VirtualTextureCollection.h

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// Copyright Epic Games, Inc. All Rights Reserved.
 
#pragma once
 
#include "IndirectVirtualTextureDefinitions.h"
#include "Engine/DataAsset.h"
#include "RenderResource.h"
#include "IndirectVirtualTextureDefinitions.h"
#include "Containers/DynamicRHIResourceArray.h"
#include "Texture2D.h"
#include "TextureCollection.h"
#include "VirtualTexturing.h"
#include "VT/VirtualTextureBuildSettings.h"
#include "VirtualTextureCollection.generated.h"
 
class UVirtualTextureAdapter;
class FTextureResource;
class UTexture;
class UTextureCollection;
struct FTextureCollectionProducerData;
 
struct FVirtualTextureCollectionResource : public FTextureCollectionResource
{
    FVirtualTextureCollectionResource(UVirtualTextureCollection* InParent);
    virtual ~FVirtualTextureCollectionResource() override = default;
 
public: 
    virtual void InitRHI(FRHICommandListBase& RHICmdList) final;
    virtual void ReleaseRHI() override;
 
    struct FTextureEntry
    {
        // Optional, the virtual producer
        FVirtualTextureProducerHandle VirtualProducerHandle;
 
        // Optional, physical texture
        // Keep the GT object around since RT resources may be released
        UTexture* PhysicalTexture = nullptr;
 
        // If true, this entry will be converted internally to the physical format
        // This also includes compression
        bool bRequiresAdapter = false;
 
        // The format of this texture, before adaptation
        EPixelFormat Format = PF_Unknown;
 
        // Number of blocks in this entry
        FUintVector2 BlockCount;
    };
    
    UE::HLSL::FIndirectVirtualTextureUniform GetVirtualPackedUniform() const;
    
    FRHIShaderResourceView* GetVirtualCollectionRHI() const
    {
        check(VirtualCollectionRHISRV);
        return VirtualCollectionRHISRV;
    }
 
    FRHITexture* GetVirtualPageTable() const
    {
        return PageTable;
    }
    
    FRHIShaderResourceView* GetVirtualPhysicalTextureSRV() const
    {
        return PhysicalTextureSRV;
    }
 
    FVirtualTextureProducerHandle GetProducerHandle() const
    {
        return ProducerHandle;
    }
    
private:
    void FindFirstFormat();
    
    void FindConservativeFormat();
 
    void ComputeLayout(FTextureCollectionProducerData& Data);
    
    void CreateIndexTable(FTextureCollectionProducerData& Data);
 
    void FormatCollectionError(const TCHAR* Reason, uint32 TextureIndex);
 
private:
    TArray<UTexture*> Textures;
 
    FVirtualTextureBuildSettings BuildSettings;
 
    FBufferRHIRef             VirtualCollectionRHI;
    FRHIShaderResourceViewRef VirtualCollectionRHISRV;
 
    FRHITexture*            PageTable          = nullptr;
    FRHIShaderResourceView* PhysicalTextureSRV = nullptr;
 
    IAllocatedVirtualTexture*     AllocatedVT = nullptr;
    FVirtualTextureProducerHandle ProducerHandle;
    
    TResourceArray<UE::HLSL::FIndirectVirtualTextureEntry> VirtualUniforms;
 
    EPixelFormat Format         = PF_Unknown;
    bool bIsSRGB                = false;
    bool bAllowFormatConversion = false;
};
 
UCLASS(MinimalAPI, Experimental)
class UVirtualTextureCollection : public UTextureCollection
{
    GENERATED_BODY()
 
public: 
    UPROPERTY(EditAnywhere, Category=VirtualTextureCollection)
    bool bAllowFormatConversion = true;
 
    UPROPERTY(EditAnywhere, Category=VirtualTextureCollection, meta = (editcondition = "bAllowFormatConversion"))
    bool bIsSRGB = true;
 
    UPROPERTY(VisibleAnywhere, Category=VirtualTextureCollection, AdvancedDisplay)
    TEnumAsByte<EPixelFormat> RuntimePixelFormat = PF_Unknown;
    
public: 
#if WITH_EDITOR
    virtual void PostEditChangeProperty(FPropertyChangedEvent& PropertyChangedEvent) override;
#endif // WITH_EDITOR
    virtual void BeginDestroy() override;
 
    virtual FTextureCollectionResource* CreateResource() override;
    virtual bool IsVirtualCollection() const override { return true; }
 
protected:
    friend struct FVirtualTextureCollectionResource;
    
#if WITH_EDITOR
    void ValidateVirtualCollection();
    void FormatCollectionError(const TCHAR* Reason, uint32 TextureIndex);
#endif //  WITH_EDITOR
};