// Copyright Epic Games, Inc. All Rights Reserved.

/*=============================================================================
	VirtualShadowMap.h:
=============================================================================*/
#include "VirtualShadowMapCacheManager.h"
#include "RendererModule.h"
#include "RenderGraphUtils.h"
#include "RHIGPUReadback.h"
#include "ScenePrivate.h"
#include "HAL/FileManager.h"

#include "PrimitiveSceneInfo.h"

static TAutoConsoleVariable<int32> CVarAccumulateStats(
	TEXT("r.Shadow.Virtual.AccumulateStats"),
	0,
	TEXT("AccumulateStats"),
	ECVF_RenderThreadSafe
);

static TAutoConsoleVariable<int32> CVarCacheVirtualSMs(
	TEXT("r.Shadow.Virtual.Cache"),
	1,
	TEXT("Turn on to enable caching"),
	ECVF_RenderThreadSafe
);


void FVirtualShadowMapCacheEntry::UpdateClipmap(
	int32 VirtualShadowMapId,
	const FMatrix &WorldToLight,
	FIntPoint PageSpaceLocation,
	float LevelRadius,
	float ViewCenterZ,
	float ViewRadiusZ)
{
	bool bCacheValid = (CurrentVirtualShadowMapId != INDEX_NONE);
	
	if (bCacheValid && WorldToLight != Clipmap.WorldToLight)
	{
		bCacheValid = false;
		//UE_LOG(LogRenderer, Display, TEXT("Invalidated clipmap level (VSM %d) due to light movement"), VirtualShadowMapId);
	}

#if 0
	// Disable cache panning for directional lights (debug)
	if (bCacheValid)
	{
		bCacheValid = bCacheValid && PageSpaceLocation.X == PrevPageSpaceLocation.X;
		bCacheValid = bCacheValid && PageSpaceLocation.Y == PrevPageSpaceLocation.Y;
		if (!bCacheValid)
		{
			//UE_LOG(LogRenderer, Display, TEXT("Invalidated clipmap level (VSM %d) with page space location %d,%d (Prev %d, %d)"),
			//	VirtualShadowMapId, PageSpaceLocation.X, PageSpaceLocation.Y, PrevPageSpaceLocation.X, PrevPageSpaceLocation.Y);
		}
	}
#endif

	// Invalidate if the new Z radius strayed too close/outside the guardband of the cached shadow map
	if (bCacheValid)
	{
		float DeltaZ = FMath::Abs(ViewCenterZ - Clipmap.ViewCenterZ);
		if ((DeltaZ + LevelRadius) > 0.9f * Clipmap.ViewRadiusZ)
		{
			bCacheValid = false;
			//UE_LOG(LogRenderer, Display, TEXT("Invalidated clipmap level (VSM %d) due to depth range movement"), VirtualShadowMapId);
		}
	}

	if (bCacheValid)
	{
		PrevVirtualShadowMapId = CurrentVirtualShadowMapId;
	}
	else
	{
		// New cached level
		PrevVirtualShadowMapId = INDEX_NONE;
		Clipmap.WorldToLight = WorldToLight;
		Clipmap.ViewCenterZ = ViewCenterZ;
		Clipmap.ViewRadiusZ = ViewRadiusZ;
	}
		
	PrevPageSpaceLocation = CurrentPageSpaceLocation;
	
	CurrentVirtualShadowMapId = VirtualShadowMapId;
	CurrentPageSpaceLocation = PageSpaceLocation;
}

void FVirtualShadowMapCacheEntry::UpdateLocal(int32 VirtualShadowMapId, const FWholeSceneProjectedShadowInitializer &InCacheValidKey)
{
	// Swap previous frame data over.
	PrevPageSpaceLocation = CurrentPageSpaceLocation;
	PrevVirtualShadowMapId = CurrentVirtualShadowMapId;

	// Check cache validity based of shadow setup
	if (!LocalCacheValidKey.IsCachedShadowValid(InCacheValidKey))
	{
		PrevVirtualShadowMapId = INDEX_NONE;
		//UE_LOG(LogRenderer, Display, TEXT("Invalidated!"));
	}
	LocalCacheValidKey = InCacheValidKey;

