After the RFRM Header, the first section of the file is SKHD in SMDL, and WDHD in WMDL. Following those extra sections, all three formats start with a header.
HEAD
| Offset
|
Size
|
Description
|
| 0x0
|
24
|
"HEAD" Chunk Descriptor
|
| 0x18
|
4
|
Unknown
|
| 0x1C
|
4
|
Unknown
|
| 0x20
|
4
|
Unknown
|
| 0x24
|
4
|
Unknown
|
| 0x28
|
4
|
Unknown
|
| 0x2C
|
24
|
Axis-aligned bounding box
|
| 0x30
|
4
|
Extra data flag
|
If the ending flag is 1, then a large chunk of extra data follows before the next section begins; otherwise, the HEAD section ends.
MTRL
The MTRL section has a 32-bit material count, then lays out its materials one after the other. The material structure is somewhat complicated; each material has a name, something that wasn't present in Retro's previous material formats, as well as a shader ID. The rest of the material structure appears to be defining parameters to pass to the shader. This needs a lot more research to determine what the parameters are and what the different data is.
| Type
|
Size
|
Description
|
| string
|
-
|
Name (zero-terminated)
|
| MTRL
|
16
|
Shader ID
|
| char[4]
|
4
|
Shading type fourCC; can be PHNG, LAMB, SURF, or FURM
|
| u32
|
4
|
Unknown
|
| u32
|
4
|
Subsection count
|
Material subsections each have a fourCC name and a type identifer, followed by a set of parameters. The type and number of parameters is dependent on the subsection type; there are five known types currently.
| Offset
|
Type
|
Size
|
Description
|
| 0x0
|
char[4]
|
4
|
Section name fourCC
|
| 0x4
|
u32
|
4
|
Section type
|
| 0x8
|
struct
|
-
|
Section data struct; type varies based on the section type value
|
| End of subsection; next one begins
|
Type 0: Texture Map
| Offset
|
Type
|
Size
|
Description
|
| 0x0
|
TXTR
|
0x10
|
Texture ID
|
| 0x10
|
u32
|
4
|
Unknown
|
| 0x14
|
u32
|
4
|
Unknown
|
| 0x18
|
u32
|
4
|
Unknown
|
| 0x1C
|
u32
|
4
|
Unknown
|
| 0x20
|
u32
|
4
|
Unknown
|
| 0x24
|
End of struct
|
Type 1: Unknown
| Offset
|
Type
|
Size
|
Description
|
| 0x0
|
float
|
4
|
Unknown
|
| 0x4
|
float
|
4
|
Unknown
|
| 0x8
|
float
|
4
|
Unknown
|
| 0xC
|
float
|
4
|
Unknown
|
| 0x10
|
End of struct
|
Type 2: Unknown
| Offset
|
Type
|
Size
|
Description
|
| 0x0
|
float
|
4
|
Unknown
|
| 0x4
|
End of struct
|
Type 4: Unknown
| Offset
|
Type
|
Size
|
Description
|
| 0x0
|
u32
|
4
|
Unknown
|
| 0x4
|
float
|
4
|
Unknown
|
| 0x8
|
float
|
4
|
Unknown
|
| 0xC
|
float
|
4
|
Unknown
|
| 0x10
|
float
|
4
|
Unknown
|
| 0x14
|
float
|
4
|
Unknown
|
| 0x18
|
float
|
4
|
Unknown
|
| 0x1C
|
float
|
4
|
Unknown
|
| 0x20
|
u32
|
4
|
Unknown
|
| 0x24
|
u32
|
4
|
Unknown
|
| 0x28
|
u32
|
4
|
Unknown
|
| 0x2C
|
u32
|
4
|
Unknown
|
| 0x30
|
u32
|
4
|
Unknown
|
| 0x34
|
u8
|
1
|
Unknown
|
| 0x35
|
TXTR
|
0x10
|
Unknown Texture ID
|
| 0x45
|
u32
|
4
|
Unknown
|
| 0x49
|
u32
|
4
|
Unknown
|
| 0x4D
|
u32
|
4
|
Unknown
|
| 0x51
|
u32
|
4
|
Unknown
|
| 0x55
|
u32
|
4
|
Unknown
|
| 0x59
|
TXTR
|
0x10
|
Unknown Texture ID
|
| 0x69
|
u32
|
4
|
Unknown
|
| 0x6D
|
u32
|
4
|
Unknown
|
| 0x71
|
u32
|
4
|
Unknown
|
| 0x75
|
u32
|
4
|
Unknown
|
| 0x79
|
u32
|
4
|
Unknown
|
| 0x7D
|
u32
|
4
|
Unknown
|
| 0x81
|
u32
|
4
|
Unknown
|
| 0x85
|
u32
|
4
|
Unknown
|
| 0x89
|
u32
|
4
|
Unknown
|
| 0x8D
|
End of struct
|
Type 5: Unknown
| Offset
|
Type
|
Size
|
Description
|
| 0x0
|
u32
|
4
|
Unknown
|
| 0x4
|
u32
|
4
|
Unknown
|
| 0x8
|
u32
|
4
|
Unknown
|
| 0xC
|
u32
|
4
|
Unknown
|
| 0x10
|
End of struct
|
MESH
The MESH section does what the name suggests: it defines submeshes. The MESH section header is as follows:
| Offset
|
Size
|
Description
|
| 0x0
|
24
|
MESH Chunk Descriptor
|
| 0x18
|
4
|
Submesh count
|
| 0x1C
|
End of MESH header
|
Each submesh definition is structured as follows:
| Offset
|
Size
|
Description
|
| 0x0
|
4
|
Unknown; always 3?
