OXP howto
An Oolite Expansion Pack can cause many big changes or additions to Oolite's gameplay, or it may represent just a small, subtle alteration. By appearances, there is no way to tell what is inside, as it's merely a folder with the added extention .oxp. Inside, it will at least contain a folder named Config, and possibly other folders such as AIs, Models, Textures, Sounds, etc. It is down to the goal of the OXP, which ways to combine elements to the OXP's contents.
Contents
AIs
The folder named AIs contains any AI.plist additions the OXP might use.
Config
This folder contains Property lists such as:
- shipdata.plist that introduces any new entity (ships, stations, objects etc.) to Oolite.
- shipdata-overrides.plist that selectively can replace shipentries in other shipdata.plists
- shipyard.plist that introduces new ships available for player purchase.
- shipyard-overrides.plist that selectively can replace shipentries in other shipyard.plists
- script.plist to handle conditional script actions. Note that script.js will be loaded in preference to script.plist if both exist. (script.oos was briefly introduced during 1.70 development but is now depracated in favour of JS.)
- planetinfo.plist that plots system specific changes from the default. May also contain script actions.
- commodities.plist that contains information for each commodity in a market.
- demoships.plist that selects demoships to show on startup.
- descriptions.plist that adds vocabulary to Oolite texts.
- hud.plist that allows for changes or a radically new Head-Up Display.
- characters.plist that adds non-player characters to Oolite.
- equipment.plist lists upgrades available from the Shipyard.
- pirate-victim-roles.plist that defines which roles should act as traders.
- missiontext.plist, speech_pronunciation_guide.plist are some of the other custom methods.
All plist files except for those introducing new AI, belong in Config.
In its simplest form, an OXP could contain only a Config with an altering script.plist or planetinfo.plist. An OXP that adds a new ship needs a shipdata.plist entry, and unless it is based entirely on existing Oolite data, would include a model and texture.
Models
Oolite models need to be in the .dat format. There are utilities available that convert models made in Wings 3D (.obj) and Meshwork (.mesh) into this. A .dat file can be opened in a plain text editor to view the object's assigned texture names and see that they correspond with the actual file names in the Textures folder. The .dat file must be named exactly as it is referenced in the shipdata model entry.
Textures
Oolite's textures are in the .png format, usually at a standard 1024x1024 size, and must be named exactly as they are named in the .dat file.
Requires
Every oxp should contain a Property lists with the name requires.plist that is placed at the main level of the oxp folder. It contains just a dictionary with two entries: version and max_version. version is the lowest Oolite version the code can run on. This ensures that older Oolite versions don't behave bad or crash because they load an oxp that does contain unknown stuff. The max_version is only needed when you want an oxp to not run with newer Oolite versions. Very useful for adding in test versions of an oxp to ensure this test version is not used forever.
A preview of things to come
The scripting environment is being reworked to use JavaScript as the core scripting language. See Scripting Oolite with JavaScript for more information.