	CurrentVirtualShadowMapId = VirtualShadowMapId;
	PrevPageSpaceLocation = CurrentPageSpaceLocation = FIntPoint(0, 0);
}


TSharedPtr<FVirtualShadowMapCacheEntry> FVirtualShadowMapArrayCacheManager::FindCreateCacheEntry(int32 LightSceneId, int32 CascadeIndex)
{
	if (CVarCacheVirtualSMs.GetValueOnRenderThread() == 0)
	{
		return nullptr;
	}

	const FIntPoint Key(LightSceneId, CascadeIndex);

	if (TSharedPtr<FVirtualShadowMapCacheEntry> *VirtualShadowMapCacheEntry = CacheEntries.Find(Key))
	{
		return *VirtualShadowMapCacheEntry;
	}

	// Add to current frame / active set.
	TSharedPtr<FVirtualShadowMapCacheEntry> &NewVirtualShadowMapCacheEntry = CacheEntries.Add(Key);

	// Copy data if available
	if (TSharedPtr<FVirtualShadowMapCacheEntry> *PrevVirtualShadowMapCacheEntry = PrevCacheEntries.Find(Key))
	{
		NewVirtualShadowMapCacheEntry = *PrevVirtualShadowMapCacheEntry;
	}
	else
	{
		NewVirtualShadowMapCacheEntry = TSharedPtr<FVirtualShadowMapCacheEntry>(new FVirtualShadowMapCacheEntry);
	}

	// return entry
	return NewVirtualShadowMapCacheEntry;
}


class FVirtualSmCopyStatsCS : public FGlobalShader
{
	DECLARE_GLOBAL_SHADER(FVirtualSmCopyStatsCS);
	SHADER_USE_PARAMETER_STRUCT(FVirtualSmCopyStatsCS, FGlobalShader)
public:
	BEGIN_SHADER_PARAMETER_STRUCT(FParameters, )
		SHADER_PARAMETER_RDG_BUFFER_SRV(StructuredBuffer< uint >, InStatsBuffer)
		SHADER_PARAMETER_RDG_BUFFER_UAV(RWBuffer< uint >, AccumulatedStatsBufferOut)
		SHADER_PARAMETER(uint32, NumStats)
	END_SHADER_PARAMETER_STRUCT()
	
	static bool ShouldCompilePermutation(const FGlobalShaderPermutationParameters& Parameters)
	{
		return IsFeatureLevelSupported(Parameters.Platform, ERHIFeatureLevel::SM5);
	}

	static void ModifyCompilationEnvironment(const FGlobalShaderPermutationParameters& Parameters, FShaderCompilerEnvironment& OutEnvironment)
	{
		FGlobalShader::ModifyCompilationEnvironment(Parameters, OutEnvironment);

		OutEnvironment.SetDefine(TEXT("MAX_STAT_FRAMES"), FVirtualShadowMapArrayCacheManager::MaxStatFrames);
	}
};
IMPLEMENT_GLOBAL_SHADER(FVirtualSmCopyStatsCS, "/Engine/Private/VirtualShadowMaps/CopyStats.usf", "CopyStatsCS", SF_Compute);

void FVirtualShadowMapArrayCacheManager::ExtractFrameData(bool bEnableCaching, FVirtualShadowMapArray &VirtualShadowMapArray, FRDGBuilder& GraphBuilder)
{
	// Drop all refs.
	PrevBuffers = FVirtualShadowMapArrayFrameData();
	PrevUniformParameters.NumShadowMaps = 0;

	if (bEnableCaching && VirtualShadowMapArray.IsAllocated())
	{
		bool bExtractPageTable = false;

