NaniteVisibility.h

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// Copyright Epic Games, Inc. All Rights Reserved.
 
#pragma once
 
#include "NaniteShared.h"
//#include "NaniteCullRaster.h"
 
struct FNaniteVisibilityQuery;
 
class FNaniteVisibilityResults
{
    friend class FNaniteVisibility;
    friend struct FNaniteVisibilityQuery;
 
public:
    FNaniteVisibilityResults() = default;
 
    bool IsRasterBinVisible(uint16 BinIndex) const;
    bool IsShadingBinVisible(uint16 BinIndex) const;
 
    FORCEINLINE bool IsRasterTestValid() const
    {
        return bRasterTestValid;
    }
 
    FORCEINLINE bool IsShadingTestValid() const
    {
        return bShadingTestValid;
    }
 
    FORCEINLINE void GetRasterBinStats(uint32& OutNumVisible, uint32& OutNumTotal) const
    {
        OutNumTotal = TotalRasterBins;
        OutNumVisible = IsRasterTestValid() ? VisibleRasterBins : OutNumTotal;
    }
 
    FORCEINLINE void GetShadingBinStats(uint32& OutNumVisible, uint32& OutNumTotal) const
    {
        OutNumTotal = TotalShadingBins;
        OutNumVisible = IsShadingTestValid() ? VisibleShadingBins : OutNumTotal;
    }
 
    FORCEINLINE void SetRasterBinIndexTranslator(const FNaniteRasterBinIndexTranslator InTranslator)
    {
        BinIndexTranslator = InTranslator;
    }
 
    FORCEINLINE bool ShouldRenderCustomDepthPrimitive(uint32 PrimitiveId) const
    {
        if (!bRasterTestValid && !bShadingTestValid)
        {
            // no valid test results, so we didn't visibility test any primitives
            return true;
        }
        return VisibleCustomDepthPrimitives.Contains(PrimitiveId);
    }
 
    FORCEINLINE const TBitArray<>& GetRasterBinVisibility() const
    {
        return RasterBinVisibility;
    }
 
    FORCEINLINE const TBitArray<>& GetShadingBinVisibility() const
    {
        return ShadingBinVisibility;
    }
 
private:
    TBitArray<> RasterBinVisibility;
    TBitArray<> ShadingBinVisibility;
    TSet<uint32, DefaultKeyFuncs<uint32>, SceneRenderingSetAllocator> VisibleCustomDepthPrimitives;
    FNaniteRasterBinIndexTranslator BinIndexTranslator;
    uint32 TotalRasterBins      = 0;
    uint32 TotalShadingBins     = 0;
    uint32 VisibleRasterBins    = 0;
    uint32 VisibleShadingBins   = 0;
    bool bRasterTestValid       = false;
    bool bShadingTestValid      = false;
};
 
class FNaniteVisibility
{
    friend class FNaniteVisibilityTask;
 
public:
    struct FRasterBin
    {
        uint16 Primary = 0xFFFFu;
        uint16 Fallback = 0xFFFFu;
    };
 
    struct FShadingBin
    {
        uint16 Triangle = 0xFFFFu;
        uint16 Voxel = 0xFFFFu;
    };
 
    using PrimitiveRasterBinType   = TArray<FRasterBin, TInlineAllocator<1>>;
    using PrimitiveShadingBinType  = TArray<FShadingBin, TInlineAllocator<1>>;
 
    struct FPrimitiveReferences
    {
        const FPrimitiveSceneInfo* SceneInfo = nullptr;
        PrimitiveRasterBinType   RasterBins;
        PrimitiveShadingBinType  ShadingBins;
        bool bWritesCustomDepthStencil = false;
    };
 
    using PrimitiveMapType = Experimental::TRobinHoodHashMap<const FPrimitiveSceneInfo*, FPrimitiveReferences>;
 
public:
    FNaniteVisibility();
 
    void BeginVisibilityFrame();
    void FinishVisibilityFrame();
 
    FNaniteVisibilityQuery* BeginVisibilityQuery(
        FSceneRenderingBulkObjectAllocator& Allocator,
        FScene& Scene,
        const TConstArrayView<FConvexVolume>& ViewList,
        const class FNaniteRasterPipelines* RasterPipelines,
        const class FNaniteShadingPipelines* ShadingPipelines,
        const UE::Tasks::FTask& PrerequisiteTask = {}
    );
 
    PrimitiveRasterBinType*   GetRasterBinReferences(const FPrimitiveSceneInfo* SceneInfo);
    PrimitiveShadingBinType*  GetShadingBinReferences(const FPrimitiveSceneInfo* SceneInfo);
 
    void RemoveReferences(const FPrimitiveSceneInfo* SceneInfo);
 
private:
    FPrimitiveReferences* FindOrAddPrimitiveReferences(const FPrimitiveSceneInfo* SceneInfo);
 
    // Translator should remain valid between Begin/FinishVisibilityFrame. That is, no adding or removing raster bins
    FNaniteRasterBinIndexTranslator BinIndexTranslator;
    TArray<FNaniteVisibilityQuery*, TInlineAllocator<32>> VisibilityQueries;
    TArray<UE::Tasks::FTask, SceneRenderingAllocator> ActiveEvents;
    PrimitiveMapType PrimitiveReferences;
    UE::FMutex Mutex;
    uint8 bCalledBegin : 1;
};
 
namespace Nanite
{
    extern const FNaniteVisibilityResults* GetVisibilityResults(const FNaniteVisibilityQuery* Query);
 
    extern UE::Tasks::FTask GetVisibilityTask(const FNaniteVisibilityQuery* Query);
}
 
class FNaniteScopedVisibilityFrame
{
public:
    FNaniteScopedVisibilityFrame(const bool bInEnabled, FNaniteVisibility& InVisibility)
    : Visibility(InVisibility)
    , bEnabled(bInEnabled)
    {
        if (bEnabled)
        {
            Visibility.BeginVisibilityFrame();
        }
    }
 
    ~FNaniteScopedVisibilityFrame()
    {
        if (bEnabled)
        {
            Visibility.FinishVisibilityFrame();
        }
    }
 
    FORCEINLINE FNaniteVisibility& Get()
    {
        return Visibility;
    }
 
private:
    FNaniteVisibility& Visibility;
    bool bEnabled;
};