LandscapeTextureHash.h

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// Copyright Epic Games, Inc. All Rights Reserved.
 
#pragma once
 
#include "CoreMinimal.h"
#include "Engine/AssetUserData.h"
#include "LandscapeTextureHash.generated.h"
 
class UTexture2D;
 
UENUM()
enum class ELandscapeTextureType : uint8
{
    Unknown,
    Heightmap,
    Weightmap
};
 
UENUM()
enum class ELandscapeTextureUsage : uint8
{
    Unknown,
    EditLayerData,          // used as data for an edit layer, input to the layer merge operation
    FinalData               // used for runtime/rendering
};
 
UCLASS(NotBlueprintable, MinimalAPI, Within = Texture2D)
class ULandscapeTextureHash : public UAssetUserData
{
    GENERATED_BODY()
 
    UPROPERTY()
    FGuid TextureHashGUID;
 
    UPROPERTY()
    FGuid LastSourceID;
 
    // heightmap or weightmap.  When unknown, we fallback to using the texture source ID as hash (old behavior)
    UPROPERTY()
    ELandscapeTextureType TextureType = ELandscapeTextureType::Unknown;
 
    // edit layer data or final data.  When unknown, we fallback to using the texture source ID as hash (old behavior)
    UPROPERTY()
    ELandscapeTextureUsage TextureUsage = ELandscapeTextureUsage::Unknown;
 
    // cache of recently serialized hash values
    // this ensure that if the texture is brought back to match exactly a recently serialized state, it will have exactly the same hash that it was serialized with.
    // This helps us come back to the serialized (presumably cache-friendly) state after no-ops like:  modify + undo, hide layer + unhide layer, etc.
    TMap<FGuid, FGuid> RecentlySerializedHashes;
 
public:
 
#if WITH_EDITORONLY_DATA
    // setup initial state on load, if it doesn't yet exist
    static void SetInitialStateOnPostLoad(UTexture2D* LandscapeTexture, ELandscapeTextureUsage TextureUsage, ELandscapeTextureType TextureType);
 
    // Update the stored hash based on the source data
    static void UpdateHash(UTexture2D* LandscapeTexture, ELandscapeTextureUsage TextureUsage = ELandscapeTextureUsage::Unknown, ELandscapeTextureType TextureType = ELandscapeTextureType::Unknown, bool bForceUpdate = false);
 
    // Explicitly set the hash for the specified LandscapeTexture
    static void SetHash64(UTexture2D* LandscapeTexture, uint64 NewHash, ELandscapeTextureUsage TextureUsage, ELandscapeTextureType TextureType);
 
    // calculate the texture hash directly from the source mip0 contents
    static uint64 CalculateTextureHash64(UTexture2D* LandscapeTexture, ELandscapeTextureType TextureType, bool& bOutHashIsValid);
    static FGuid CalculateTextureHashGUID(UTexture2D* LandscapeTexture, ELandscapeTextureType TextureType, bool& bOutHashIsValid);
 
    // calculate the texture hash from the Mip0Data buffer
    static uint64 CalculateTextureHash64(const FColor* Mip0Data, int32 PixelCount, ELandscapeTextureType TextureType);
 
    // check if the Mip0Data is within the change threshold of OldMip0Data
    static bool DoesTextureDataChangeExceedThreshold(const FColor* Mip0Data, const FColor* OldMip0Data, int32 PixelCount, ELandscapeTextureType TextureType, uint64 OldHash, uint64 NewHash, TOptional<uint8>& OutChangedWeightmapChannelsMasks);
 
    // get the current stored hash for the landscape texture, checking that it is up to date
    static FGuid GetHash(UTexture2D* LandscapeTexture);
 
    // Check the hash is up to date
    static void CheckHashIsUpToDate(UTexture2D* LandscapeTexture);
 
    // UObject Interface
    virtual void Serialize(FArchive& Ar) override;
    virtual bool IsEditorOnly() const override { return true; }
    virtual bool NeedsLoadForClient() const override { return false; }
    virtual bool NeedsLoadForServer() const override { return false; }
#endif // WITH_EDITORONLY_DATA
};