Sky, weather and climate

The environment is project-wide. It covers the sky and the sun, the clock, clouds, the weather, the season, the climate that ties temperature to snow, ice and fire, and small ambient touches such as fireflies and birds. All of it previews live in the editor and runs the same way in an exported game.

Most settings live in Window → World & terrain, on the Environment, Weather and Ambience tabs.

Apply a lighting look

A lighting look sets the time of day, haze and volumetric sun shafts, bloom, ambient occlusion and colour grading in one undo step. Water and a painted sky are kept.

1. Open Window → World & terrain → Environment.
2. Click a look next to Lighting look.
3. Fine-tune the individual settings below it.

Look	Description
Clear day	Bright noon, crisp shadows and a light haze
Battlefield	Dusty warm daylight with sun shafts through the haze
Golden hour	Low orange sun, long shadows and glowing shafts
Overcast	Soft grey light and muted colours
Foggy dawn	Cold blue morning mist with soft shafts
Night battle	Moonlit night in smoky haze; explosions and lamps light the fog
Storybook	Warm, saturated and soft

Looks with volumetric haze switch anti-aliasing to TAA so the shafts render smoothly.

Choose a sky

Set Sky on the Environment tab:

Sky	Description
Classic	A stylised flat sky with linear fog. This is the default
Physical	A scattering atmosphere with HDR exposure and tonemapping

Physical atmosphere

With Sky set to Physical, the Atmosphere (Physical sky) section shapes the sky through the day.

Setting	Field	Range	Default
Air (blue sky, red sunsets)	air	0–5	1
Air tint	air_tint	sRGB multiplier	White
Haze	haze	0–20	1
Glow around the sun	haze_glow	0–0.99	0.8
Ozone	ozone	0–5	1
Atmosphere height	height_km	10–400 km	100
Sun size	sun_size	0–10°	0.53
Sun brightness	sun_brightness	0–20	1
Distance haze	distance_haze	0–50	8
Stars at night	stars	0–1	0.6

Distance haze fades far land into the air. Raise it to make a small world feel larger.

Sky library and skyboxes

A skybox is a painted 360° panorama drawn behind everything. It also lights the scene in its own colours and replaces the generated sky.

1. In the Sky section, click a sky in the library gallery to use it.
2. Adjust the fit:

Setting	Field	Range	Default
Turn sky °	rotation	−180 to 180	0
Horizon tilt °	horizon	−10 to 10 in the panel, −20 to 20 by command	0
Brightness	brightness	0–3 in the panel, 0–4 by command	1
Lights the scene	lighting	0–3	1
Match fog, water and light colours	match_colors	On/off	On

3. Click Use the generated sky to remove the skybox.

The library holds folders that each contain a 2:1 equirectangular PNG. Run python3 scripts/fetch_skies.py in the engine repository to download free stylized skies into it, then click Refresh library. Import your own panorama, folder or skybox .zip with sky.import. When you set a skybox this way, a painted sun is turned to match the scene’s sun unless you pass "align_sun": false.

Painted sky and night

The Classic sky can use a Painted sky (gradient dome) with zenith and horizon colours, a Moon disc, stars, wispy clouds and a sky drift speed. The moonlight follows the moon’s direction and elevation. Tension colours the sky tints the dome by the game’s tension; scripts call set_sky_mood(mood) with 0 (calm), 1 (tense) or 2 (peak).

The night settings control the moonlight colour and strength, the night sky colour, and the night fill light.

Set the time of day

Setting	Field	Range	Default	Description
Time of day	time_of_day	0–24 h	13:00	Play starts at this time
Day length (min)	day_length_minutes	0–120 in the panel, 0–1,440 by command	0	Real minutes per in-game day during Play. 0 freezes the clock
Sunrise direction °	sun_azimuth	−180 to 180 in the panel, −360 to 360 by command	120	Compass direction of sunrise
Sky light	sky_light	0–4	1	How brightly the sky fills shadowed areas by day

Scripts read and change the clock with hour(), minute(), time_of_day(), set_time(hour) and set_day_length(minutes).

