Gameable Engine

Talk to a character ​

Goal ​

A talking character (an AI NPC on Convorcher) the player walks up to, presses E at and talks to in their own words, typed or spoken, while the character answers aloud with subtitles and a moving face; the game hears what was said and how the story is going. Needs Set up talking characters and Write a character's story.

Files you will edit ​

  • src/systems/talk.ts
  • src/game.ts

Steps ​

  1. The talk system. src/systems/talk.ts holds the character's prefab (tagged Talks, not Npc, so the scripted dialogue leaves it alone), starts the talk on E within reach, asks what the player says, and ends the talk when they walk away.

    ts
    import { Transform, conversation, prefab, query, type GameContext } from 'gameable';

import { NPC_HALF_HEIGHT, NPC_RADIUS } from '../prefabs';

/**
 * Tag: this NPC talks through the conversation service. Define it once: tags are matched by reference, so a second
 * `Talks` (one in `src/prefabs.ts` too) makes the query below find nobody. Import this one everywhere else.
 */
export const Talks: Record<string, never> = {};

/** The guard: `char.guard` is its character asset, `guard` its story (`src/guard.story.yaml`). */
export const GuardPrefab = prefab({
  name: 'guard',
  body: {
    shape: 'capsule',
    dims: [NPC_RADIUS, NPC_HALF_HEIGHT],
    // kinematic, not `character`: two character controllers slide through each other
    kind: 'kinematic',
    mass: 70,
    layer: { character: true },
    mask: { defaultLayer: true, staticGeometry: true, player: true, character: true },
  },
  character: 'char.guard',
  components: [Talks],
});

const TALK_ID = 'guard';
const REACH = 2.2;
export const talkState = { npc: 0, open: false, lastRevision: -1 };

export function talkSystem(ctx: GameContext): void {
  for (const event of ctx.events) {
    if (event.tag !== 'conversation-event' || event.val.entity !== talkState.npc) continue;
    const { kind, text } = event.val;
    if (kind === 'input' && talkState.open)
      conversation.command(talkState.npc, 'ask', TALK_ID, text);
    else if (kind === 'story') {
      const story = conversation.story(text);
      if (story && story.revision > talkState.lastRevision)
        talkState.lastRevision = story.revision;
    } else if (kind === 'error' && text.startsWith('closed:')) talkState.open = false;
  }
  if (ctx.player === 0) return;
  for (const npc of query(ctx.world, [Talks])) {
    const near = distance(ctx.player, npc) < REACH;
    if (!talkState.open && near && ctx.input.pressed('E')) {
      talkState.npc = npc;
      talkState.open = true;
      talkState.lastRevision = -1;
      conversation.command(npc, 'start', TALK_ID);
    } else if (talkState.open && npc === talkState.npc && !near) {
      talkState.open = false;
      conversation.command(npc, 'end', TALK_ID);
    }
  }
}

function distance(a: number, b: number): number {
  return Math.hypot(
    (Transform.x[a] ?? 0) - (Transform.x[b] ?? 0),
    (Transform.z[a] ?? 0) - (Transform.z[b] ?? 0),
  );
}

    An error that starts with retry: keeps the talk open: the player just asks again. It is the service's fault, never the player's. For an E: talk prompt, show it from src/hud.ts when talkState.open is false and the player is in reach.

  2. Put them in the game. In src/game.ts, add talkSystem to systems and the guard to spawns:

    ts
    spawns: [place(GuardPrefab, { position: [0, 0, 4], yaw: Math.PI }, NPC_CENTRE) /* , ... */],
systems: [/* ... */ talkSystem],

Verify ​

  • Walk to the guard and press E: the talk box opens at the bottom of the page.
  • Type "I need to get to my mother's farm": the guard answers aloud, the subtitle shows it and the face moves.
  • A story event follows the reply, with gave-reason in completedObjectives once you have said why.
  • Walk away: the talk box closes.

Going further ​

See also ​