Rulesets Overview

Quickstart

Rulesets allow modifiable sets of data for units, advances, terrain, improvements, wonders, nations, cities, governments, and miscellaneous game rules, without requiring recompilation, in a way which is consistent across a network and through savegames.

  • To play Freeciv21 normally: do not do anything special. The new features all have defaults which give the standard Freeciv21 behavior.

  • To play a game with rules more like Civ1, start the server with:

$ freeciv21-server -r data/civ1.serv

and any other command-line arguments you normally use, depending on how you have Freeciv21 installed you may have to give the installed data directory path instead of data.

Start the game normally. The game must be network-compatible to the server (usually meaning the same or similar version), but otherwise nothing special is needed. However, some third-party rulesets may potentially require special graphics to work properly, in which case the game should have those graphics available and be started with an appropriate --tiles argument.

Note that the Freeciv21 AI might not play as well with rules other than standard Freeciv21 Classic or Civ2Civ3 rulesets. The AI is supposed to understand and utilize all sane rules variations, so please report any AI failures so that they can be fixed.

The rest of this file contains:

  • More detailed information on creating and using custom/mixed rulesets.

  • Information on implementation, and notes for further development.

Using and Modifying Rulesets

Rulesets are specified using the server command rulesetdir. The command line example given above just reads a file which uses this command (as well as a few of the standard server options). The server command specifies in which directory the ruleset files are to be found.

The ruleset files in the data directory are user-editable, so you can modify them to create modified or custom rulesets (without having to recompile Freeciv21). It is suggested that you do not edit the existing files in the “civ2civ3”, “classic”, “experimental”, “multiplayer”, “civ1”, or “civ2” directories, but rather copy them to another directory and edit the copies. This is so that its clear when you are using modified rules and not the standard ones.

The format used in the ruleset files should be fairly self-explanatory. A few points:

  • The files are not all independent, since e.g., units depend on advances specified in the techs file.

  • Units have a field, “roles”, which is like “flags”, but determines which units are used in various circumstances of the game (rather than intrinsic properties of the unit). See comments in common/unit.h

  • Rulesets must be in UTF-8. Translatable texts should be American English ASCII.

Restrictions and Limitations

  • units.ruleset :

Restrictions:

  • At least one unit with role “FirstBuild” must be available from the start (i.e., tech_req = “None”).

  • There must be units for these roles:

    • “Explorer”

    • “FerryBoat” (Must be able to move at sea)

    • “Hut” (Must be able to move on land)

    • “Barbarian” (Must be able to move on land)

    • “BarbarianLeader” (Must be able to move on land)

    • “BarbarianBuild” (Must be able to move on land)

    • “BarbarianBoat” (Must be able to move at sea)

    • “BarbarianSea”

  • nations.ruleset :

Restrictions:

  • Government used during revolution cannot be used as default_government or init_government for any nation.

Implementation Details

This section and following section will be mainly of interest to developers who are familiar with the Freeciv21 source code.

Rulesets are mainly implemented in the server. The server reads the files and then sends information to the game. Rulesets are used to fill in the basic data tables on units etc., but in some cases some extra information is required.

For units and advances, all information regarding each unit or advance is now captured in the data tables, and these are now “fully customizable”, with the old enumeration types completely removed.

Game Settings Defined In The Ruleset

Game settings can be defined in the section [settings] of the file game.ruleset. The name key is equal to the setting name as listed by ‘show all’. If the setting should be locked by the ruleset, the last column should be set to TRUE.

set =
  { "name", "value", "lock"
    "bool_set", TRUE, FALSE
    "int_set", 123, FALSE
    "str_set", "test", FALSE
  }

Scenario Capabilities

Some scenarios can be unlocked from a ruleset, meaning that they are not meant to be used with strictly one ruleset only. To control that such a scenario file and a ruleset are compatible, capabilities are used. Scenario file lists capabilities it requires from the ruleset, and ruleset lists capabilities it provides.

Some standard capabilities are:

  • std-terrains: Ruleset provides at least terrain types Inaccessible, Lake, Ocean, Deep Ocean, Glacier, Desert, Forest, Grassland, Hills, Jungle, Mountains, Plains, Swamp, Tundra. Ruleset provides River extra