The same tab holds fog distance, bloom, ambient occlusion and exposure; see Post-processing. Sun shadows are covered in Lighting, and the water look in Water and fluids.

Volumetric clouds

Volumetric clouds are 3D clouds lit by the sun. They drift with the wind, shade the ground and show in the water. Turn on Volumetric clouds in the Clouds section.

Setting	Field	Range	Default
Volumetric clouds	enabled	On/off	Off
Coverage	coverage	0 (clear) – 1 (overcast)	0.5
Density	density	0–3	1.2
Altitude	altitude	50–4,000 m in the panel	500 m
Thickness	thickness	50–3,000 m in the panel	800 m
Size	scale	0.2–5	1
Drift speed	speed	0–5	1
Shadows	shadows	0–1	0.6
Wispy edges	detail	0–1	0.5
Tint	color	sRGB multiplier	White
Painterly light	stylized	On/off	On

Note

Volumetric clouds are off on the Low graphics setting, and they switch the camera from MSAA to SMAA.

Weather

When the weather is on, it drives the clouds, sun and sky light, fog, the physics wind that pushes loose objects and boats, waves, rain and snow, wet ground and puddles, lightning and tornadoes. Rain and snow stop under roofs.

1. Open Window → World & terrain → Weather.
2. Turn on Weather on and pick the starting weather.
3. Turn on Changes by itself to follow the forecast, or leave it off to keep one weather.
4. Under Forecast, set a weight for each weather. Higher weights come up more often.
5. Under Weathers, tune a built-in weather or click New to add your own.

Built-in weathers: Clear, Cloudy, Overcast, Rain, Storm, Thunderstorm, Snow, Blizzard, Fog, Sandstorm and Tornado. The default forecast cycles between Clear, Cloudy, Overcast, Rain, Storm and Thunderstorm.

Setting	Field	Range	Default
Weather on	enabled	On/off	Off
Changes by itself	automatic	On/off	On
Lasts at least / at most	duration_minutes	0.1–60 min in the panel, 0.1–240 by command	3–8 min
Change takes	transition_seconds	0–300 s in the panel, 0–600 by command	40 s
Soaked after	wetting_minutes	0.05–10 min in the panel	0.6 min
Dry after	drying_minutes	0.05–30 min in the panel	2.5 min
Puddles	puddles	On/off	On
Lightning breaks things	lightning_damage	On/off	Off
Volume	volume	0–2	1

Weather settings

Setting	Field	Range
Cloud cover	clouds	0–1
Storm clouds	cloud_darkness	0–1
Wind	wind	0–60 m/s
Gusts	gust	0–1
Rain	rain	0–1
Snow	snow	0–1
Fog	fog	0–1, with a fog colour
Sunlight	light	0–1
Waves	waves	0–3
Wet ground	wetness	0–1; puddles form above about 0.6
Lightning	lightning	0–30 strikes per minute
Tornado	tornado	On/off

You cannot delete the starting weather. The Sounds section replaces the built-in rain, heavy rain, wind, storm, tornado and near and far thunder sounds with project sounds.

During Play, scripts change the weather with set_weather(name, seconds) and read it with weather(), wetness() and snow_cover(). lightning_strike(x, z), spawn_tornado(x, z) and stop_tornado() trigger events directly.

Example: a stormy evening

You’ll set a late-evening light, cover the sky in volumetric cloud and hold a thunderstorm over the level. Start from a new project (File → New project…); weather is off in new projects.

1. Open Window → World & terrain and select the Environment tab.
2. Next to Lighting look, click Golden hour. It sets the clock to about 18:18 and turns on volumetric haze.
3. Drag the Time of day slider until its label reads Time of day 19:30.
4. In the Clouds section, turn on Volumetric clouds and set Coverage to 0.9.
5. Select the Weather tab. Turn on Weather on, set Starting weather to Thunderstorm and turn off Changes by itself so the storm never clears.
6. Press Play. Rain falls, the ground darkens with wetness, the wind picks up and lightning strikes at random.

