadraticCoef.z = ReceiverToSphereCenterSq - SphereRadiusSquared;

					float Determinant = QuadraticCoef.y * QuadraticCoef.y - 4 * QuadraticCoef.z;
							 
					// Only continue if the ray intersects the sphere
					if (Determinant >= 0)
					{
						float FarIntersection = (sqrt(Determinant) - QuadraticCoef.y) * 0.5;

						float3 IntersectPosition = WorldPosition + FarIntersection * RayDirection;
						ProjectedCaptureVector = IntersectPosition - CapturePositionAndRadius.xyz;
						// Note: some compilers don't handle smoothstep min > max (this was 1, .6)
						DistanceAlpha = 1.0 - smoothstep(.6, 1, NormalizedDistanceToCapture);
					}
				}

			#else 
				DistanceAlpha = 1.0;
			#endif

			float CaptureArrayIndex = CaptureProperties.g;
			float Opacity = 0;

			UNROLL
			for( uint Lobe = 0; Lobe < NumLobes; Lobe++ )
			{
				float3 SampleDir = lerp( Lobes[ Lobe ].Direction, ProjectedCaptureVector, Lobes[ Lobe ].RayInfluance );
				float4 Sample = ReflectionEnvironmentColorTexture.SampleLevel( ReflectionEnvironmentColorSampler, float4( SampleDir, CaptureArrayIndex ), LobeMip[ Lobe ] );

				Sample.rgb *= CaptureProperties.r;
				Sample *= DistanceAlpha;

				// Under operator (back to front)
				Lobes[ Lobe ].Color.rgb += Sample.rgb * Lobes[ Lobe ].Color.a;
				Lobes[ Lobe ].Color.a *= 1 - Sample.a;

				Opacity += Lobes[ Lobe ].Color.a;
			}

			BRANCH
			if( Opacity < 0.001 )
			{
				break;
			}
		}
	}

#define APPLY_SKY_LIGHT 1
#if APPLY_SKY_LIGHT
	float Opacity = 0;

	UNROLL
	for( uint Lobe = 0; Lobe < NumLobes; Lobe++ )
	{
		Opacity += Lobes[ Lobe ].Color.a;
	}

	BRANCH
	if( SkyLightParameters.y > 0 && Opacity >= 0.001 )
	{
		UNROLL
		for( uint Lobe = 0; Lobe < NumLobes; Lobe++ )
		{
			// TODO use LobeMip
			Lobes[ Lobe ].Color.rgb += Lobes[ Lobe ].Color.a * GetSkyLightReflection( Lobes[ Lobe ].Direction, Lobes[ Lobe ].Roughness, USE_LIGHTMAPS );
		}
	}
#endif
}


float CountOverlap( float3 WorldPosition )
{
	float Overlap = 0;
	float Opacity = 1;

	uint NumCapturesAffectingTile = TileNumReflectionCaptures;

	// Accumulate reflections from captures affecting this tile, applying largest captures first so that the smallest ones display on top
	LOOP
	for (uint TileCaptureIndex = 0; TileCaptureIndex < NumCapturesAffectingTile; TileCaptureIndex++) 
	{
		#if SORT_CAPTURES
			uint CaptureIndex = SortedTileReflectionCaptureIndices[TileCaptureIndex];
		#else
			uint CaptureIndex = TileReflectionCaptureIndices[TileCaptureIndex];
		#endif
			
		float4 CapturePositionAndRadius = ReflectionCapture.PositionAndRadius[CaptureIndex];
		float3 CaptureVector = WorldPosition - CapturePositionAndRadius.xyz;
		float CaptureVectorLength = sqrt(dot(CaptureVector, CaptureVector));

		BRANCH
		if (CaptureVectorLength < CapturePositionAndRadius.w)
		{
			float NormalizedDistanceToCapture = saturate(CaptureVectorLength / CapturePositionAndRadius.w);

			// Fade out based on distance to capture
			float DistanceAlpha = 1.0 - smoothstep(.6, 1, NormalizedDistanceToCapture);

			Overlap += 1;
			Opacity *= 1 - DistanceAlpha;

			BRANCH
			if( Opacity < 0.001 )
			{
				break;
			}
		}
	}

	return Overlap;
}


Texture2D ScreenSpaceReflections;
Texture2D InSceneColor;