		// HZB and associated page table are needed by next frame even when VSM physical page caching is disabled
		if (VirtualShadowMapArray.HZBPhysical)
		{
			bExtractPageTable = true;
			GraphBuilder.QueueTextureExtraction(VirtualShadowMapArray.HZBPhysical, &PrevBuffers.HZBPhysical);
			PrevBuffers.HZBMetadata = VirtualShadowMapArray.HZBMetadata;
		}

		if (CVarCacheVirtualSMs.GetValueOnRenderThread() != 0)
		{
			bExtractPageTable = true;
			GraphBuilder.QueueBufferExtraction(VirtualShadowMapArray.PageFlagsRDG, &PrevBuffers.PageFlags);
			GraphBuilder.QueueBufferExtraction(VirtualShadowMapArray.HPageFlagsRDG, &PrevBuffers.HPageFlags);
		
			GraphBuilder.QueueTextureExtraction(VirtualShadowMapArray.PhysicalPagePoolRDG, &PrevBuffers.PhysicalPagePool);

			if( VirtualShadowMapArray.PhysicalPagePoolHw )
			{
				GraphBuilder.QueueTextureExtraction(VirtualShadowMapArray.PhysicalPagePoolHw, &PrevBuffers.PhysicalPagePoolHw);
			}
			else
			{
				PrevBuffers.PhysicalPagePoolHw = TRefCountPtr<IPooledRenderTarget>();
			}

			GraphBuilder.QueueBufferExtraction(VirtualShadowMapArray.PhysicalPageMetaDataRDG, &PrevBuffers.PhysicalPageMetaData);
			GraphBuilder.QueueBufferExtraction(VirtualShadowMapArray.DynamicCasterPageFlagsRDG, &PrevBuffers.DynamicCasterPageFlags);
			GraphBuilder.QueueBufferExtraction(VirtualShadowMapArray.ShadowMapProjectionDataRDG, &PrevBuffers.ShadowMapProjectionDataBuffer);
			GraphBuilder.QueueBufferExtraction(VirtualShadowMapArray.PageRectBoundsRDG, &PrevBuffers.PageRectBounds);
			// Move cache entries to previous frame, this implicitly removes any that were not used
			PrevCacheEntries = CacheEntries;
			PrevUniformParameters = VirtualShadowMapArray.UniformParameters;
		}

		if (bExtractPageTable)
		{
			GraphBuilder.QueueBufferExtraction(VirtualShadowMapArray.PageTableRDG, &PrevBuffers.PageTable);
		}
	}
	else
	{
		PrevCacheEntries.Empty();
	}
	CacheEntries.Reset();

	// Drop any references embedded in the uniform parameters this frame.
	// We'll reestablish them when we reimport the extracted resources next frame
	PrevUniformParameters.ProjectionData = nullptr;
	PrevUniformParameters.PageTable = nullptr;
	PrevUniformParameters.PhysicalPagePool = nullptr;
	PrevUniformParameters.PhysicalPagePoolHw = nullptr;

	FRDGBufferRef AccumulatedStatsBufferRDG = nullptr;

	// Note: stats accumulation thing is here because it needs to persist over frames.
	if (!AccumulatedStatsBuffer.IsValid())
	{
		AccumulatedStatsBufferRDG = GraphBuilder.CreateBuffer(FRDGBufferDesc::CreateBufferDesc(4, 1 + FVirtualShadowMapArray::NumStats * MaxStatFrames), TEXT("Shadow.Virtual.AccumulatedStatsBuffer"));	// TODO: Can't be a structured buffer as EnqueueCopy is only defined for vertex buffers
		AddClearUAVPass(GraphBuilder, GraphBuilder.CreateUAV(AccumulatedStatsBufferRDG, PF_R32_UINT), 0);
		AccumulatedStatsBuffer = GraphBuilder.ConvertToExternalBuffer(AccumulatedStatsBufferRDG);
	}
	else
	{
		AccumulatedStatsBufferRDG = GraphBuilder.RegisterExternalBuffer(AccumulatedStatsBuffer, TEXT("Shadow.Virtual.AccumulatedStatsBuffer"));
	}

	if (IsAccumulatingStats())
	{
		// Initialize/clear
		if (!bAccumulatingStats)
		{
			AddClearUAVPass(GraphBuilder, GraphBuilder.CreateUAV(AccumulatedStatsBufferRDG, PF_R32_UINT), 0);
			bAccumulatingStats = true;
		}

