Asteroid

An oriented-bounding-box space rock for a 6-DOF shooter — a hitbox that tracks the rock's silhouette, shrinks as you shoot it, and kills anything that rams it.

What it does

AsteroidComponent is pure data: per-axis half-extents (hx/hy/hz) baked from the same seed the renderer stretches the procedural rock mesh with, so the box hugs the silhouette instead of a generous bounding sphere that would blow you up in empty space. radius is the mean radius (broad-phase culling + AI avoidance); the original* fields are the build-time size the live values shrink away from. AsteroidCollisionSystem runs two passes per frame. Bullets vs rock (priority 55, ahead of the generic bullet-impact pass): it sweep-samples each round into the rock's local frame, AABB-tests, and on a hit consumes the shot, emits bullet.hit, punches a surface ripple, imparts a tiny radius-scaled push + spin, shrinks the rock 1.5% of its original radius, and despawns it below 40% of original size. Ships vs rock: the ship is a sphere, so it grows each half-extent by the ship radius and point-tests — a rammer punches a big ripple and dies through the shared destroyShip path while the rock flies on. The impact ripple ring buffer is non-serializable visual state, so it lives in a System-side WeakMap keyed by the component, never on the pure-data component.

Use it in a scene

{
  "Asteroid1": {
    "tags": ["asteroid"],
    "components": {
      "Transform6DOF": { "x": 40, "y": 6, "z": 150 },
      "Asteroid": { "radius": 58, "hx": 59, "hy": 36, "hz": 80 },
      "Renderable": {
        "shape": "asteroid",
        "sx": 44, "sy": 44, "sz": 44,
        "r": 0.4, "g": 0.33, "b": 0.28,
        "meshSeed": 1337
      }
    }
  }
}

Props

• radius (number, default 10) — current mean radius; shrinks per bullet hit. Drives broad-phase culling and the shrink/despawn ratio.
• hx / hy / hz (number, each default = radius) — current OBB half-extents in the rock's local frame; all rescale in lockstep with radius.
• originalRadius (number, default = radius) — build-time reference; radius shrinks toward it and 40% of it is the despawn floor.
• originalHx / originalHy / originalHz (number, each default = the matching live extent) — build-time references; live extent = original * (radius / originalRadius).

Events

• Emits bullet.hit (BulletEvents.HIT, re-used from the Bullet component — Asteroid declares no events constant of its own) on each bullet-vs-rock contact — { shooterId, targetId, part: 'asteroid', partHp: 9999, x, y, z, dirX, dirY, dirZ }. This is the observer channel (hit-flash, SFX); the rock's shrink/despawn is applied inline, not routed through a Health event.
• Ships-vs-rock contacts route the rammer through the shared destroyShip helper (from the SpaceShooterHealth component), which owns its own kill/debris events — AsteroidCollisionSystem itself emits nothing extra there.
• Listens for nothing. Both passes are driven off entity queries, not the bus: asteroids are gathered by the asteroid tag, bullets by SpaceShooterBullet, and rammers by the system query.

Dependencies

• Transform6DOF — every asteroid needs one; its position + quaternion place the OBB and define its body axes.
• Renderable (shape: "asteroid" + a meshSeed) — draws the seeded rock whose stretch the half-extents mirror; seedless it degrades to a symmetric blob.
• SpaceShooterBullet + Velocity6DOF — the projectile the rock consumes; the System reads SpaceShooterBullet and the bullet's Transform6DOF/Velocity6DOF to sweep-test each shot (a rock's own Velocity6DOF is optional — only present rocks get the hit push/spin).
• SpaceShooterHealth + Parts — the ram pass queries [Transform6DOF, Parts] ships and kills them via destroyShip; SpaceShooterHealth also owns the debris pool the System registers on init.

Notes

• The asteroid tag is required. AsteroidCollisionSystem finds rocks with world.getEntitiesByTag('asteroid'), not by the AsteroidComponent alone — a rock carrying the component but missing the tag is invisible to every collision pass. This is the #1 gotcha.
• Hitbox and mesh scale are separate numbers: Renderable.sx/sy/sz size the drawn rock, Asteroid.hx/hy/hz are the collision half-extents. Keep them in the same proportion when hand-tuning or the box drifts off the silhouette.
• Shrink is per bullet: radius -= originalRadius * 0.015 (extents rescaled to radius / originalRadius each hit); the rock despawns once radius < originalRadius * 0.40. Want a durable rock? Give it a large originalRadius.
• Runtime state stays off the component — the ripple buffer lives in a System-side WeakMap, so serialize() round-trips cleanly with only the eight size numbers.