|
| 0x4
|
2
|
Material ID
|
| 0x6
|
1
|
Vertex buffer ID
|
| 0x7
|
1
|
Index buffer ID
|
| 0x8
|
4
|
Start index
|
| 0xC
|
4
|
Index count
|
| 0x10
|
4
|
Unknown
|
| 0x14
|
1
|
Unknown; usually seems to be either 0 or 1, possibly a bool value
|
| 0x15
|
End of submesh definition
|
VBUF
The VBUF section defines vertex buffers; each buffer can have different vertex types, with different strides and attributes.
| Offset
|
Size
|
Description
|
| 0x0
|
24
|
VBUF Chunk Descriptor
|
| 0x18
|
4
|
Vertex buffer count
|
| 0x1C
|
End of VBUF header
|
Vertex Buffer
| Offset
|
Size
|
Description
|
| 0x0
|
4
|
Vertex count
|
| 0x4
|
4
|
Attrib count (AC)
|
| 0x8
|
0x14 × AC
|
Vertex attributes
|
| End of vertex buffer
|
Vertex Attribute
| Offset
|
Size
|
Description
|
| 0x0
|
4
|
Unknown
|
| 0x4
|
4
|
Offset
|
| 0x8
|
4
|
Stride
|
| 0xC
|
4
|
Unknown
|
| 0x10
|
4
|
Unknown (likely attrib type/format)
|
| 0x14
|
End of attribute
|
IBUF
Just like how the VBUF section defines vertex buffers, the IBUF section defines index buffers. Each index buffer only has one value associated with it, so it's fairly simple, and you generally will only see one or two index buffers per file.
| Offset
|
Size
|
Description
|
| 0x0
|
24
|
IBUF Chunk Descriptor
|
| 0x18
|
4
|
Index buffer count
|
| 0x1C
|
End of IBUF header
|
Index Buffer
| Offset
|
Size
|
Description
|
| 0x0
|
4
|
Format (1 means unsigned short; 2 means unsigned long)
|
| 0x4
|
End of index buffer
|
GPU
The GPU section contains raw buffer data that's fed to the GPU. It's essentially just a giant blob with all the vertex and index buffers laid out next to each other. The tricky part is, all the buffer data is LZSS-compressed, and the metadata needed to decompress it is stored in the pak rather than in the files themselves; not only that, but that metadata is also the only way to distinguish the different buffers from each other.
As such, this section can't be read correctly if the model file is unpacked and completely left as-is; it needs to be either read directly from the pak, or the metadata needs to be added to the file in some way. A good unpacker should append the metadata to the end of the file; a pre-decompressed file needs the buffer sizes or offsets inserted into the file data somewhere.
The pak metadata for the model formats contains mainly information related to the size and layout of the GPU section, and the metadata required to locate and decompress specific buffers within it.
| Offset
|
Size
|
Description
|
| 0x0
|
4
|
Unknown; always 4?
|
| 0x4
|
4
|
GPU section offset
|
| 0x8
|
4
|
GPU chunk count (CC)
|
| 0xC
|
8 × CC
|
GPU chunk definitions
|
| -
|
4
|
Compressed vertex buffer count (VC)
|
| -
|
0x10 × VC
|
Vertex buffer definitions
|
| -
|
4
|
Compressed index buffer count (IC)
|
| -
|
0x10 × IC
|
Index buffer definitions
|
| End of pak metadata
|
GPU Chunk
For large models, the GPU section might be split up into multiple chunks, rather than read as one data buffer; all offsets into the GPU section will be relative to the start of the chosen chunk.
| Offset
|
Size
|
Description
|
| 0x0
|
4
|
Size
|
| 0x4
|
4
|
Offset
|
| 0x8
|
End of GPU chunk definition
|
Compressed Buffer
The format for compressed buffer definitions is the same regardless of buffer type (vertex/index).
| Offset
|
Size
|
Description
|
| 0x0
|
4
|
GPU chunk index
|
| 0x4
|
4
|
Start offset (relative to the start of the chosen GPU chunk)
|
| 0x8
|
4
|
Compressed size
|
| 0xC
|
4
|
Decompressed size
|
| 0x10
|
End of compressed buffer definition
|