		FVirtualSmCopyStatsCS::FParameters* PassParameters = GraphBuilder.AllocParameters<FVirtualSmCopyStatsCS::FParameters>();

		PassParameters->InStatsBuffer = GraphBuilder.CreateSRV(VirtualShadowMapArray.StatsBufferRDG, PF_R32_UINT);
		PassParameters->AccumulatedStatsBufferOut = GraphBuilder.CreateUAV(AccumulatedStatsBufferRDG, PF_R32_UINT);
		PassParameters->NumStats = FVirtualShadowMapArray::NumStats;

		auto ComputeShader = GetGlobalShaderMap(GMaxRHIFeatureLevel)->GetShader<FVirtualSmCopyStatsCS>();

		FComputeShaderUtils::AddPass(
			GraphBuilder,
			RDG_EVENT_NAME("Copy Stats"),
			ComputeShader,
			PassParameters,
			FIntVector(1, 1, 1)
		);
	}
	else if (bAccumulatingStats)
	{
		bAccumulatingStats = false;

		GPUBufferReadback = new FRHIGPUBufferReadback(TEXT("Shadow.Virtual.AccumulatedStatsBuffer"));
		AddEnqueueCopyPass(GraphBuilder, GPUBufferReadback, AccumulatedStatsBufferRDG, 0u);
	}

	if (GPUBufferReadback && GPUBufferReadback->IsReady())
	{
		TArray<uint32> Tmp;
		Tmp.AddDefaulted(1 + FVirtualShadowMapArray::NumStats * MaxStatFrames);

		{
			const uint32* BufferPtr = (const uint32*)GPUBufferReadback->Lock((1 + FVirtualShadowMapArray::NumStats * MaxStatFrames) * sizeof(uint32));
			FPlatformMemory::Memcpy(Tmp.GetData(), BufferPtr, Tmp.Num() * Tmp.GetTypeSize());
			GPUBufferReadback->Unlock();

			delete GPUBufferReadback;
			GPUBufferReadback = nullptr;
		}

		FString FileName = TEXT("VirtualShadowMapCacheStats.csv");// FString::Printf(TEXT("%s.csv"), *FileNameToUse);
		FArchive * FileToLogTo = IFileManager::Get().CreateFileWriter(*FileName, false);
		ensure(FileToLogTo);
		if (FileToLogTo)
		{
			static const FString StatNames[FVirtualShadowMapArray::NumStats] =
			{
				TEXT("Allocated"),
				TEXT("Cached"),
				TEXT("Dynamic"),
				TEXT("NumSms"),
				TEXT("RandRobin"),
			};


			// Print header
			FString StringToPrint;
			for (const FString &StatName : StatNames)
			{
				if (!StringToPrint.IsEmpty())
				{
					StringToPrint += TEXT(",");
				}

				StringToPrint += StatName;
			}

			StringToPrint += TEXT("\n");
			FileToLogTo->Serialize(TCHAR_TO_ANSI(*StringToPrint), StringToPrint.Len());

			uint32 Num = Tmp[0];
			for (uint32 Ind = 0; Ind < Num; ++Ind)
			{
				StringToPrint.Empty();

				for (uint32 StatInd = 0; StatInd < FVirtualShadowMapArray::NumStats; ++StatInd)
				{
					if (!StringToPrint.IsEmpty())
					{
						StringToPrint += TEXT(",");
					}

					StringToPrint += FString::Printf(TEXT("%d"), Tmp[1 + Ind * FVirtualShadowMapArray::NumStats + StatInd]);
				}

				StringToPrint += TEXT("\n");
				FileToLogTo->Serialize(TCHAR_TO_ANSI(*StringToPrint), StringToPrint.Len());
			}


