Urho3D尽可能使用现有文件格式，仅在绝对必要时才定义自定义文件格式。当前使用的自定义文件格式有：

二进制模型格式（.mdl）

 Model geometry and vertex morph data

byte[4]    Identifier "UMDL" or "UMD2"

uint       Number of vertex buffers

  For each vertex buffer:

  uint       Vertex count

  uint       Legacy vertex element mask (determines vertex size)

  uint       Morphable vertex range start index

  uint       Morphable vertex count

  byte[]     Vertex data (vertex count * vertex size)

  In "UMD2" format, the legacy vertex element mask is replaced with the following:

  uint       Vertex element count

  uint[]     Descriptions for each vertex element, where

             bits 0-7 = element data type, bits 8-15 = semantic, bits 16-23 = semantic index

uint    Number of index buffers

  For each index buffer:

  uint       Index count

  uint       Index size (2 for 16-bit indices, 4 for 32-bit indices)

  byte[]     Index data (index count * index size)

uint    Number of geometries

  For each geometry:

  uint       Number of bone mapping entries

  uint[]     Bone mapping data, Maps geometry bone indices to global bone indices for HW skinning.

             May be empty, in this case identity mapping will be used.

  uint       Number of LOD levels

    For each LOD level:

    float      LOD distance

    uint       Primitive type (0 = triangle list, 1 = line list)

    uint       Vertex buffer index, starting from 0

    uint       Index buffer index, starting from 0

    uint       Draw range: index start

    uint       Draw range: index count

uint    Number of vertex morphs (may be 0)

  For each vertex morph:

  cstring    Name of morph

  uint       Number of affected vertex buffers

    For each affected vertex buffer:

    uint       Vertex buffer index, starting from 0

    uint       Vertex element mask for morph data. Only positions, normals & tangents are supported.

    uint       Vertex count

      For each vertex:

      uint       Vertex index

      Vector3    Position (if included in the mask)

      Vector3    Normal (if included in the mask)

      Vector3    Tangent (if included in the mask)

Skeleton data

uint       Number of bones (may be 0)

  For each bone:

  cstring    Bone name

  uint       Parent bone index starting from 0. Same as own bone index for the root bone

  Vector3    Initial position

  Quaternion Initial rotation

  Vector3    Initial scale

  float[12]  4x3 offset matrix for skinning

  byte       Bone collision info bitmask. 1 = bounding sphere 2 = bounding box

  If bounding sphere data included:

  float      Bone radius

  If bounding box data included:

  Vector3    Bone bounding box minimum

  Vector3    Bone bounding box maximum

Bounding box data

Vector3    Model bounding box minimum

Vector3    Model bounding box maximum

Geometry center data

  For each geometry:

  Vector3    Geometry center

 

二进制动画格式（.ani）

byte[4]    Identifier "UANI"

cstring    Animation name

float      Length in seconds

uint       Number of tracks

  For each track:

  cstring    Track name (practically same as the bone name that should be driven)

  byte       Mask of included animation data. 1 = bone positions 2 = bone rotations 4 = bone scaling

  uint       Number of keyframes

    For each keyframe:

    float      Time position in seconds

    Vector3    Position (if included in data)

    Quaternion Rotation (if included in data)

    Vector3    Scale (if included in data)

注意：动画是使用绝对骨骼变换存储的。因此，仅支持动画之间的lerp混合；附加姿势修改不是。

Direct3D9二进制着色器格式（.vs3，.ps3）

byte[4]    Identifier "USHD"

short      Shader type (0 = vertex, 1 = pixel)

short      Shader model (3)

uint       Number of constant parameters

    For each constant parameter:

    cstring    Parameter name

    byte       Register index

    byte       Number of registers

uint       Number of texture units

    For each texture unit:

    cstring    Texture unit name

    byte       Sampler index

uint       Bytecode size

byte[]     Bytecode

Direct3D11二进制着色器格式（.vs4、.ps4）

byte[4]    Identifier "USHD"

short      Shader type (0 = vertex, 1 = pixel)

short      Shader model (4)

uint       Vertex element hash code (0 for pixel shaders)

uint       Number of constant parameters

    For each constant parameter:

    cstring    Parameter name

    byte       CBuffer index

    uint       Start byte offset in CBuffer

    uint       Byte size

uint       Number of texture units

    For each texture unit:

    cstring    Texture unit name

    byte       Sampler index

uint       Bytecode size

byte[]     Bytecode

包文件（.pak）

byte[4]    Identifier "UPAK" or "ULZ4" if compressed

uint       Number of file entries

uint       Whole package checksum

    For each file entry:

    cstring    Name

    uint       Start offset

    uint       Size

    uint       Checksum

    The compressed data for each file is the following, repeated until the file is done:

    ushort     Uncompressed length of block

    ushort     Compressed length of block

    byte[]     Compressed data

编译的AngelScript（.asc）    

byte[4]    Identifier "ASBC"

byte[]     Bytecode, produced by AngelScript serializer