Modding Resources

As of r18964, the code base of 0AD attempts to deal with gatherable/tradable/tributable resources (ie. food, wood) in an agnostic fashion. In other words, the resources are not hardcoded inside simulation components, the GUI or the AI.

This means that adding or removing resources are somewhat easier for modders to do, should they wish. The following guide attempts to show how to do just that.

Please Note: The process of adding a resource, although a lot easier than before, is still not very modder friendly, particularly in the later sections, and you may get errors that might seem confusing. Please visit the 0ad-dev irc channel if you have questions (and please stick around long enough for an answer).

How to add a new resource to 0AD

1. Create a new file in the folder simulation/data/resources named something sensible (ie. water.json). If you like, copy one of the currently existing resources and amend as needed.

The contents of the file follow the following syntax:

{
    "code": "water",
    "name": "Water",
    "order": 1.1,
    "subtypes": {
        "well": "Well Water"
    },
    "truePrice": 50,
    "aiAnalysisInfluenceGroup": "ignore",
}

• code - Internal identifying code for this resource. Cannot be the same as another resource
• name - Player-friendly name of the resource. This will be localized into the player's chosen language (if localizing data exists for it)
• order - The order it appears in the in-game GUI. Resources will appear in numerical order of this attribute.
• subtypes - An object of Subtypes of this resource. At least one must be specified. The entries within this object follow the form "{subtype-code}": "{subtype-name}" where subtype-code is the internal reference to this subtype, and subtype-name is the user-friendly translatable name of the subtype. Resources can have the same subtype codes (ie. both wood and stone both possess a ruin subtype).
• truePrice - This is the true worth of the resource. This is used in calculating how much should be exchanged per click in the markets' Barter dialogue compared to other resources. See the Barter component for further details.
• aiAnalysisInfluenceGroup - This is used by the AI to help determine where to build resource deposit sites and where to allocate workers. There are three possible values:
  • ignore - The AI will ignore this resource when it comes to planning where to build gather sites. This could be for several reasons, for instance that supplies of this resource move around (ie. animals) or can be built by the player (ie. farms)
  • abundant - This resource is abundant (very common) on the average map, but each deposit only contains a small amount of the given resource. (ie. wood)
  • scarce - The resource has few deposits on the average map, but each deposit contains a fair to large quantity of the given resource. (ie. stone or metal)

2. Provide two icons, with names in the form of {res}.png and {res}_small.png (ie. water.png and water_small.png), and place them in the folder art/textures/ui/session/icons/resources. The icons should be 64x64 pixels and 16x16 pixels respectively.

3. Amend gui/common/setup_resources.xml so that you can use [icon=icon_{res}] in game UI texts. For example, adding the following to the file

       <icon name="icon_water"
           sprite="stretched:session/icons/resources/water_small.png"
           size="16 16"
       />
   

permits using [icon=icon_water] within the game's UI text.

Congratulations! Your new resource is now usable for tribute, loot or barter.

However! Starting a new game within 0AD will present

WARNING: Current GUI limits prevent displaying more than 4 resources in the top panel!

Displaying more resources within the session UI

Due to 0AD's requirement to support a minimum screen resolution of 1024x768px, there isn't really enough space in the top panel for more than four resources plus the population count. If you don't care about this, the easiest solution is to modify gui/session/top_panel/resources.xml line four to a number larger than 4, ie. <repeat count="5">. (A harder solution is to redesign the session UI. Good luck with that.)

Whilst the Trade and Diplomacy dialogs have a higher limit of displayable resources (at the time of writing: 8), once you build a market, you will find that selecting it will only display the first four resources. The easiest solution to this is to use a patch that moves the Barter options from the Barter panel into the Trade Dialog. You can find that patch in ticket #4366.

Gathering the new resource (in the normal way)

1. Supply at least two cursors: one that shows when you want a unit to return with a stack of resources, the others are used for tasking a unit to gather.

In 0AD, a cursor is comprised of two files: a .png and a .txt. The first is the actual image displayed on screen, whilst the second marks the co-ordinates that should be considered the "point" of the cursor. Both files are named almost identically with the only difference being their given extension.

The cursor used when tasking a unit to gather follows the pattern action-gather-{res}.{ext}. So to create a gather cursor for the water resource, the .png will be called action-gather-water.png, and the .txt action-gather-water.txt.

In a similar fashion, the cursor used when tasking a unit to return with their stack of the gathered resource follows the pattern action-return-{res}.{ext}.

All four new files should be placed within art/textures/cursors/. They'll get included by 0AD automagically.

You will also need to provide gather (but not return) icons for each of your resource's subtypes. These follow the same pattern as before: action-gather-{subtype}.{ext}. These can just be renamed copies of your action-gather-{res}.{ext} icon. (Remember you'll need both a .png and a .txt)

2. Provide something to gather from. For this you will need to create or modify an xml file to define the entity that will be your gather-site.

The parent template you may wish to inherit from will differ depending on your resource, for instance if your resource is something mined then inheriting from template_gaia_geo would be a good start, or if your resource comes from a plant then inherit from template_gaia_flora, or if gathered from some kind of structure (ie. a farm) template_structure_resource.

Either way, in order to make the gather-site provide your resource you must include the ResourceSupply component into the template of your gather-site:

  <ResourceSupply>
    <KillBeforeGather>false</KillBeforeGather>
    <Amount>Infinity</Amount>
    <Type>water.well</Type>
    <MaxGatherers>1</MaxGatherers>
  </ResourceSupply>

For the specifics of what tag does what here, see the schema of the ResourceSupply​ component.

3. To the templates of the units that will be doing the gathering (or the parent templates of those units), add a gather rate and carry capacity to the ResourceGatherer component. For example:

     <ResourceGatherer>
       <Rates>
         <water>1</water>
       </Rates>
       <Capacities>
         <water>10</water>
       </Capacities>
     </ResourceGatherer>
   

4. Your units will then need to drop the resource off somewhere. If the resource is to be dropped off at a structure (or worker elephant) that already permits resource dropping off, add your resource type to the existing Types list inside the ResourceDropsite component. Else add the component to the structure:

     <ResourceDropsite>
       <Types>water</Types>
       <Sharable>true</Sharable>
     </ResourceDropsite>
   

5. Lastly, modify the art/actor xml files of all the actors of all the units you wish to gather this new resource so as to tell the game which animations and props to use on units for gathering and returning with your new resource. Every civ that has that unit, every promotion level. The easiest way to do this is to use variants (see the contents of the art/variants folder for some idea of how this works), but it will still require modifying a lot of actor templates.

This step could be seen as optional, as the gathering will still take place without error, but without it units will just stand at the resource (playing the idle animation) until their resource capacity is full.

To remove a resource

In short, follow the instructions to add a resource, but in reverse making sure to remove all reference to the resource.

Known Issues or Problems

• The session gui is limited to displaying four resources (plus population count) in the top bar.
• Unless the patch that relocate the Barter icons to the Trade Dialog is applied, the session gui is limited to displaying four resources for Barter purposes.
• Modifying countless actor files to add animations and props is not very mod-friendly.
• Modders may wish to restrict the ability to barter, trade, or tribute resources. This is not currently implemented, see #4370.