			FileToLogTo->Close();
		}
	}
}

bool FVirtualShadowMapArrayCacheManager::IsValid()
{
	return CVarCacheVirtualSMs.GetValueOnRenderThread() != 0
		&& PrevBuffers.PageTable
		&& PrevBuffers.PageFlags
		&& (PrevBuffers.PhysicalPagePool || PrevBuffers.PhysicalPagePoolHw)
		&& PrevBuffers.PhysicalPageMetaData
		&& PrevBuffers.DynamicCasterPageFlags;
}


bool FVirtualShadowMapArrayCacheManager::IsAccumulatingStats()
{
	return CVarAccumulateStats.GetValueOnRenderThread() != 0;
}

void FVirtualShadowMapArrayCacheManager::ProcessRemovedPrimives(FRDGBuilder& GraphBuilder, const FGPUScene& GPUScene, const TArray<FPrimitiveSceneInfo*>& RemovedPrimitiveSceneInfos)
{
	if (CVarCacheVirtualSMs.GetValueOnRenderThread() != 0 && RemovedPrimitiveSceneInfos.Num() > 0 && PrevBuffers.DynamicCasterPageFlags.IsValid())
	{
		TArray<FInstanceSceneDataRange, SceneRenderingAllocator> InstanceRangesLarge;
		TArray<FInstanceSceneDataRange, SceneRenderingAllocator> InstanceRangesSmall;

		for (const FPrimitiveSceneInfo* PrimitiveSceneInfo : RemovedPrimitiveSceneInfos)
		{
			if (PrimitiveSceneInfo->GetInstanceSceneDataOffset() != INDEX_NONE)
			{
				const int32 NumInstanceSceneDataEntries = PrimitiveSceneInfo->GetNumInstanceSceneDataEntries();
				if (NumInstanceSceneDataEntries >= 8u)
				{
					InstanceRangesLarge.Add(FInstanceSceneDataRange{ PrimitiveSceneInfo->GetInstanceSceneDataOffset(), NumInstanceSceneDataEntries });
				}
				else
				{
					InstanceRangesSmall.Add(FInstanceSceneDataRange{ PrimitiveSceneInfo->GetInstanceSceneDataOffset(), NumInstanceSceneDataEntries });
				}
			}
		}
		ProcessInstanceRangeInvalidation(GraphBuilder, InstanceRangesLarge, InstanceRangesSmall, GPUScene);
	}
}


void FVirtualShadowMapArrayCacheManager::ProcessPrimitivesToUpdate(FRDGBuilder& GraphBuilder, const FScene &Scene)
{
	const FGPUScene& GPUScene = Scene.GPUScene;
	if (IsValid() && GPUScene.PrimitivesToUpdate.Num() > 0)
	{
		// TODO: As a slight CPU optimization just pass primitive ID list and use instance ranges stored in GPU scene
		TArray<FInstanceSceneDataRange, SceneRenderingAllocator> InstanceRangesLarge;
		TArray<FInstanceSceneDataRange, SceneRenderingAllocator> InstanceRangesSmall;

		for (const int32 PrimitiveId : GPUScene.PrimitivesToUpdate)
		{
			// There may possibly be IDs that are out of range if they were marked for update and then removed.
			if (PrimitiveId < Scene.Primitives.Num())
			{
				EPrimitiveDirtyState PrimitiveDirtyState = GPUScene.GetPrimitiveDirtyState(PrimitiveId);

				// SKIP if marked for Add, because this means it has no previous location to invalidate.
				// SKIP if transform has not changed, as this means no invalidation needs to take place.
				if (!EnumHasAnyFlags(PrimitiveDirtyState, EPrimitiveDirtyState::Added) && EnumHasAnyFlags(PrimitiveDirtyState, EPrimitiveDirtyState::ChangedTransform))
				{
					const FPrimitiveSceneInfo* PrimitiveSceneInfo = Scene.Primitives[PrimitiveId];
					if (PrimitiveSceneInfo->GetInstanceSceneDataOffset() != INDEX_NONE)
					{
						int32 NumInstanceSceneDataEntries = PrimitiveSceneInfo->GetNumInstanceSceneDataEntries();
						if (NumInstanceSceneDataEntries >= 8u)
						{
							InstanceRangesLarge.Add(FInstanceSceneDataRange{ PrimitiveSceneInfo->GetInstanceSceneDataOffset(), NumInstanceSceneDataEntries });
						}
						else
						{
							InstanceRangesSmall.Add(FInstanceSceneDataRange{ PrimitiveSceneInfo->GetInstanceSceneDataOffset(), NumInstanceSceneDataEntries });
						}
					}
				}
			}
		}
		ProcessInstanceRangeInvalidation(GraphBuilder, InstanceRangesLarge, InstanceRangesSmall, GPUScene);
	}
}