/** Output HDR target. */
RWTexture2D<float4> RWOutSceneColor;

[numthreads(THREADGROUP_SIZEX, THREADGROUP_SIZEY, 1)]
void ReflectionEnvironmentTiledDeferredMain(
	uint3 GroupId : SV_GroupID,
	uint3 DispatchThreadId : SV_DispatchThreadID,
	uint3 GroupThreadId : SV_GroupThreadID) 
{
	uint ThreadIndex = GroupThreadId.y * THREADGROUP_SIZEX + GroupThreadId.x;
	
	uint2 PixelPos = DispatchThreadId.xy + ViewDimensions.xy;
	float2 ScreenUV = (float2(DispatchThreadId.xy) + .5f) / (ViewDimensions.zw - ViewDimensions.xy);
	float2 ScreenPosition = float2(2.0f, -2.0f) * ScreenUV + float2(-1.0f, 1.0f);
	float SceneDepth = CalcSceneDepth(PixelPos);

	float MinTileZ;
	float MaxTileZ;
	float MinTileZ2;
	float MaxTileZ2;
	ComputeTileMinMax(ThreadIndex, SceneDepth, MinTileZ, MaxTileZ, MinTileZ2, MaxTileZ2);

	DoTileCulling(GroupId, ThreadIndex, MinTileZ, MaxTileZ, MinTileZ2, MaxTileZ2);

	// Lookup GBuffer properties once per pixel
	FScreenSpaceData ScreenSpaceData = GetScreenSpaceDataUint(PixelPos);
	FGBufferData GBuffer = ScreenSpaceData.GBuffer;
	
	float4 HomogeneousWorldPosition = mul(float4(ScreenPosition * SceneDepth, SceneDepth, 1), View.ScreenToWorld);
	float3 WorldPosition = HomogeneousWorldPosition.xyz / HomogeneousWorldPosition.w;
	float3 CameraToPixel = normalize(WorldPosition - View.ViewOrigin.xyz);
	float3 ReflectionVector = reflect(CameraToPixel, GBuffer.WorldNormal);
	
	// Save GPRs by using R instead of V
	float NoV = saturate( dot( GBuffer.WorldNormal, ReflectionVector ) );

	FLobe Lobes[2];

	UNROLL
	for( uint Lobe = 0; Lobe < 2; Lobe++ )
	{
		Lobes[ Lobe ].Color			= float4(0, 0, 0, 1);
		Lobes[ Lobe ].Direction		= ReflectionVector;
		Lobes[ Lobe ].RayInfluance	= 1;
		Lobes[ Lobe ].Roughness		= GBuffer.Roughness;
	}

#if VISUALIZE_OVERLAP
	float Overlap = CountOverlap( WorldPosition );
#else

#if 1//APPLY_SSR
	float4 SSR = ScreenSpaceReflections.Load( int3(PixelPos, 0) );
	Lobes[0].Color.rgb = SSR.rgb;
	Lobes[0].Color.a = 1 - SSR.a;
#endif

#if USE_LIGHTMAPS
	// We have high frequency directional data but low frequency spatial data in the envmap.
	// We have high frequency spatial data but low frequency directional data in the lightmap.
	// So, we combine the two for the best of both. This is done by removing the low spatial frequencies from the envmap and replacing them with the lightmap data.
	// This is only done with luma so as to not get odd color shifting.
	// Note: make sure this matches the lightmap mixing done for translucency (BasePassPixelShader.usf)
	Lobes[0].Color.a *= GBuffer.IndirectIrradiance;
	Lobes[1].Color.a *= GBuffer.IndirectIrradiance;
#else
	// Diffuse lobe
	Lobes[1].Direction		= GBuffer.WorldNormal;
	Lobes[1].RayInfluance	= 0;
	Lobes[1].Roughness		= 1;
#endif
	
	float AO = ScreenSpaceData.AmbientOcclusion;
	float SpecularOcclusion = saturate( Square( NoV + AO ) - 1 + AO );

	Lobes[0].Color.a *= SpecularOcclusion;
	Lobes[1].Color.a *= AO;

