Reference

Quality levels

Four tiers, from integrated laptop GPUs to 4K desktops. A tier sets the particle counts, the fog and reflection step counts, the shelter taps and the shadow map size.

const weather = await WeatherSystem.create({ renderer, scene, camera, quality: 'medium' });
weather.setQualityLevel('ultra');    // at runtime
weather.quality;                     // 'ultra'
QUALITY_LEVELS.high;                 // the settings object

#At a glance

Level	Rain streaks	Flakes	Splashes	Fog steps / scale	SSR steps	Shadow map	Shelter taps	Pixel ratio*
`low`	18k	9k	500	20 / 0.35	12	1024	4	1.0
`medium`	32k	16k	900	28 / 0.45	16	2048	6	1.25
`high`	55k	26k	1500	36 / 0.5	20	2048	8	1.5
`ultra`	90k	42k	2400	56 / 0.75	28	4096	12	2.0

* The pixel ratio is only applied with managePixelRatio: true. The demo applies it itself.

Particle counts are drawn at intensity 1. A drizzle at rain: 0.22 draws 22 % of them.

#Every field

Field	Used by
`rain`	`RainSystem`	Streaks at full rain (capped by `maxDrops`, 90000)
`snow`	`SnowSystem`	Flakes at full snow (capped by `maxFlakes`, 42000)
`splash`	`RainSystem`	Splashes at full rain (capped by `maxSplashes`, 2400)
`fogSteps`	`WeatherPipeline`	Volumetric fog raymarch steps
`fogScale`	`WeatherPipeline`	Fog buffer resolution relative to the drawing buffer
`ssrSteps`	`WeatherPipeline`	Puddle reflection ray steps
`shadowMapSize`	your `shadowLight`	Applied to the light passed to `setLighting({ shadowLight })`
`shelterTaps`	`SurfaceWeather`	Occlusion taps per pixel for dry-under-roof surfaces. `0` turns shelter off
`pixelRatio`	`renderer`	Recommended maximum pixel ratio

fogSteps, fogScale and ssrSteps only matter with weather.render(). Changing shelterTaps recompiles every patched material, so avoid switching tiers every frame.

#What it costs

Measured on an Apple M5 in headless Chromium at 1280 × 720, high, pixel ratio 1.5: 5.5–10 ms of GPU and CPU time per frame, depending on the preset. That's 100 fps or more; the demo itself runs at the 120 Hz cap. To measure your own machine, the dev helper node scripts/perf.mjs --quality high reports the frame cost per preset.

#Choosing a tier

Start at high. It's the default, and what the numbers above were measured on.
Test with full rain. downpour sets rain: 1, which draws every streak and splash the tier allows. Check your frame rate on it, not on clear.
Watch the pixel ratio. The scene pass, SSR and bloom run at the drawing-buffer size, and the fog at a fraction of it. On high-DPI screens, cap renderer.setPixelRatio() at the tier's pixelRatio, or pass managePixelRatio: true.
Adapt once, early. The demo measures its 2nd to 6th second and drops a tier below 30 fps. It's a simple pattern worth copying: see demo/main.js.

// the demo's tier switch
function setQuality(level) {
  weather.setQualityLevel(level);
  renderer.setPixelRatio(Math.min(devicePixelRatio, QUALITY_LEVELS[level].pixelRatio));
  renderer.setSize(innerWidth, innerHeight);
}