/**
 * Compute shader to project and invalidate the rectangles of given instances.
 */
class FVirtualSmInvalidateInstancePagesCS : public FGlobalShader
{
	DECLARE_GLOBAL_SHADER(FVirtualSmInvalidateInstancePagesCS);
	SHADER_USE_PARAMETER_STRUCT(FVirtualSmInvalidateInstancePagesCS, FGlobalShader)

	class FLargeSmallDim : SHADER_PERMUTATION_BOOL("PROCESS_LARGE_INSTANCE_COUNT_RANGES");
	using FPermutationDomain = TShaderPermutationDomain<FLargeSmallDim>;

public:
	BEGIN_SHADER_PARAMETER_STRUCT(FParameters, )
		SHADER_PARAMETER_RDG_UNIFORM_BUFFER(FVirtualShadowMapUniformParameters, VirtualShadowMap)
		SHADER_PARAMETER_RDG_BUFFER_SRV(StructuredBuffer< FInstanceSceneDataRange >, InstanceSceneRanges)
		SHADER_PARAMETER(uint32, NumRemovedItems)
		SHADER_PARAMETER_RDG_BUFFER_SRV(StructuredBuffer< uint >, PageFlags)
		SHADER_PARAMETER_RDG_BUFFER_SRV(StructuredBuffer< uint >, HPageFlags)
		SHADER_PARAMETER_RDG_BUFFER_SRV(StructuredBuffer< uint4 >, PageRectBounds)
		SHADER_PARAMETER_RDG_BUFFER_UAV(RWStructuredBuffer< uint >, OutDynamicCasterFlags)

		SHADER_PARAMETER_SRV(StructuredBuffer<float4>, GPUSceneInstanceSceneData)
		SHADER_PARAMETER_SRV(StructuredBuffer<float4>, GPUScenePrimitiveSceneData)
		SHADER_PARAMETER(uint32, GPUSceneFrameNumber)
		SHADER_PARAMETER(uint32, InstanceSceneDataSOAStride)
	END_SHADER_PARAMETER_STRUCT()

	static constexpr int Cs1dGroupSizeX = 64;

	static bool ShouldCompilePermutation(const FGlobalShaderPermutationParameters& Parameters)
	{
		return IsFeatureLevelSupported(Parameters.Platform, ERHIFeatureLevel::SM5);
	}

	static void ModifyCompilationEnvironment(const FGlobalShaderPermutationParameters& Parameters, FShaderCompilerEnvironment& OutEnvironment)
	{
		FGlobalShader::ModifyCompilationEnvironment(Parameters, OutEnvironment);
		FVirtualShadowMapArray::SetShaderDefines(OutEnvironment);
		OutEnvironment.SetDefine(TEXT("CS_1D_GROUP_SIZE_X"), Cs1dGroupSizeX);
		OutEnvironment.SetDefine(TEXT("USE_GLOBAL_GPU_SCENE_DATA"), 1);
		OutEnvironment.SetDefine(TEXT("VF_SUPPORTS_PRIMITIVE_SCENE_DATA"), 1);

		// OutEnvironment.SetDefine(TEXT("MAX_STAT_FRAMES"), FVirtualShadowMapArrayCacheManager::MaxStatFrames);
	}
};
IMPLEMENT_GLOBAL_SHADER(FVirtualSmInvalidateInstancePagesCS, "/Engine/Private/VirtualShadowMaps/CacheManagement.usf", "VirtualSmInvalidateInstancePagesCS", SF_Compute);


