Faction and allegiances in Developer Help

ID:154753
 
Dec 30 2011, 9:06 pm
I'm trying to create a faction system of sorts for my roguelike and I'm not quite sure how to go about making it work the way I envisioned it. Here is a scenario:

Skeletons and rats would be their own group. They would not attack each other. Skeletons and rats will attack goblins though.

Guards will attack any sort of monster. Guards will not attack players, unless players attack guards.

Turtles do their own thing. No one would really bother to attack turtles.

Basically I'd need to be able to easily define different groups and add/remove allegiances so groups will attack/ignore each other.
#1 Dec 31 2011, 8:09 am
This is essentially two questions mixed together. One is relatively easy - "How do I model the concept of monsters belonging to a 'faction', and factions having opinions about other factions?'. You could, for example, give monsters a textual faction tag, and use it as a key for an associative list containing faction datums, which are an associative list of other faction names and value representing how friendly the faction is with the other faction.

var/const
    FACTION_HOSTILE = 0
    FACTION_FRIENDLY = 1
    FACTION_NEUTRAL = 2

    FACTION_DEFAULT = FACTION_NEUTRAL

faction
    var/list/faction_rels = list()

    proc
        get_relation(other_fac)
            if (faction_rels[other_fac] == NULL) return FACTION_DEFAULT
            return faction_rels[other_fac]

var/list/faction_list = list()
proc/get_faction(faction)
    return faction_list[faction]

mob
    var/faction

    proc/check_relation(mob/other)
        var/faction/f = get_faction(faction)
        if (!f) return FACTION_DEFAULT
        return f.get_relation(other.faction)


The second, more complicated question is about how to model AI that uses this information. That depends entirely on how complex your game is and how you want to run things. This DreamMakers article contains a discussion about a state-machine based approach to AI that might be worth considering.
#2 Dec 31 2011, 1:03 pm
In response to Jp (#1)
I see. Thank you. I've never really used associative lists before. Would this example be the right way based on what you posted?

var/list/faction_list = list(/faction/player = "the_player", /faction/undead_vermin = "skeletons_and_rats")

faction
    player

    undead_vermin
        faction_rels = list(/faction/player = FACTION_HOSTILE)

mob
    player
        faction = "the_player"

    enemy
        rat
            faction = "skeletons_and_rats"

        skeleton
            faction = "skeletons_and_rats"
#3 Dec 31 2011, 11:55 pm
In response to LordAndrew (#2)
Not quite. You're associating types with strings, not instances of the datum, and you've got them the wrong way around.

More something like this:

faction
    player
        faction_rels = list("undead_vermin" = FACTION_HOSTILE)

    undead_vermin
        faction_rels = list("player" = FACTION_HOSTILE, "undead_vermin" = FACTION_FRIENDLY)

var/list/faction_list = list("player" = new /faction/player, "undead_vermin" = new /faction/undead_vermin)

mob
    player
        faction = "player"

    enemy
        rat
            faction = "undead_vermin"

        skeleton
            faction = "undead_vermin"


Obviously doesn't solve the AI problem, but part of the solution. Also, untested.

I'd recommend reading the reference entry on associative lists and playing around with them a bit - they're /very/ useful.
#4 Jan 1 2012, 12:00 am
In response to Jp (#3)
OH. Wow, haha. Thank you again Jp, and I will make sure to have a look at the reference.