Two Bodies

Particles as listening matter: two forms shaped by sound finding each other.

An audio-reactive particle system built in Unity, with one piece of music as its only input: Ezio Bosso’s Rain in Your Black Eyes. Two particle bodies live on opposite sides of the screen, one listening to the bass of the strings, the other to the mids of the piano. The sound shapes their size, speed, and density moment to moment, while the song’s progress carries them toward each other, into an orbit, and finally into one form.

Role
Solo designer & developer
Context
Interaction Design, ArtCenter College of Design
Tools
Unity
C#
Particle System
VFX Graph

01 Concept

Can sound be translated into form?

I wanted form that grows, evolves and transforms across a whole piece of music, more than motion that simply reacts.

This sits inside a broader question I'm investigating: how do frequency, amplitude and rhythm shape the motion, scale and material qualities of digital forms?

Two bodies, two voicesOne body listens to the bass: the cello and strings. The other listens to the mids: the piano melody.
The song is the timelineWhere you are in the song decides how close the bodies are and what color they become.
Every mapping is a choiceBass drives expansion and treble drives flutter, because that is how those frequencies feel in the body.

The music shapes every moment.
I shaped the arc.

02 How It Works

256 frequency values, every frame.

Every frame, Unity takes a snapshot of the sound as 256 frequency values. That data is the raw material for everything on screen.

A three-part relationship

A purely reactive system loops: the same behavior repeats wherever you are in the song. Reading the song's progress gives the piece an arc.

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03 Process

From one system to two bodies.

I built the piece in layers: first particles that react to sound, then a timeline that gives the reaction an arc, then a split into two bodies with their own voices.

1 · AudioAn Audio Source plays the song, and a C# script samples its frequency data every frame.
2 · ReactionSmoothed amplitude drives emission, size, speed, and a color shift from cool blue to warm orange-red.
3 · TimelineSong progress moves the color through four phases: deep blue, violet, deep red, gold.
4 · Two bodiesThe biggest shift: one system became two, each with its own frequency range and color.
5 · Orbit and mergeVector3.Lerp eases them toward the center, into an orbit that speeds up as they get closer, and into one white-gold form.
6 · VFX GraphA GPU particle system for the merge, fed live audio values from the script.

VFX Graph for the merge

VFX Graph runs on the GPU and gives each particle its own logic. It appears only from 70% of the song, during the merge. Three exposed properties receive live values from the C# script every frame.

AmplitudeSpawn rate
BassParticle velocity
TrebleTurbulence, the flutter on piano notes

04 Feedback

What people saw in it.

“A cool fusion of authoring and procedural form.”

Professor

“So mesmerizing. A combination of art and music. This can become a piece that people can pay to watch and listen to.”

Classmates

05 What I Learned

Each parameter mapping is a design decision.

Sound has a feelLow frequencies are physical, expansive, gravitational. High frequencies are delicate and scattered. The mappings follow that.
Reaction needs a storyTying behavior to the song's progress turned a loop into a piece with a beginning and an end.
Designing behavior over timeWorking in a real-time engine meant designing how form behaves across a whole song, beyond how any single frame looks.

What's next

All on GPUMove both bodies into VFX Graph.
MaterialsUse Shader Graph so glow, transparency and iridescence react to frequency.
AttractorsPull particles toward target shapes authored by the music.
Other songsSee what forms different pieces of music produce with the same system.

Music: Rain in Your Black Eyes, Ezio Bosso