TRDGUniformBufferRef<FVirtualShadowMapUniformParameters> FVirtualShadowMapArrayCacheManager::GetPreviousUniformBuffer(FRDGBuilder& GraphBuilder) const
{
	FVirtualShadowMapUniformParameters* VersionedParameters = GraphBuilder.AllocParameters<FVirtualShadowMapUniformParameters>();
	*VersionedParameters = PrevUniformParameters;
	return GraphBuilder.CreateUniformBuffer(VersionedParameters);
}

void FVirtualShadowMapArrayCacheManager::ProcessInstanceRangeInvalidation(FRDGBuilder& GraphBuilder, const TArray<FInstanceSceneDataRange, SceneRenderingAllocator>& InstanceRangesLarge, const TArray<FInstanceSceneDataRange, SceneRenderingAllocator>& InstanceRangesSmall, const FGPUScene& GPUScene)
{
	auto RegExtCreateSrv = [&GraphBuilder](const TRefCountPtr<FRDGPooledBuffer>& Buffer, const TCHAR* Name) -> FRDGBufferSRVRef
	{
		return GraphBuilder.CreateSRV(GraphBuilder.RegisterExternalBuffer(Buffer, Name));
	};

	// Update references in our last frame uniform buffer with reimported resources for this frame
	PrevUniformParameters.ProjectionData = RegExtCreateSrv(PrevBuffers.ShadowMapProjectionDataBuffer, TEXT("Shadow.Virtual.PrevProjectionData"));
	PrevUniformParameters.PageTable = RegExtCreateSrv(PrevBuffers.PageTable, TEXT("Shadow.Virtual.PrevPageTable"));
	// Unused in this path
	PrevUniformParameters.PhysicalPagePool = GSystemTextures.GetZeroUIntDummy(GraphBuilder);
	PrevUniformParameters.PhysicalPagePoolHw = GSystemTextures.GetBlackDummy(GraphBuilder);

	FRDGBufferRef InstanceRangesSmallRDG = !InstanceRangesSmall.IsEmpty() ? CreateStructuredBuffer(GraphBuilder, TEXT("Shadow.Virtual.InstanceRangesSmall"), InstanceRangesSmall) : nullptr;
	FRDGBufferRef InstanceRangesLargeRDG = !InstanceRangesLarge.IsEmpty() ? CreateStructuredBuffer(GraphBuilder, TEXT("Shadow.Virtual.InstanceRangesSmall"), InstanceRangesLarge) : nullptr;

	if (InstanceRangesSmall.Num())
	{
		RDG_EVENT_SCOPE(GraphBuilder, "ProcessInstanceRangeInvalidation [%d small-ranges]", InstanceRangesSmall.Num());

		FVirtualSmInvalidateInstancePagesCS::FParameters* PassParameters = GraphBuilder.AllocParameters<FVirtualSmInvalidateInstancePagesCS::FParameters>();

		PassParameters->VirtualShadowMap = GetPreviousUniformBuffer(GraphBuilder);
		
		PassParameters->InstanceSceneRanges = GraphBuilder.CreateSRV(InstanceRangesSmallRDG);
		PassParameters->NumRemovedItems = InstanceRangesSmall.Num();

		PassParameters->PageFlags = RegExtCreateSrv(PrevBuffers.PageFlags, TEXT("Shadow.Virtual.PrevPageFlags"));
		PassParameters->HPageFlags = RegExtCreateSrv(PrevBuffers.HPageFlags, TEXT("Shadow.Virtual.PrevHPageFlags"));
		PassParameters->PageRectBounds = RegExtCreateSrv(PrevBuffers.PageRectBounds, TEXT("Shadow.Virtual.PrevPageRectBounds"));

		FRDGBufferRef DynamicCasterFlagsRDG = GraphBuilder.RegisterExternalBuffer(PrevBuffers.DynamicCasterPageFlags, TEXT("Shadow.Virtual.PrevDynamicCasterFlags"));
		PassParameters->OutDynamicCasterFlags = GraphBuilder.CreateUAV(DynamicCasterFlagsRDG);

