A physics-accurate flight simulator running entirely in the browser via WebAssembly. Built with Rust, Bevy 0.18, and Avian3D — no backend, no install, just open and fly.

This project ports a research-grade aerodynamic flight model (Khan & Nahon 2015) into a real-time 3D simulator with procedurally generated infinite terrain, streamed at runtime. Everything — physics, terrain, rendering, navigation — runs at 60 Hz in a WASM bundle served as a static site.

Tech stack: Rust · Bevy 0.18 (ECS game engine) · Avian3D (rigid-body physics) · bevy_egui (debug UI) · Trunk (WASM bundler) · Perlin noise terrain

The aerodynamic model is based on the Khan & Nahon 2015 academic paper, implemented surface-by-surface:

• Control surfaces — Wings, ailerons, elevator, rudder, and flaps are each independent physics components. Each surface computes lift and drag in its local chord plane using a full lift curve with configurable stall angles, then rotates forces into world space.
• Ground effect — A Gaussian proximity model increases effective wing aspect ratio near the ground, realistically boosting lift and reducing induced drag on landing and takeoff.
• Trapezoidal velocity prediction — A midpoint-accurate integrator improves numerical stability at low framerates.
• Fixed-pitch propeller — Thrust scales with a realistic RPM→thrust curve. A mixture control adjusts fuel-air ratio; pulling it to idle cutoff kills the engine.
• Engine state machine — Off → Cranking (starter key) → Running. Engine responds to throttle and mixture.
• Servo lag — All control inputs filter through a tunable time constant, preventing instantaneous surface deflection.
• Fuselage drag — Body-axis-aligned form drag models realistic high-AoA and crosswind behavior.
• Rotational damping — Per-axis damping stabilizes pitch, roll, and yaw.
• Landing gear — Three spring-damper struts (nose + two mains) sampled against terrain height. Tyre friction applies strong sideways resistance and light rolling resistance, generating correct pitch moments about CoM on ground.

All flight model constants are live-editable at runtime from the debug panel — no recompile needed to tune.

An infinite, seeded world generated from multi-octave Perlin noise:

• Biome climate system — Continentalness, temperature, and humidity fields combine to produce deserts, grasslands, taiga, forests, snowy peaks, and ocean. Biome colors are painted as vertex colors on the terrain mesh.
• Lapse-rate temperature — Temperature drops with altitude, producing natural snow lines on peaks.
• Latitude banding — Warm equator strips and cold polar bands shape the climate map.
• Deterministic — The same seed always produces the same world. Fully reproducible.

The world is divided into 500 m × 500 m chunks, loaded and unloaded around the camera in real time:

• LOD system — Four distance bands with 12→8→3→1 mesh subdivisions from near to far.
• Rate-limited generation — At most 3 chunks spawn per frame to prevent WASM main-thread stalls.
• Async mesh baking — Mesh construction runs on the AsyncComputeTaskPool; on WASM this is carefully throttled to the main thread.
• Chunk boundary tracking — The grid only re-scans when the camera crosses a chunk edge, keeping overhead near zero between moves.
• Render distance — 28-chunk radius (~6 km), despawning chunks outside the window.

Airports are placed on an infinite 5 km grid, each cell seeded deterministically:

• Five airport classes — Dirt strips, small GA, large commuter, regional, and hub airports, distributed by cell hash.
• Terrain flattening — Terrain under each runway is flattened in an oriented rectangle and ramps smoothly back to natural height.
• Runway lights — Strobes, beacons, and approach lights animate based on engine and time-of-day state.
• Runway identifiers — Deterministic ICAO-style identifiers generated from world position.
• Waypoint labels — 3D stalk markers at runway positions with projected screen labels showing ident, airport name, and distance. Labels fade at range (visible 3–120 km).

• Dual-camera pipeline — An inner Camera3d renders the 3D world to a 640×360 render texture. An outer Camera2d upscales it to the window with integer pixel scaling, giving a clean retro aesthetic.
• Day-night cycle — Orbiting sun directional light with a 2,500-star procedural starfield and a rendered sun disc.
• Atmospheric fog — Distance fog with configurable base color, extinction, and inscattering. Sun-glow tinting blends with the directional light.
• Ocean — A single low-poly water plane at sea level follows the camera horizontally with a tunable PBR material.
• Aircraft exterior lights — Nav lights (red/green/white), strobes, belly beacon (pulses with engine), and a toggled landing light spotlight.
• Low-poly aircraft — GLTF Cessna 172 with animated propeller (angular velocity matches engine RPM).
• Physics interpolation — TransformInterpolation smooths the aircraft visually between fixed 60 Hz physics steps.

Two modes, toggled with F:

• Orbit camera (default) — Follows the aircraft at 15 m radius. Arrow keys adjust pitch/yaw of the orbit angle.
• Free camera — WASD/QE movement at 5 m/s normal, 300 m/s with Shift, 2,000 m/s with double-Shift. Arrow keys look.

A full live-tuning system for iteration without recompiling:

• F3 debug panel — egui sliders for every physics constant: aero surface configs, weight & balance (fuel, cargo, occupants shift CoM and inertia live), engine/propeller params, servo response, gravity, air density, terrain generation (seed, scales, LOD), sky, water, fog, lights, and map display.
• F4 map overlay — 256×256 rendered world map with biome/height/category view tabs, aircraft and camera markers, airport overlays with runway lines, a 10-minute breadcrumb trail, click-to-select airports with Direct-To course line, and scroll/drag pan+zoom.
• HUD — Top-left text overlay: speed (m/s and knots), altitude, engine state, mixture, throttle, flaps, RPM, FPS.
• G gizmos — 3D wireframe overlays for CoM, velocity, thrust, gravity, landing gear struts, and per-surface aerodynamic force vectors.

The project uses Bevy's ECS (Entity-Component-System) throughout. Each aircraft subsystem is a plugin:

Physics runs at a fixed 60 Hz (PhysicsSchedule) decoupled from render framerate. Custom force systems (apply_aero_forces, apply_landing_gear) register before the broad-phase collision pass.

Requires Rust and Trunk:

trunk serve          # dev server with hot reload
trunk build --release  # optimized WASM bundle → dist/

The dist/ directory is a self-contained static site — drop it on any static host.

• Khan, W. & Nahon, M. (2015). Real-time modeling of agile fixed-wing UAV aerodynamics. — basis for the aerodynamic surface model
• Low-poly Cessna 172 model — CC-licensed GLTF asset (assets/low-poly-airplane/)