Lightning and thunder

#Automatic strikes

weather.set({ lightning: 0.5 });   // 0 = manual strikes only, 1 = a storm

lightning (0–1) is the strike frequency. Above 0.05, strikes fire automatically. The gap between them is lerp(22, 2.5, lightning) seconds, randomised ×0.4 to ×1.6: about every 22 s at the low end and every 2.5 s at 1. thunderstorm uses 0.85. Loading a preset with lightning > 0 arms the first strike 1.5 s later, so a storm starts promptly.

Lightning also raises state.cloud to at least state.lightning.

#Strike on demand

weather.strike();                                         // random, roughly ahead of the camera
weather.strike({ distance: 150 });                        // random direction, 150 m away
weather.strike({ position: new THREE.Vector3(80, 0, -200) });   // this ground point

Without a position, the bolt lands 110–370 m from the camera (lightning.minDistance / maxDistance), within about ±46° of where the camera faces. Its top is 85–125 m above the ground point. strike() works at any lightning value, including 0.

#Events

const off = weather.on('strike', e => {
  console.log(`strike ${e.distance.toFixed(0)} m away, thunder in ${e.delay.toFixed(1)} s`);
});
weather.on('thunder', e => shakeCamera(120 / e.distance));   // when the sound arrives
off();                                                       // unsubscribe

Both events carry the same StrikeEvent:

'strike' fires immediately. 'thunder' fires delay seconds later, from inside update().

#The flash

Each strike is four pulses over about half a second: full strength, then 0.55, 0.85 and a random last one, each decaying fast. The flash ends 1.5 s after the strike.

The flash also lights the rain and snow, and in weather.render() it lights the fog volume around the bolt.

#Flash your own lights

Pass lights: false to create() if you'd rather light the scene yourself. Then read flash every frame:

const weather = await WeatherSystem.create({ renderer, scene, camera, lights: false });

renderer.setAnimationLoop(() => {
  weather.update(dt);
  stormLight.intensity = weather.lightning.flash * 5;
  skyMaterial.uniforms.flash.value = weather.lightning.flash;   // light your own clouds
  weather.render();
});

The demo sky does exactly this with sky.setFlash(weather.lightning.flash, weather.lightning.flashDirection).

#Thunder

Thunder audio is synthesized noise, low-passed more for distant strikes, and quieter with distance. It needs a user gesture before the browser will play it:

button.addEventListener('click', () => weather.audio.unmute());
weather.audio.volume = 0.5;   // master volume, default 0.7
weather.audio.mute();

The same WeatherAudio plays the rain hiss and the gusting wind. It's muted by default.