		PassParameters->GPUSceneInstanceSceneData = GPUScene.InstanceSceneDataBuffer.SRV;
		PassParameters->GPUScenePrimitiveSceneData = GPUScene.PrimitiveBuffer.SRV;
		PassParameters->GPUSceneFrameNumber = GPUScene.GetSceneFrameNumber();
		PassParameters->InstanceSceneDataSOAStride = GPUScene.InstanceSceneDataSOAStride;

		FVirtualSmInvalidateInstancePagesCS::FPermutationDomain PermutationVector;
		PermutationVector.Set<FVirtualSmInvalidateInstancePagesCS::FLargeSmallDim>(0);

		auto ComputeShader = GetGlobalShaderMap(GMaxRHIFeatureLevel)->GetShader<FVirtualSmInvalidateInstancePagesCS>(PermutationVector);

		FComputeShaderUtils::AddPass(
			GraphBuilder,
			RDG_EVENT_NAME("VirtualSmInvalidateInstancePagesCS"),
			ComputeShader,
			PassParameters,
			FIntVector(FMath::DivideAndRoundUp(InstanceRangesSmall.Num(), FVirtualSmInvalidateInstancePagesCS::Cs1dGroupSizeX), 1, 1)
		);
	}
	if (InstanceRangesLarge.Num())
	{
		RDG_EVENT_SCOPE(GraphBuilder, "ProcessInstanceRangeInvalidation [%d large-ranges]", InstanceRangesLarge.Num());

		FVirtualSmInvalidateInstancePagesCS::FParameters* PassParameters = GraphBuilder.AllocParameters<FVirtualSmInvalidateInstancePagesCS::FParameters>();

		PassParameters->VirtualShadowMap = GetPreviousUniformBuffer(GraphBuilder);
		PassParameters->InstanceSceneRanges = GraphBuilder.CreateSRV(InstanceRangesLargeRDG);
		PassParameters->NumRemovedItems = InstanceRangesLarge.Num();

		PassParameters->PageFlags = RegExtCreateSrv(PrevBuffers.PageFlags, TEXT("Shadow.Virtual.PrevPageFlags"));
		PassParameters->HPageFlags = RegExtCreateSrv(PrevBuffers.HPageFlags, TEXT("Shadow.Virtual.PrevHPageFlags"));
		PassParameters->PageRectBounds = RegExtCreateSrv(PrevBuffers.PageRectBounds, TEXT("Shadow.Virtual.PrevPageRectBounds"));

		FRDGBufferRef DynamicCasterFlagsRDG = GraphBuilder.RegisterExternalBuffer(PrevBuffers.DynamicCasterPageFlags, TEXT("Shadow.Virtual.PrevDynamicCasterFlags"));
		PassParameters->OutDynamicCasterFlags = GraphBuilder.CreateUAV(DynamicCasterFlagsRDG);

		PassParameters->GPUSceneInstanceSceneData = GPUScene.InstanceSceneDataBuffer.SRV;
		PassParameters->GPUScenePrimitiveSceneData = GPUScene.PrimitiveBuffer.SRV;
		PassParameters->GPUSceneFrameNumber = GPUScene.GetSceneFrameNumber();
		PassParameters->InstanceSceneDataSOAStride = GPUScene.InstanceSceneDataSOAStride;

		FVirtualSmInvalidateInstancePagesCS::FPermutationDomain PermutationVector;
		PermutationVector.Set<FVirtualSmInvalidateInstancePagesCS::FLargeSmallDim>(1);

		auto ComputeShader = GetGlobalShaderMap(GMaxRHIFeatureLevel)->GetShader<FVirtualSmInvalidateInstancePagesCS>(PermutationVector);

		FComputeShaderUtils::AddPass(
			GraphBuilder,
			RDG_EVENT_NAME("VirtualSmInvalidateInstancePagesCS"),
			ComputeShader,
			PassParameters,
			FIntVector(InstanceRangesLarge.Num(), 1, 1)
		);
	}
}