Unreal Engine 4 UASSET UEXP

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UASSET, UEXP

• Format Type : Archive
  
• Endian Order : Little Endian
  
• Signature : C1 83 2A 9E
  

Format Specifications

Unreal Engine 4 uasset file
DETAILS OF THE IMPORT DIRECTORY...
The ParentDirectoryNameID is the name
The first few entries in the Import directory is ClassID = "Class" and NameID = the main data type (eg "Texture2D", "Material")
The last entry is ClassID = "Package" and NameID = the main package name (eg "/Script/Engine")
FILE HEADER
  uint32 {4}       - Unreal Signature (193,131,42,158) // C1 83 2A 9E
  uint32 {4}       - Version (6) (XOR with 255)
  byte {16}        - null
  uint32 {4}       - File Directory Offset?
  uint32 {4}       - Unknown (5)
  uint32 {4}       - Package Name (None)
  uint32 {4}       - null
  byte {1}         - Unknown (128)
  uint32 {4}       - Number of Names
  uint32 {4}       - Name Directory Offset
  uint64 {8}       - null
  uint32 {4}       - Number Of Exports
  uint32 {4}       - Exports Directory Offset
  uint32 {4}       - Number Of Imports
  uint32 {4}       - Import Directory Offset
  byte {20}        - null
  byte {16}        - GUID Hash
  uint32 {4}       - Unknown (1)
  uint32 {4}       - Unknown (1/2)
  uint32 {4}       - Unknown (Number of Names - again?)
  byte {36}        - null
  uint32 {4}       - Unknown
  uint32 {4}       - null
  uint32 {4}       - Padding Offset
  uint32 {4}       - File Length [+4] (not always - sometimes an unknown length/offset)
  byte {12}        - null
  uint32 {4}       - Unknown (-1)
  uint32 {4}       - Files Data Offset

NAMES DIRECTORY
  for each name
    uint32 {4}       - Name Length (including null)
    byte {X}         - Name
    byte {1}         - null Name Terminator
    uint32 {4}       - Flags

IMPORT DIRECTORY
  for each import (28 bytes per entry)
    uint64 {8}       - Parent Directory Name ID
    uint64 {8}       - Class ID (ID to "Package", "Class", etc)
    uint32 {4}       - Parent Import Object ID (-1 for no parent) (XOR with 255)
    uint32 {4}       - Name ID
    uint32 {4}       - Unknown ID

EXPORTS DIRECTORY
  for each export (100 bytes per entry)
    byte {100}       - Unknown

PADDING
  uint32 {4}       - null

FILE DATA
  for each file ???
    for each property (continue until NameID == "None")
      uint64 {8}       - Name ID
      if (NameID != None){
        uint64 {8}       - Class ID
        uint64 {8}       - Length Property
        if (classID == StructProperty){
          uint64 {8}       - Class ID
          uint64 {8}       - null
          uint64 {8}       - null
          if (classID == IntPoint){
            byte {1}         - null
            uint32 {4}       - Point X
            uint32 {4}       - Point Y
            }

          else if (classID == Guid){
            byte {1}         - null
            byte {16}        - GUID
            }

          else if (classID == ColorMaterialInput){
            byte {1}         - null
            byte {X}         - Color Material Input Data (the length of X = LengthProperty from above)
            }

          else if (classID == ScalarMaterialInput){
            byte {1}         - null
            byte {X}         - Scalar Material Input Data (the length of X = LengthProperty from above)
            }

          else if (classID == TextureStreamingData){
            byte {1}         - null
            uint64 {8}       - null
            uint64 {8}       - null
            }

          else if (classID == MaterialTextureInfo){
            byte {1}         - null
            Now keep reading properties until a "None" is reached - all these properties form the MaterialTextureInfo class
            }

          else if (classID == FontCharacter){
            byte {1}         - null
            uint32 {4}       - Unknown
            uint32 {4}       - Unknown
            uint32 {4}       - Unknown
            uint64 {8}       - Unknown
            }

          else if (classID == FontImportOptionsData){
            byte {1}         - null
            Now keep reading properties until a "None" is reached - all these properties form the FontImportOptionsData class
            These fields come after the property reading above
            uint64 {8}       - Class ID (points to None)
            uint32 {4}       - null
            uint32 {4}       - Extra Data Length [*4]
            byte {X}         - Extra Data
            }

          else {
            use the structure of one of the other properties (eg BoolProperty, ByteProperty, etc)
            }

