VirtualTextureFeedback.h

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// Copyright Epic Games, Inc. All Rights Reserved.
 
#pragma once
 
#include "CoreMinimal.h"
#include "RenderResource.h"
#include "VT/VirtualTextureFeedbackBuffer.h"
 
class FVirtualTextureFeedback : public FRenderResource
{
public:
    FVirtualTextureFeedback();
    ~FVirtualTextureFeedback();
 
    void TransferGPUToCPU(FRHICommandList& RHICmdList, FBufferRHIRef const& Buffer, FVirtualTextureFeedbackBufferDesc const& Desc);
    void TransferGPUToCPU(FRDGBuilder& GraphBuilder, class FRDGBuffer* Buffer, FVirtualTextureFeedbackBufferDesc const& Desc);
 
    bool CanMap(FRHICommandListImmediate& RHICmdList);
 
    struct FMapResult
    {
        // Feedback Data is .X=PageId, .Y=PageCount
        FUintPoint* RESTRICT Data = nullptr;
        uint32 Size = 0;
        int32 MapHandle = -1;
    };
 
    FMapResult Map(FRHICommandListImmediate& RHICmdList);
    FMapResult Map(FRHICommandListImmediate& RHICmdList, int32 MaxTransfersToMap);
    
    void Unmap(FRHICommandListImmediate& RHICmdList, int32 MapHandle);
 
protected:
    //~ Begin FRenderResource Interface
    virtual void InitRHI(FRHICommandListBase& RHICmdList) override;
    virtual void ReleaseRHI() override;
    //~ End FRenderResource Interface
 
private:
    struct FFeedbackItem
    {
        FVirtualTextureFeedbackBufferDesc Desc;
        FRHIGPUMask GPUMask;
        FStagingBufferRHIRef StagingBuffer;
    };
 
    static const uint32 MaxTransfers = 8u;
    FFeedbackItem FeedbackItems[MaxTransfers];
 
    class FFeedbackGPUFencePool* Fences;
 
    int32 NumPending;
    uint32 WriteIndex;
    uint32 ReadIndex;
 
    struct FMapResources
    {
        int32 FeedbackItemToUnlockIndex = -1;
        TArray<FUintPoint> ResultData;
    };
 
    TArray<FMapResources> MapResources;
    TArray<int32> FreeMapResources;
};
 
extern TGlobalResource< FVirtualTextureFeedback > GVirtualTextureFeedback;