PAK (Metroid Prime): Difference between revisions
→File Order
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Additionally, in Prime 2 any files can be left uncompressed if the compressed file is larger than the uncompressed one. This is not the case in Prime 1 (although custom repacking implementations should probably do this regardless). | Additionally, in Prime 2 any files can be left uncompressed if the compressed file is larger than the uncompressed one. This is not the case in Prime 1 (although custom repacking implementations should probably do this regardless). | ||
== | == Optimizing Load Times == | ||
When rebuilding new paks, it's extremely important that asset order be optimized in order to minimize the distance the game has to seek on the disc in order to load any given asset. A poorly optimized pak can easily have 30+ second load times on small rooms. There are two main things that are done in order to keep load times fast. | |||
* In world paks, assets are often duplicated so they appear multiple times within the pak; if an asset is used by a lot of different areas this can help reduce seek distance, but has the downside of bloating the total file size of the pak. To ensure the best balance between the two, asset duplication was likely flagged on a per-area basis, as large areas tend to have a lot of duplicate resources, while smaller ones that load quickly anyway don't. | |||
* Assets are generally grouped by load order - things that are used together are adjacent in the pak, and an asset's dependencies typically appear immediately preceding the asset itself. This grouping helps ensure that even when assets aren't duplicated the game will still be able to do just one large seek and then load a bunch of assets at once, instead of having to do a separate seek for each asset. | |||
For every asset loaded, the game checks every copy of the asset in the pak and loads whichever duplicate is the shortest distance from the last read position (the end of the last asset that was loaded). When loading an area, this is the order the game loads assets in: | |||
* First the game goes down the area dependency list in the [[MLVL (File Format)|MLVL]] file and loads every file in the list for every active layer. The game follows the exact order specified by the list. | |||
* After loading all area dependencies, the area itself is loaded. | |||
* Finally the game loads assets being used by the new area that are missing from the list. This primarily means [[SCAN (File Format)|SCAN]] files, the skybox model, and assets being used by PlayerActor animsets (this avoids loading PlayerActor assets for suits that the player doesn't have). If anything else is missing from the list, they will still be loaded, but this step will cause the game to hang until the load is finished. | |||
* Note that any assets that are already in memory will be skipped. | |||
'''Note:''' There are some discrepancies between the order assets appear in the pak and the actual load order specified by the MLVL file. There might be some more research needed to fully explain all the quirks behind Retro's pak optimization. | |||
== Tools == | == Tools == | ||