blender-weather-fx

1# Weather FX
2 
3The execution model is in `blender-core`. Sky, sun/moon, fog and mood come from `blender-time-of-day`, so run `scene_mood.py` first, then add weather. Rendering settings are in `blender-rendering`.
4 
5## One call each
6```
7scripts/precipitation.py -- --type rain --intensity heavy --ground Street Roofs --wind 2 0
8scripts/surface_weather.py -- --objects Street Car Walls --wetness 0.7 --puddles 0.4 --ripples 1 --streaks 0.5
9scripts/lightning.py -- --flashes 2 --strokes 3
10scripts/precipitation.py -- --type snow --intensity moderate --ground Terrain
11scripts/surface_weather.py -- --objects Terrain Roofs --snow 0.8 --snow-depth 0.06
12scripts/surface_weather.py -- --objects Street Car Walls --remove     # exact restore
13```
14A rainy night: `scene_mood.py --time night --fog-visibility 250` → rain → wetness + puddles → lightning. Rain and puddles at night are what sell a wet scene: wet surfaces reflect every practical light.
15 
16## precipitation.py (rain, snow, dust, ash, embers)
17- Builds a GN modifier on `ENV_Weather_<Type>`. Its box covers what the camera sees across the frame range: world-fixed, so moving cameras don't drag the rain. With no camera, it covers a 18 m box. The floor is the lowest top of `--ground`.
18- **Seamless loop with no simulation**: each particle lives N whole times per loop (`Lives`), so the last frame + 1 equals the first frame exactly. It renders any frame on its own and works headless.
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