OBD:Instance file format: Difference between revisions

{{UpdatedForOniX|1.0.0}}<!--Documentation below is waiting to be un-commented.-->

Files in GameDataFolder/ named "level[0-19]_Final.dat", together with ".raw" and sometimes ".sep" counterparts, contain the game data for Oni. These are called "instance files" internally, but a more common-sense name for them is level data files. The format described below was also used for the tool files which supplied the GUI for the in-game editor, however the retail Oni game application refuses to load tool files; for the story behind the tool files, see [[level0_Tools]].

The level 0 files do not contain resources for a specific level but rather resources (instances) shared across all levels. Level 0 is loaded when the game starts and is never unloaded. All other level files, 1-19, are only loaded when their corresponding level starts and then unloaded when it ends. Oni can only hold two level files in memory concurrently. Thus, resources have to be duplicated on disk whenever a character class, sound effect, etc. occurs in more than one level. For instance, although there are only 2,380 unique sounds in the game, there are 7,386 sounds stored across all level data files.

As mentioned, the game's developers used the in-game editor to create AIs, particles, etc. in a level. When one of these developers saved his work, the contents of the level, stored in his PC's RAM, were flushed directly to disk. Thus the structure of the .dat/.raw/.sep files reflects the way in which Bungie West chose to store levels in memory. So when we read the data in the files with a hex editor, we can see eccentricities such as blank space (coming from unused fields and byte-alignment padding) and garbage data (such as now-meaningless pointer values). [[OBD:Raw and separate file formats#Gaps|Further gaps]], mostly representing orphaned obsolete resources, add up to about 25 MB for the whole game.

Here is a walkthrough of an instance file using the level0_Final.dat in English Windows Oni. Follow along in a hex editor for maximum educational value. Each term will be explained in-depth when we fully consider the related data. First, here is how the file begins:

*0x0000000000000000 (blank) - for use with [[OniX]] engine(s)<!--, which instead handle data versioning using the 0x3C field below-->

OniSplit's .oni files use PC 1.0 checksum by default and 1.1 checksums when holding data that is stored differently in the 1.1 format (SNDD, TXMP, AGQG, M3GM, IGSt, TSFT/TSGA, TRAM/TREX) }}