OBD:Instance file format: Difference between revisions

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{{Hatnote|".dat" redirects here; for other files ending in ".dat", see [[Oni (folder)]].<br>

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.

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==Blank space and garbage==

The structure of the level data files 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 and random RAM contents from uninitialized memory. There are also [[OBD:Raw and separate file formats#Gaps|gaps in the .raw/.sep files]], mostly representing orphaned obsolete resources, which add up to about 25 MB for the whole game.

*0x0003BA70A8DBAE11 - templates compatible with PlayStation 2 engine

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

{{OBDtr| 0x08 | uint32  | | 31 33 52 56 | '13RV'    | .dat version (meant to be read as "VR31")<br>OniSplit's .oni files use '23RV' ("VR32") instead<!--<br>OniX's [[Oni (folder)|GDFX]] uses '33RV' ("VR33") to signify that the new data versioning system is in use--> }}

{{OBDtr| 0x0C | uint16  | | 40 00      | 64        | size of this header }}

{{OBDtr| 0x12 | uint16  | | 08 00      | 8        | size of name descriptor }}

{{OBDtr| 0x14 | uint32  | | 83 24 00 00 | 9347      | instance descriptor count  }}

{{OBDtr| 0x20 | uint32  | | A0 BC 03 00 | 0x03BCA0  | data block offset }}

{{OBDtr| 0x24 | uint32  | | A0 35 25 00 | 2438560  | data block size }}

{{OBDtr| 0x2C | uint32  | | 04 4F 02 00 | 151300    | name block size }}

{{OBDtr| 0x38 | uint32  | | F4 55 5F 00 | (garbage) | unused<!--used by OniX for data versioning; the three high bytes contains the highest data version (timestamp) found in any instance in this .dat; see instance descriptor table's 0x10 for format--> }}

{{OBDtr| 0x3C | uint32  | | 90 4F 63 00 | (garbage) | unused<!--used by OniX for content versioning; the three high bytes contain the highest content version (timestamp) found in any instance in this .dat; see instance descriptor table's 0x10 for format--> }}

The '''descriptor counts''' are the sizes of arrays which are coming up in this file: the instance, name and template descriptors. For instance, the size of the instance descriptor array will be 0x2483, or 9,347 items, in length.

That concludes the header of the instance file. Immediately after this header we find the instance descriptors array.

==Data block==

The reason we'd need to align to 32 bytes is that the start of each instance's record (the instance ID) is always 32 byte-aligned. Thus, even though the template descriptors ended at 0x03BC9C, there are four empty bytes here so that the data block can begin at 0x03BCA0, which divides evenly by 32. This alignment rule also means that the instance-specific data will always start at an offset like 0x0008, 0x0028, 0x0148, etc.  

==Name block==

{{Table}}

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