InstanceCullingManager.h

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// Copyright Epic Games, Inc. All Rights Reserved.
 
#pragma once
 
#include "InstanceCulling/InstanceCullingContext.h"
#include "InstanceCullingLoadBalancer.h"
#include "RenderGraphResources.h"
#include "Async/Mutex.h"
#include "SceneUniformBuffer.h"
 
class FRendererViewDataManager;
 
class FGPUScene;
 
namespace Nanite
{
    struct FPackedView;
    struct FPackedViewParams;
}
 
class FInstanceProcessingGPULoadBalancer : public TInstanceCullingLoadBalancer<>
{
public:
};
 
struct FInstanceCullingResult
{
    FInstanceCullingDrawParams Parameters;
 
    inline void GetDrawParameters(FInstanceCullingDrawParams &OutParams) const
    {
        OutParams = Parameters;
    }
};
 
class FInstanceCullingDeferredContext;
 
class FInstanceCullingManager
{
public:
    FInstanceCullingManager(FRDGBuilder& GraphBuilder, const FScene& InScene, FSceneUniformBuffer& InSceneUniforms, FRendererViewDataManager& InViewDataManager);
 
    ~FInstanceCullingManager();
 
    bool IsEnabled() const { return bIsEnabled; }
 
    // Register a non-primary view for culling, returns integer ID of the view.
    int32 RegisterView(const Nanite::FPackedViewParams& Params);
 
    // Allocate space for views ahead of time prior to calling RegisterView.
    void AllocateViews(int32 NumViews);
 
    const TRDGUniformBufferRef<FInstanceCullingGlobalUniforms> GetDummyInstanceCullingUniformBuffer() const { return DummyUniformBuffer; }
    
    static bool AllowBatchedBuildRenderingCommands(const FGPUScene& GPUScene);
 
    void BeginDeferredCulling(FRDGBuilder& GraphBuilder);
 
 
    bool IsDeferredCullingActive() const { return DeferredContext != nullptr; }
 
    // Reference to a buffer owned by FInstanceCullingOcclusionQueryRenderer
    FRDGBufferRef InstanceOcclusionQueryBuffer = {};
    EPixelFormat InstanceOcclusionQueryBufferFormat = PF_Unknown;
 
    TArray<TRefCountPtr<IPooledRenderTarget>> ViewPrevHZBs;
 
    // to support merging of multiple contexts with different HZBs, we use separate bins (LoadBalancers) in the InstanceCullingDeferredContext
    // bin 0 is reserved for UnCulled batches. Bins >= 1 are for the different HZBs.
    int32 GetBinIndex(EBatchProcessingMode Mode, const TRefCountPtr<IPooledRenderTarget>& HZB);
 
    void SetDummyCullingParams(FRDGBuilder& GraphBuilder, FInstanceCullingDrawParams& Parameters);
 
private:
    friend class FInstanceCullingContext;
    
    // Polulated by FInstanceCullingContext::BuildRenderingCommandsDeferred, used to hold instance culling related data that needs to be passed around
    FInstanceCullingDeferredContext* DeferredContext = nullptr;
 
    FInstanceCullingManager() = delete;
    FInstanceCullingManager(FInstanceCullingManager &) = delete;
 
    const FScene& Scene;
    const FGPUScene& GPUScene;
    FSceneUniformBuffer& SceneUniforms;
    FRendererViewDataManager& ViewDataManager;
 
    bool bIsEnabled;
 
    TRDGUniformBufferRef<FInstanceCullingGlobalUniforms> DummyUniformBuffer;
};