PSP/GMO Format

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Last updated: Koral 06:48, 7 Apr 2009 (EDT)

GMO Model-data container


Format Specifications

Information: MrAdults, Ukurere

[GMO] Files consist of various Chunks defining the type of data they contain, with no initial hard-coded offsets in the begining of the file. Each chunk must be parsed seperatly to determine its Type and Size, either to skip it entirey or attempt to extract the information contained within.

As such, parsing these [GMO] files is a similar mechanism to parsing generic 3DS files.

File Header

There is an initial 16-Byte header describing the file as a [GMO]:

   0x00   MAGIC = 0x4f 0x4d 0x47 0x2e 0x30 0x30 0x2e 0x31 0x50 0x53 0x50 0x00 0x00 0x00 0x00
                  "OMG 00 1PSP"

After this comes the first specialised Chunk.


Each Chunk contains an initial local header describing the Type and Size of the contents to come.

   0x00   SHORT   Chunk-Type
   0x02   SHORT   Size of Chunk-Header
   0x04   LONG    Size of Chunk-Data

A number of Chunk-Types have been discovered, described in detail in the sections to follow.

0x0002 - File Start

This Chunk can be described as the root Chunk containing all Sub-Chunks within.

0x0003 - Sub-File

These Chunks mark the exact nature of the Chunks which follow, and can be determined by reading the last SHORT of the chunk.

They usually mark Model or Skeletal data, although there may be more types which are currently undocumented.

Known Values:

  • 0x6f6d Models
  • 0x305f Skeletal Animations

0x0004 - Bone Info

0x0005 - Model Surface

0x0006 - Mesh

0x0007 - Vertex Array

0x0008 - Material

0x0009 - Texture Reference

0x000A - Texture

0x000B - Shared Vertex Data

0x000F - Texture Animation

0x8061 - Mesh Material Info

0x8015 - UV Scale and Bias

0x8066 - Mesh Index Data

0x8081 - Material Texture Blend

0x8082 - Material RGBA

0x8083 - Material Specularity