Move your pointer, or tap, to move the listener
Ray-traced sound propagation for Unity + FMOD
Sound that knows where the walls are.
Wavetracing casts rays from every sound source. They bounce off walls, leak through thin doors, get muffled by rock and find their way around corners. What reaches each listener drives your FMOD events, live.
Coming to the Unity Asset Store in early 2027 · wavetracing.marketing@slowburn-studios.com
The modules
Stack only what a sound needs.
Each sound source gets a list of modules. A drip needs two, a monster needs six. Every demo below runs a simplified 2D version of the engine live in your browser; the real one is 3D, runs in Unity and drives FMOD. Turn on sound in the top right to hear the mix.
Drag the ember listener. Turn penetration off and only the bounce paths are left.
Why not just raycast to the player?
One ray says blocked or clear. Sound doesn't work like that.
The quick fix is a single line-of-sight check. It works until a pillar edge cuts the sound dead, or a sound comes through a doorway and the check says it's behind a wall. Drag the listener on either side and watch the two gain curves.
single raycast: on or off, a hard cut at every pillar edge. Wavetracing: fades as paths are lost, and comes back through the doorway.
Use cases
Built for a horror game. Useful for any game where you listen.
Wavetracing grew out of a small horror game set in a mine, where hearing where things are is the whole game. These are the setups it was tuned on.
The wall-mounted radio
A cone-shaped speaker you can step behind. Behind it you still hear something through the leak and the bounces, just quieter and softer.
EmissionPropagation Try it →A voice behind the rockfall
Muffled, strained, clearly behind something. Swing the pickaxe and she is suddenly bright and close, in the same frame.
MaterialsTransmission Try it →The stalking monster
Walls block absolutely, so doorways matter. The AI gets an event when you lose track of it, and the music gets one when it finds you.
LifecycleSpatialization Try it →The cavern that answers
A line of dialogue comes back once from the far wall over a long, slow wash. The echo comes from real geometry, stretched for drama.
ReverbEcho Try it →Which door is it behind?
The sound pans from the doorway it pours through, not through the concrete. Direction becomes something the player can act on.
Spatialization Try it →Thirty drips, one budget
One shared config, distance tiers and culling. Twenty-five of them sleep while you stand at the other end of the gallery.
Performance Try it →In Unity
Add a component. See the rays. Hear the difference.
No baking
Rays are cast live. Move a wall, break a rockfall, open a door, and the sound follows in the same frame.
No colliders on the listener
Detection is analytic. Put an AudioConsumer on the camera and you are done.
See what you hear
Select a producer in play mode and its rays draw in the Scene view, so you debug with your eyes.
Modules you stack
Each producer config is a list of modules. Leave out what a sound does not need, and it costs nothing.
Drives the FMOD events you already have
- Gaincoverage-scaled path average
- Low-pass / high-passfrom penetration depth
- Parametric EQup to 5 bands from materials
- Distortionbounces, walls, rusty metal
- Reverbwet, decay, diffusion, density
- Echoone tap from real geometry
- 3D positiona virtual source at the doorway
- Directional focuspoint image or wraparound
- Delayenergy-weighted path length
- Spread & chorushow diffuse the arrivals are
Everything arrives as event parameters or Core DSP units on the event's own chain, so sound designers stay in FMOD Studio.
Coming to the Unity Asset Store in early 2027.
Built by one developer at Slowburn Studios. If you want early access, have a level that sounds wrong, or you're just curious, write to me.
Requires FMOD for Unity. Unity 6.