	BRANCH	//[forcecase]
	switch( GBuffer.ShadingModelID )
	{
		case SHADINGMODELID_UNLIT:
			break;
		case SHADINGMODELID_DEFAULT_LIT:
		case SHADINGMODELID_SUBSURFACE:
		case SHADINGMODELID_PREINTEGRATED_SKIN:
		case SHADINGMODELID_SUBSURFACE_PROFILE:
		{
			BRANCH
			if( GBuffer.ShadingModelID == SHADINGMODELID_SUBSURFACE )
			{
				GBuffer.DiffuseColor += ExtractSubsurfaceColor(GBuffer);
			}

		#if USE_LIGHTMAPS
			GBuffer.DiffuseColor = 0;
		#endif

			GBuffer.SpecularColor = EnvBRDF( GBuffer.SpecularColor, GBuffer.Roughness, NoV );

			GatherRadiance( Lobes, USE_LIGHTMAPS ? 1 : 2, WorldPosition, ReflectionVector );

			Lobes[0].Color.rgb *= GBuffer.SpecularColor;
			Lobes[1].Color.rgb *= GBuffer.DiffuseColor;
			break;
		}
		case SHADINGMODELID_CLEAR_COAT:
#if 1
		{
			const float ClearCoat			= GBuffer.CustomData.x;
			const float ClearCoatRoughness	= GBuffer.CustomData.y;

		#if USE_LIGHTMAPS
			Lobes[0].Roughness = ClearCoatRoughness;
		#else
			Lobes[0].Roughness = lerp( GBuffer.Roughness, ClearCoatRoughness, ClearCoat );
			Lobes[1].Roughness = lerp( 1, GBuffer.Roughness, GBuffer.Metallic * ClearCoat );
			Lobes[1].Direction = lerp( GBuffer.WorldNormal, ReflectionVector, ClearCoat );
			Lobes[1].RayInfluance = ClearCoat;
		#endif

			// TODO EnvBRDF should have a mask param
			float2 AB = PreIntegratedGF.SampleLevel( PreIntegratedGFSampler, float2( NoV, GBuffer.Roughness ), 0 ).rg;
			GBuffer.SpecularColor = GBuffer.SpecularColor * AB.x + AB.y * saturate( 50 * GBuffer.SpecularColor.g ) * (1 - ClearCoat);
			
			// F_Schlick
			float F0 = 0.04;
			float Fc = pow( 1 - NoV, 5 );
			float F = Fc + (1 - Fc) * F0;
			F *= ClearCoat;
			
			float LayerAttenuation = (1 - F);

		#if USE_LIGHTMAPS
			Lobes[0].Color.a *= F;
			Lobes[1].Color.a *= LayerAttenuation;

			float3 Lobe0Reflectance = 1;
			float3 Lobe1Reflectance = GBuffer.SpecularColor;
		#else
			float3 Lobe0Reflectance = lerp( GBuffer.SpecularColor, F, ClearCoat );
			float3 Lobe1Reflectance = ( GBuffer.DiffuseColor + GBuffer.SpecularColor * ClearCoat ) * LayerAttenuation;
		#endif

			GatherRadiance( Lobes, 2, WorldPosition, ReflectionVector );
			
			Lobes[0].Color.rgb *= Lobe0Reflectance;
			Lobes[1].Color.rgb *= Lobe1Reflectance;
			break;
		}
#endif
		default:
			break;
	}
#endif

	// Only write to the buffer for threads inside the view
	BRANCH
	if (all(DispatchThreadId.xy < ViewDimensions.zw)) 
	{
		float4 OutColor = 0;

#if VISUALIZE_OVERLAP
		//OutColor.rgb = 0.1 * TileNumReflectionCaptures;
		OutColor.rgb = 0.1 * Overlap;
#else
		OutColor.rgb += Lobes[0].Color.rgb;
		OutColor.rgb += Lobes[1].Color.rgb;
#endif

		// Transform NaNs to black, transform negative colors to black.
		OutColor.rgb = -min(-OutColor.rgb, 0.0);

		// alpha channel is also added to keep the alpha channel for screen space subsurface scattering
		OutColor += InSceneColor.Load( int3(PixelPos, 0) );

		RWOutSceneColor[PixelPos.xy] = OutColor;
	}
}

#endif