flutter3d_audio 0.4.0

Positional audio for flutter3d: attenuation, panning and voice limiting, with a pluggable backend.

flutter3d_audio

Positional audio: attenuation, panning, occlusion and voice limiting, with a pluggable backend. A sibling of flutter3d_game rather than a RenderPlugin — it draws nothing, so the renderer's plugin seam does not apply to it.

Depends on neither flutter3d nor flutter_gpu. It is handed a listener pose and emitter positions; where those come from is the application's business.

Why the geometry is computed here

SoLoud has a 3D layer, and it cannot be used for anything that moves. Applying a moved source or a turned listener requires update3dAudio(), and flutter_soloud 4.1.7 exposes neither that call nor anything that makes it: its set3dSourcePosition passes straight through to a SoLoud method that only marks the source dirty. A source set once at play3d never moves again, and in a first-person game the listener turns constantly.

So AudioScene computes gain and pan, and the backend is asked only for a flat voice with a volume and a pan — which every backend can do and which takes effect immediately. If a later flutter_soloud exposes the call, the right change is a second backend, not an edit to this one.

Shape

final scene = AudioScene(
  backend: SoLoudBackend()..open(),
  maxVoices: 24,
  // The walls belong to the physics; this package must not learn about them.
  occlusion: (from, to) => world.raycast(from, to) ? 0.3 : 1.0,
);

await scene.preload(<SoundDef>[Sounds.pistol, Sounds.door]);

scene.play(Sounds.pistol, muzzlePosition);          // one-shot
final hum = scene.play(Sounds.torch, torchPosition); // holds a looping emitter

// Once a frame, after everything has moved.
listener.aimAt(eyePosition, yaw);
scene.update(listener);

An emitter is returned so whatever owns a moving source can move it; the mixer updates that voice rather than restarting it.

What the mixer decides

• Attenuation — InverseRolloff by default, the only one of the three that sounds right when the player walks past something. LinearRolloff and ExponentialRolloff are there because designers ask for them, and NoAttenuation for music.
• Panning — the left-right component of the direction, and nothing else. Yaw only: tilting your head back does not swap left and right.
• Voice limiting — priority first, loudness second. A door closing outranks the ninth footstep even when the footstep is nearer.
• Instance limiting — ten identical grunts on one frame are a click, not ten times as loud.

Testing

SilentBackend records every call and makes no sound, so the whole mix is testable without an audio device — and it is what a headless build or a player who has turned sound off should use, rather than a branch at every call site.

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Part of flutter3d, an independent implementation of a 3D engine for Flutter — not a fork or a binding of another engine, and not affiliated with the Flutter team. Three switchable rendering backends: Impeller via Flutter GPU, WebGL2, and a software rasteriser. glTF, OBJ and .f3d loading, six lighting models, shadows, bloom, skinning, animation, BVH culling and picking; a deterministic fixed-step game layer with collision, navigation, positional audio, and gamepad and touch input. Three example games — shooter, platformer, racing — each built on its genre package: flutter3d_game_shooter, flutter3d_game_platformer, flutter3d_game_racing. A new game starts from apps/flutter3d_template_app. Documentation: https://flutter3d.pleion.dev.