InstanceCullingMergedContext.h

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// Copyright Epic Games, Inc. All Rights Reserved.
 
#pragma once
 
#include "CoreMinimal.h"
#include "InstanceCulling/InstanceCullingContext.h"
#include "InstanceCulling/InstanceCullingLoadBalancer.h"
 
class FInstanceCullingMergedContext
{
public:
    FInstanceCullingMergedContext(EShaderPlatform InShaderPlatform, bool bInMustAddAllContexts = false, int32 InNumBins = 2);
    
    struct FBatchItem
    {
        FInstanceCullingContext* Context = nullptr;
        FInstanceCullingDrawParams* Result = nullptr;
        // EBatchProcessingMode::Generic batches are put in bins, based on their view's PrevHZB
        int32 GenericBinIndex = -1;
    };
 
    // Info about a batch of culling work produced by a context, when part of a batched job
    // Store once per context, provides start offsets to commands/etc for the context.
    struct FContextBatchInfoPacked
    {
        uint32 IndirectArgsOffset;
        uint32 InstanceDataWriteOffset;
        uint32 PayloadDataOffset;
        uint32 CompactionDataOffset;
        uint32 ViewIdsOffset;
        uint32 NumViewIds_bAllowOcclusionCulling;
        uint32 DynamicInstanceIdOffset;
        uint32 DynamicInstanceIdMax;
        uint32 ItemDataOffset[uint32(EBatchProcessingMode::Num)];
    };
 
    static constexpr uint32 FirstGenericBinIndex = 1;
 
    TArray<FBatchItem, SceneRenderingAllocator> Batches;
 
    TArray<FBatchItem, SceneRenderingAllocator> AsyncBatches;
 
    TArray<int32, SceneRenderingAllocator> ViewIds;
    //TArray<FMeshDrawCommandInfo, SceneRenderingAllocator> MeshDrawCommandInfos;
    TArray<FRHIDrawIndexedIndirectParameters, SceneRenderingAllocator> IndirectArgs;
    TArray<FUintVector2, SceneRenderingAllocator> DrawCommandDescs;
    TArray<FInstanceCullingContext::FPayloadData, SceneRenderingAllocator> PayloadData;
    TArray<uint32, SceneRenderingAllocator> InstanceIdOffsets;
    TArray<FInstanceCullingContext::FCompactionData, SceneRenderingAllocator> DrawCommandCompactionData;
    TArray<uint32, SceneRenderingAllocator> CompactionBlockDataIndices; 
 
    // these are the actual BINS, so we would need one per HZB
    TArray<TInstanceCullingLoadBalancer<SceneRenderingAllocator>, SceneRenderingAllocator> LoadBalancers;
    TArray<TArray<uint32, SceneRenderingAllocator>, SceneRenderingAllocator> BatchInds; // TODO: rename to ContextInds
    TArray<FContextBatchInfoPacked, SceneRenderingAllocator> BatchInfos;
 
    EShaderPlatform ShaderPlatform = SP_NumPlatforms;
    // if true, the contexts that are supplied through calling AddBatch must all have an 1:1 entry in the resulting merged Batches array
    // this adds a check to prevent empty contexts from being added (!HasCullingCommands()).
    bool bMustAddAllContexts = false;
    // Counters to sum up all sizes to facilitate pre-sizing
    uint32 InstanceIdBufferElements = 0U;
    // preallocate 5 to cover all scenarios up to UnCulled bin + 4 HZBs in case of 4 primary views
    TArray<int32, TInlineAllocator<5>> TotalBatches;
    TArray<int32, TInlineAllocator<5>> TotalItems;
    int32 TotalIndirectArgs = 0;
    int32 TotalPayloads = 0;
    int32 TotalViewIds = 0;
    int32 TotalInstances = 0;
    int32 TotalCompactionDrawCommands = 0;
    int32 TotalCompactionBlocks = 0;
    int32 TotalCompactionInstances = 0;
 
    int32 NumCullingViews = 0;
 
    // Merge the queued batches and populate the derived data.
    void MergeBatches();
 
 
    void AddBatch(FRDGBuilder& GraphBuilder, FInstanceCullingContext* Context, FInstanceCullingDrawParams* InstanceCullingDrawParams);
 
private:
    void AddBatchItem(const FBatchItem& BatchItem);
 
    int32 GetLoadBalancerIndex(EBatchProcessingMode Mode, const FBatchItem& BatchItem);
 
};