EnemySpawner

EnemySpawner

Pulses pooled enemies out from its own position on a timer, up to a live cap.

What it does

On a timer (interval) the spawner places a new enemy at its own world position, up to a per-spawner live cap (maxAlive). It never creates entities itself — it emits pool.spawn naming its pool, and the Pool blueprint hands out a reused (pooled) enemy. The cap stays a true live count by tracking the pool's pool.spawned / pool.released events (a release covers both a normal kill and the pool recycling an enemy under pressure). Per-spawn hp/speed/color ride along on the spawn event for games that apply overrides on acquire.

Use it in a scene

bjs download scene EnemySpawner

{
  "Spawner_NW": {
    "components": {
      "MeshPrimitive": {
        "primitive": "cylinder", "diameter": 1.6, "height": 0.4, "position": [-15, 0.2, 15],
        "material": { "diffuseColor": [0.6, 0.1, 0.15] }
      },
      "EnemySpawner": { "interval": 1.2, "maxAlive": 6, "pool": "enemy" }
    }
  },
  "Enemies": {
    "tags": ["enemy"],
    "components": {
      "Pool": { "size": 8, "name": "enemy" },
      "MeshPrimitive": { "primitive": "sphere", "diameter": 1.2, "material": { "diffuseColor": [0.85, 0.25, 0.35] } },
      "Enemy": { "arenaHalfWidth": 19, "arenaHalfDepth": 19 },
      "Health": { "hp": 2, "maxHp": 2 }
    }
  }
}

Props

• interval (number, default 1.2) — seconds between spawn pulses.
• maxAlive (number, default 6) — live cap for this spawner.
• pool (string, default "enemy") — name of the Pool blueprint to spawn from.
• enemyHp (number, default 2) — hp passed along on each spawn.
• enemySpeed (number, default 2.5) — speed passed along on each spawn.
• enemyColor ([r,g,b], default [0.85, 0.25, 0.35]) — color passed along on each spawn.
• enemyDiameter (number, default 1.2) — enemy diameter hint.

Events

• emits pool.spawn (with its pool, position, spawnerId, hp/speed/color).
• listens pool.spawned (bumps its live count) and pool.released (frees a slot).

Dependencies

MeshPrimitive — the spawner's own mesh, whose position is the spawn origin. Pool — the blueprint entity source; the spawner only requests spawns and counts them.

Notes

The live aliveIds set is non-serializable runtime state, kept in a WeakMap on the system rather than on the component. The scene must register a Pool blueprint under the same pool name (and that blueprint must carry Enemy + Health), or pool.spawn produces nothing.