Do the same from the command line:

feather-cli --workspace ./stormy-evening command project.create \
  --json '{"name":"Stormy Evening"}' --save project.feather.json

feather-cli --workspace ./stormy-evening --project project.feather.json command environment.look \
  --json '{"look":"golden_hour"}' --save project.feather.json

feather-cli --workspace ./stormy-evening --project project.feather.json command project.environment \
  --json '{"time_of_day":19.5,"clouds":{"enabled":true,"coverage":0.9}}' --save project.feather.json

feather-cli --workspace ./stormy-evening --project project.feather.json command weather.set \
  --json '{"patch":{"enabled":true,"current":"thunderstorm","automatic":false}}' \
  --save project.feather.json

Check it worked by simulating four seconds with an extra lightning strike near the player start:

feather-cli --workspace ./stormy-evening --project project.feather.json command game.simulate \
  --json '{"frames":240,"weather":[{"frame":60,"action":"strike","at":[5,-5]}]}'

The report’s weather section shows "current": "thunderstorm", "rain": 1.0, "wind": 12.0 and a strikes count of at least 1. weather.get confirms "enabled": true and "automatic": false.

Seasons

The season changes generated trees, falling leaves and grass. Broadleaf trees get fresh leaves and blossom in spring, look as designed in summer, turn orange, red and gold in autumn, and go bare in winter. Pines and palms stay green and are dusted with snow in winter.

1. Open Window → World & terrain → Trees.
2. Next to Season, pick Spring, Summer, Autumn or Winter. The default is Summer.
3. To cycle during Play, turn on Changes by itself and set the in-game days per season (0.05–365, default 3).

Scripts use set_season(name) and season().

Climate

The climate gives every place and moment a temperature and a moisture, so the systems that care about cold, heat and damp agree with each other. Temperature starts from a base, shifts with the biome, cools with altitude, swings with the season and time of day, and drops in rain. Moisture comes from the biome and the rain.

From that:

• Rain falls as snow below Snow below, and snow settles.
• Simulated water freezes to ice below Water freezes below and thaws again above it.
• Fire runs faster through hot, dry ground and stalls in cold, damp ground.
• Fireflies need at least about 6 °C and are at full strength from 14 °C. Butterflies need about 9 °C and are at full strength from 17 °C.

Open Window → World & terrain → Weather and expand Climate.

Setting	Field	Range	Default
Climate on	enabled	On/off	On
Base temperature	base	−30 to 40 °C	16 °C
Biome spread	biome_span	0–40 °C	18 °C
Colder with height	lapse	0–5 °C per 100 m	0.65
Season swing	season_swing	0–30 °C	9 °C
Night chill	day_night	0–25 °C	7 °C
Rain cools by	rain_cooling	0–15 °C	4 °C
Snow below	snow_below	−10 to 10 °C	0.5 °C
Water freezes below	freeze_below	−40 to 5 °C	−3 °C
Cold rain becomes snow	cold_snow	On/off	On
Water freezes	freezing	On/off	On
Heat and drought feed fire	fire_dryness	On/off	On

The base temperature applies to a middling biome at sea level, in spring, at mid-afternoon in clear weather. The day is warmest at 15:00 and coldest at 03:00. Water freezes below cannot be more than 5 °C above Snow below.

Scripts and Blueprints read the climate with temperature() (at the camera), temperature_at(x, z) and moisture().

Snow and sand

Lying snow and loose sand form a field around the camera during Play that feet, bodies and blasts push about. The player, enemies, NPCs and moving bodies press trenches with berms beside them, blasts throw the snow or sand clear, and steep walls slump back. Falling snow fills tracks back in, and the wind smooths sand. Deep fresh snow or sand slows the player; a trodden track much less.

Snow lies only while the weather has a snow cover, as deep as Snow depth under a full cover. It settles on open, gentle ground, not under roofs, on cliffs or in rivers. Sand lies on one texture layer, or on all ground with Sand everywhere.