          }

        else if (classID == BoolProperty){
          uint16 {2}       - Boolean Value (0/1)
          }

        else if (classID == FloatProperty){
          byte {1}         - null
          uint32 {4}       - Float Value
          }

        else if (classID == NameProperty){
          byte {1}         - null
          uint32 {4}       - Name ID
          uint32 {4}       - Unknown
          }

        else if (classID == IntProperty){
          byte {1}         - null
          uint32 {4}       - Integer Value
          }

        else if (classID == StrProperty){
          byte {1}         - null
          uint32 {4}       - String Length (including null terminator)
          byte {X}         - String
          byte {1}         - null String Terminator
          }

        else if (classID == ObjectProperty){
          uint32 {4}       - Property
          }

        else if (classID == ByteProperty){
          byte {X}         - Bytes (the length of X = LengthProperty from above)
          byte {1}         - null
          byte {X}         - Bytes (the length of X = LengthProperty from above)
          }

        else if (classID == ArrayProperty){
          uint64 {8}       - Class ID
          byte {1}         - null
          NOTE: LengthProperty from above gives the length of the next 4-byte field and the full contents of the array "for" loop
          uint32 {4}       - Number of Values in the Array
          if (classID == StructProperty){
            first comes the normal 4-field handler
            uint64 {8}       - Name ID
            uint64 {8}       - Class ID
            uint64 {8}       - Length Property
            then comes the normal StructProperty handler
            uint64 {8}       - Class ID <-- this is the Class for each item in the array
            uint64 {8}       - null
            uint64 {8}       - null
            }

          for each value in the array {
            use the structure of one of the other properties (eg BoolProperty, ByteProperty, etc)
            Either use the ClassID from the ArrayProperty definition, or if that is a StructProperty, use the ClassID in the StructProperty handler (details above)
            }

          if (classID == StructProperty && numberOfValuesInArray > 1){
            byte {1}         - null
            }

          }

        }

      uint32 {4}       - null
      uint16 {2}       - Flags (1/3)
      uint16 {2}       - Flags (1/0)
      uint32 {4}       - Unknown (1)
      uint64 {8}       - Type ID (points to "PF_DXT5", "PF_B8G8R8A8", etc for a Texture2D Image)

    if (typeID == PF_DXT5 || PF_DXT3 || PF_DXT1){
      uint32 {4}       - Offset to Largest Mipmap [+8]
      uint32 {4}       - Original Image Width
      uint32 {4}       - Original Image Height
      uint32 {4}       - Unknown (1)
      uint32 {4}       - Type Name Length (including null) (8)
      byte {7}         - Type Name (PF_DXT5/3/1)
      byte {1}         - null Type Name Terminator
      uint32 {4}       - null
      uint32 {4}       - Mipmap Count
      for each large mipmap (where width/height >= 128), starting with largest mipmap and decreasing each time by /2
        uint32 {4}       - Entry Indicator (1)
        uint32 {4}       - Flags (1025)
        uint32 {4}       - Length of Mipmap Data
        uint32 {4}       - Length of Mipmap Data
        uint64 {8}       - Relative Offset to this mipmap (relative to the start of the largest mipmap data)
        uint32 {4}       - This Mipmap Width
        uint32 {4}       - This Mipmap Height

      for each Small Mipmap...
        uint32 {4}       - Entry Indicator (1)
        uint32 {4}       - Flags (72)
        uint32 {4}       - Length of Mipmap Data
        uint32 {4}       - Length of Mipmap Data
        uint64 {8}       - Offset to start of Mipmap Data
        byte {X}         - DXT5/3/1 Pixel Data
        uint32 {4}       - This Mipmap Width
        uint32 {4}       - This Mipmap Height

      uint32 {4}       - Mipmap Count
      uint32 {4}       - null
      for each large mipmap (where width/height >= 128), starting with largest mipmap and decreasing each time by /2
        byte {X}         - DXT5/3/1 Pixel Data

      }

    else if (typeID == PF_B8G8R8A8){
      uint32 {4}       - Offset to Largest Mipmap [+8]
      uint32 {4}       - Original Image Width
      uint32 {4}       - Original Image Height
      uint32 {4}       - Unknown (1)
      uint32 {4}       - Type Name Length (including null) (12)
      byte {11}        - Type Name (PF_B8G8R8A8)
      byte {1}         - null Type Name Terminator
      uint32 {4}       - null
      uint32 {4}       - Mipmap Count
      for each large mipmap (where width/height >= 128), starting with largest mipmap and decreasing each time by /2
        uint32 {4}       - Entry Indicator (1)
        uint32 {4}       - Flags (1025)
        uint32 {4}       - Length of Mipmap Data
        uint32 {4}       - Length of Mipmap Data
        uint64 {8}       - Relative Offset to this mipmap (relative to the start of the largest mipmap data)
        uint32 {4}       - This Mipmap Width
        uint32 {4}       - This Mipmap Height

      for each Small Mipmap...
        uint32 {4}       - Entry Indicator (1)
        uint32 {4}       - Flags (72)
        uint32 {4}       - Length of Mipmap Data
        uint32 {4}       - Length of Mipmap Data
        uint64 {8}       - Offset to start of Mipmap Data
        byte {X}         - BGRA Pixel Data
        uint32 {4}       - This Mipmap Width
        uint32 {4}       - This Mipmap Height

      uint32 {4}       - Mipmap Count
      uint32 {4}       - null
      for each large mipmap (where width/height >= 128), starting with largest mipmap and decreasing each time by /2
        byte {X}         - BGRA Pixel Data

