A real-time physics simulator for tuning a marble-machine snare drum trigger, built with Rust, Bevy 0.18, and Rapier. Runs natively on desktop or in the browser via WebAssembly.

MM3Sim models the classic Wintergatan Marble Machine trigger mechanism: two steel marbles are released simultaneously toward a snare drum head. Your task is to tune the chute geometry so both marbles arrive at exactly the same time (Δt = 0 ms) with maximum consistency across repeated runs.

cargo run

rustup target add wasm32-unknown-unknown
cargo install trunk
trunk serve --open

Two steel marbles are released at the same time:

All panels can be toggled by clicking their title bars.

Shows live marble velocities, per-run impact data, and aggregate summary statistics. Key features:

• Live marbles — Current speed, vertical velocity, horizontal speed, angle of attack, and spin for each marble in flight
• Per-run stats — For each complete run, view flight time, impact speed, AoA, kinetic energy, vx/vy/vz components, spin rate, arm angle, and hit location
• Summary statistics — Mean ± std deviation across all complete runs, with min/max range for Δt only

Use Expand All / Collapse All, Reset, or individual run checkboxes to manage large datasets. Click the Vib dropdown in Stats to switch to vibraphone mode (see below).

Controls the chute Bézier curve:

• Adjust P0, CP1, CP2, and P3 coordinates numerically
• Toggle handle visibility with checkboxes
• Enable Straight line mode to create a pure ramp (all handles collapse onto P0–P3 line)
• Drag control-point spheres directly in 3D for intuitive curve editing

Comprehensive reference including:

• Keyboard controls and camera navigation
• Physics model details
• Statistics glossary with formulas
• Tuning guide and tips
• Chute editor instructions
• Graph interpretation

Open per run via the Graph button in any run entry. Each graph shows:

Multiple graphs can be open simultaneously. Close via the × button or toggle in run entry.

3D orientation overlay showing X/Y/Z axes for spatial reference.

Click the Vib dropdown in the Stats panel to switch from snare mode:

• Each run selects one of 37 vibraphone bars (F3 through E5, spanning two octaves)
• Hit location on the drum determines which note plays via a physical node system
• Default pattern transcribed from Wintergatan's Marble Machine MusicXML score
• Experiment with melodic triggers by adjusting chute geometry

The reference flight time is 450 ms (theoretical 1 m free-fall). The Δt statistic shows chute_fly_time − 450 ms. To achieve a perfect trigger:

1. Click to spawn marble pairs
2. Watch the Summary section — target mean Δt of 0 ± a few ms
3. Adjust chute handles until both marbles arrive simultaneously
4. Reduce standard deviation (σ) for consistent triggers across runs

Use Straight line mode as a starting point, then sculpt with Bézier handles for fine control.

src/
├── components/
│   ├── chute.rs        — Bézier mesh with adaptive tessellation
│   └── snare.rs        — Snare drum with counterweighted pivot arm
├── resources/
│   ├── constants.rs    — Physical and visual constants
│   ├── chute_params.rs — Bézier control points and editor state
│   ├── vibraphone_params.rs — Vibraphone bar configuration
│   └── marble_runs.rs  — Per-run data model (HitRecord, RunHistory)
├── systems/
│   ├── setup.rs        — Scene initialization
│   ├── camera.rs       — Orbit/pan/zoom controls
│   ├── chute_editor.rs — Parameters UI + curve rebuild
│   ├── chute_handles.rs — Handle sphere picking and dragging
│   ├── hud.rs          — Stats panel, help panel, summary statistics
│   ├── instrument.rs   — Snare/vibraphone instruments
│   ├── marble_graph.rs — Per-run velocity graph rendering
│   ├── marble.rs       — Spawning, trails, impact data collection
│   ├── programming_wheel.rs — Song programming interface
│   ├── axes.rs         — 3D axis orientation widget
│   └── sound.rs        — Impact sound synthesis (WAV/Web Audio)
├── main.rs             — Application entry point
└── Trunk.toml          — WASM build configuration

The chute is a cubic Bézier curve in the Y–Z plane (height × depth). Coordinates are relative to the snare top-face centre.

Enable Straight line mode to create a pure ramp by collapsing CP1/CP2 onto the P0–P3 line. Drag handle spheres directly in 3D for intuitive curve editing.

All objects use Rapier3D rigid-body physics:

MIT License — see LICENSE for details.

Based on the Wintergatan Marble Machine design. The vibraphone mode uses notes from the original MusicXML score.