Open Window → World & terrain → Weather and expand Snow & sand.

Setting	Field	Range	Default
Snow and sand on	enabled	On/off	On
Detail	cell_size	0.1–0.5 m per cell; smaller shows finer footprints	0.25 m
Cells across	cells	64–256	160
Snow depth	snow_depth	0–1.5 m	0.35 m
Snowfall refills tracks in	snow_refill	5–3,600 s	240 s
Snow colour	snow_color	sRGB	Near white
Sand	sand	On/off	Off
Sand everywhere	sand_everywhere	On/off	Off
Sand texture layer	sand_layer	0 (base layer) – 3	0
Sand depth	sand_depth	0–0.6 m	0.12 m
Wind ripples	ripples	0–1	0.5
Wind smooths sand in	sand_refill	5–3,600 s	600 s
Sand colour	sand_color	sRGB	Pale tan
Slows walkers	slow	0–0.9	0.45

Cells across × Detail is how far the field reaches; the default covers 40 m.

Function	Description
drift_depth_at(x, z)	Metres of lying snow or sand there; 0 outside the field
drift_carve(x, z, radius)	Throws snow or sand out of a disc into a heap around it
drift_pile(x, z, radius, height)	Heaps snow or sand up, height metres in the middle; a negative height scoops it out

Ambience

Ambience adds small living details that react to the wind, weather and time of day. It is on by default. Open Window → World & terrain → Ambience. Amounts run from 0 (off) through 1 (normal) to 2 (double).

Setting	Description
Wind trails	Bright streaks that fly with the wind over the land, sometimes curling a loop. Need wind
Leaves	Leaves blown on the wind, more in gusts. Kind: Leaves, Autumn, Petals or Blossoms
Dust motes	Drift in daylight
Fireflies	Blink at dusk and at night
Butterflies	Come out on calm, dry days
Bird flocks	0–8 flocks circling overhead
Birds land nearby	One flock lands near the player and takes off when the player comes within Birds take off at (1–40 m)

Rain, snow, night and strong wind thin or hide each kind. Winter removes butterflies and thins fireflies. Underground, leaves, wind trails and butterflies disappear.

The built-in grass is configured on the same tab; see Foliage and biomes.

Scripts use set_ambience(feature, amount) until Play stops, and scatter_birds().

Limits

• Time of day is 0 to just under 24 hours; day length is at most 1,440 real minutes.
• A forecast holds up to 64 entries. Weather names are 1–64 characters.
• Volumetric clouds are unavailable on the Low graphics setting.

Automate it

This applies the golden hour look, switches to the physical sky with a 20-minute day, and starts a rainy forecast:

feather-cli --connect .feather-session.json command environment.look \
  --json '{"look":"golden_hour"}'

feather-cli --connect .feather-session.json command project.environment \
  --json '{"sky":"Physical","day_length_minutes":20,"clouds":{"enabled":true,"coverage":0.6}}'

feather-cli --connect .feather-session.json command weather.set \
  --json '{"patch":{"enabled":true,"current":"rain","automatic":true,"forecast":[{"weather":"rain","weight":3},{"weather":"storm","weight":1}]}}'

For a desert, turn on sand everywhere:

feather-cli --connect .feather-session.json command drifts.set \
  --json '{"patch":{"sand":true,"sand_everywhere":true,"sand_depth":0.2}}'

Command	Purpose
environment.look	Applies a lighting look
project.environment	Patches the sky, clock, atmosphere, clouds, painted sky, night and skybox
sky.library / sky.use / sky.import	Lists library skies, uses one, or imports a panorama
weather.get / weather.set	Reads and patches the weather settings
weather.upsert / weather.remove	Creates, edits or deletes a weather
season.get / season.set	Reads and patches the season
climate.get / climate.set	Reads and patches the climate
drifts.get / drifts.set	Reads and patches the snow and sand settings
ambience.get / ambience.set	Reads and patches the ambience

See Agents & automation for connecting a live session.