      }

    else if (typeID == PF_BC5){
      uint32 {4}       - Offset to Largest Mipmap [+8]
      uint32 {4}       - Original Image Width
      uint32 {4}       - Original Image Height
      uint32 {4}       - Unknown (1)
      uint32 {4}       - Type Name Length (including null) (7)
      byte {6}         - Type Name (PF_BC5)
      byte {1}         - null Type Name Terminator
      uint32 {4}       - Unknown (1)
      uint32 {4}       - Mipmap Count
      for each large mipmap (where width/height >= 128), starting with largest mipmap and decreasing each time by /2
        uint32 {4}       - Entry Indicator (1)
        uint32 {4}       - Flags (1025)
        uint32 {4}       - Length of Mipmap Data
        uint32 {4}       - Length of Mipmap Data
        uint64 {8}       - Relative Offset to this mipmap (relative to the start of the largest mipmap data)
        uint32 {4}       - This Mipmap Width
        uint32 {4}       - This Mipmap Height

      for each small mipmap (where width/height < 128), decreasing each time by /2..
        uint32 {4}       - Entry Indicator (1)
        uint32 {4}       - Flags (72)
        uint32 {4}       - Length of Mipmap Data
        uint32 {4}       - Length of Mipmap Data
        uint64 {8}       - Offset to start of Mipmap Data
        byte {X}         - BC5 Pixel Data
        uint32 {4}       - This Mipmap Width
        uint32 {4}       - This Mipmap Height

      uint32 {4}       - Mipmap Count
      uint32 {4}       - null
      for each large mipmap (where width/height >= 128), starting with largest mipmap and decreasing each time by /2
        byte {X}         - BC5 Pixel Data

      }

    else if (typeID == PF_G8){
      uint32 {4}       - Length of Image Data?
      uint32 {4}       - Image Width
      uint32 {4}       - Image Height
      uint32 {4}       - Unknown (1)
      uint32 {4}       - Type Name Length (including null) (6)
      byte {5}         - Type Name (PF_G8)
      byte {1}         - null Type Name Terminator
      uint32 {4}       - null
      uint32 {4}       - Mipmap Count (1)
      uint32 {4}       - Unknown (1)
      uint32 {4}       - Flags? (72)
      uint32 {4}       - Length of Mipmap Data
      uint32 {4}       - Length of Mipmap Data
      uint64 {8}       - Offset to start of Mipmap Data (absolute offset)
      byte {X}         - Greyscale Pixel Data
      uint32 {4}       - Image Width
      uint32 {4}       - ImageHeight
      uint64 {8}       - Unknown (28)
      }

    else {
      NOT A TEXTURE IMAGE (or an unknown Texture format)
      byte {X}         - File Data
      }

FILE FOOTER
  uint32 {4}       - Unreal Signature (193,131,42,158) // C1 83 2A 9E

MultiEx BMS Script

Not written yet.

Notes and Comments

• Archives may be splitted to .uasset and .uexp files - the first one contains file header, second one - all the data.
• There is a method to make working translations for games when UEXP files contain only text data:
  1. Parse uexp file and extract text.
  2. Translate text to your language
  3. Rebuild uexp file. Add 4-byte footer at the end of the file.
  4. Update uexp size in the uasset's footer.

Games

List of games using this file format:

• Black Legend (*.uasset / *.uexp)
• Bravely Default II (*.uasset / *.uexp)
• Daymare: 1994 Sandcastle (*.uasset / *.uexp)
• Dreadout 2 (*.uasset / *.uexp)
• GUILTY GEAR -STRIVE- (*.uasset / *.uexp)
• Man of Medan (*.uasset / *.uexp)
• Martha Is Dead (*.uasset / *.uexp)
• Marvel vs. Capcom: Infinite (*.uasset)
• Monkey King: Hero is Back (*.uasset / *.uexp)
• My Hero One's Justice 2 (*.uasset / *.uexp)
• No More Heroes 3 (*.uasset / *.uexp)
• Pumpkin Jack (PC) (*.uasset)
• Remothered Tormented Fathers (PC) (*.uasset)
• Shinobi Striker (*.uasset)
• Soul Calibur VI (*.uasset)
• Tekken 7 (PC) (*.uasset)
• The Sinking City (*.uasset / *.uexp)
• Triangle Strategy (Switch) (*.uasset / *.uexp)
• many more...

Compatible Programs

See List of Unreal Engine Tools article on this wiki.

See Also

• Unreal Engine 4 PAK (xentax wiki)

Gallery

• 

  FModel

• 

  Asset Editor