Binary file containers (.mesh, .cmesh, .animation)

Files .mesh, .cmesh, and .animation are containers designed to store multiple files of the same type within a single binary file. The primary purpose of these containers is to reduce the number of individual files in the file system and improve resource loading performance.

Data inside a container is organized as a sequence of chunks. Each chunk begins with a four-character identifier (FourCC, Chunk ID), which defines the type of data stored in the chunk.

The container includes a file table, where each file is represented by its name and data_offset.

The size of each file inside the container, except the last one, is determined by the following formula:

data_size = entries[N + 1].data_offset - entries[N].data_offset

For the last file in the container, its end coincides with the end of the container.

When reading a file, the parser processes chunks sequentially and determines their type by the FourCC value.

Encountering an unknown FourCC value is considered a fatal error. The parser must not skip unknown chunks.

Data structure

PMSH | ANIM | CMHR
MTBL
   entry_count
   entries[entry_count]
       entry_name
       data_offset
   resources[entry_count]
       MESH | EANM | EVLM
           resource_data

Container identifiers

FourCC	Type	Description
PMSH	uint8[4]	Mesh container. Contains .ply resources.
ANIM	uint8[4]	Animation container. Contains .anm resources.
CMHR	uint8[4]	Physics and collision volume container. Contains .vol resources.

Chunk MTBL

Contains a list of all files stored inside the container, as well as offsets to the corresponding data.

Data structure

MTBL
   entry_count
   entries[entry_count]
       entry_name
       data_offset
   resources[entry_count]

Name	Type	Size	Description
FourCC	uint8[4]	4	MTBL
entry_count	uint32	4	Number of entries in the table
entries	struct[entry_count]		Array of container entries

Container entry array (struct)

Name	Type	Size	Description
entry_name	string8	1+	Entry name
data_offset	uint32	4	Offset of the resource data. It’s relative, the end of the MTBL chunk is considered as 0.

Chunk MESH

Contains data in the .ply format.

Name	Type	Description
FourCC	uint8[4]	MESH
ply_data	.ply	Mesh data in the .ply format.

Chunk EANM

Contains data in the .anm format.

Name	Type	Description
FourCC	uint8[4]	EANM
anm_data	.anm	Animation data in the .anm format.

Chunk EVLM

Contains data in the .vol format.

Name	Type	Description
FourCC	uint8[4]	EVLM
vol_data	.vol	Volume data in the .vol format.