Clouds: shapes & layers¶
Metaplanets clouds are volumetric: they are ray-marched through 3D noise on the curved planet, so they have real thickness, cast shadows, glow at the edges when back-lit and look right from the ground, from an aircraft and from orbit.
A sky is built from layers. Each layer is one altitude band holding one cloud type. Stack several layers to build real weather, for example cumulus under cirrus, or a storm under a stratocumulus deck.
Two ways to add clouds¶
| Atmosphere Graph | Cloud Layer component | |
|---|---|---|
| How | A cloud node per layer in an Atmosphere Graph | + Add → Metaplanets Cloud Layer on the atmosphere actor (walkthrough) |
| Starting values | A preset per cloud type (altitude, coverage, density, shape) | Cumulus defaults whatever type you pick; set the altitude yourself |
| Best for | Designing a planet's whole sky, reusing it across levels | Hand-tuning one level, Blueprint control |
Both kinds can be on the same atmosphere at once. They render together, sorted by altitude.
Cloud types¶
The cloud type sets the vertical profile: how density is distributed from the base of the layer to the top, which gives the silhouette. The Atmosphere Graph nodes also fill in sensible starting values for each type:
| Type | Graph node | Band (km) | Coverage | Density | Shape | Look |
|---|---|---|---|---|---|---|
| Cumulus | Cumulus Clouds | 1.5–5 | 0.42 | 0.08 | 10 km cells, Fluffiness 0.5 | Rounded, puffy fair-weather clouds with flat bases. |
| Stratocumulus | Stratocumulus Clouds | 0.8–2.2 | 0.55 | 0.06 | 12 km cells, Fluffiness 0.35 | Low, flat, lumpy sheets with gaps. |
| Cumulonimbus | Cumulonimbus (Storm) Clouds | 1.2–12 | 0.25 | 0.12 | 16 km cells, strong storm cells | Towering storm clouds with anvils and a low shelf. |
| Nimbostratus | Nimbostratus (Rain) Clouds | 0.6–4 | 0.8 | 0.10 | Fluffiness 0.2, rain shafts on | A thick, grey, almost uniform rain deck. |
| Cirrus | Cirrus Clouds | 8–11 | 0.35 | 0.02 | 25 km cells, wispy at the top | High, thin, streaky ice clouds. |
Altitudes are above sea level
Every band is measured from the planet's sea level (its radius), not from the ground below. On mountainous worlds, raise low layers or they will sit inside the peaks.
How layers stack¶
- Every enabled layer on the atmosphere actor is rendered in the same pass, so layers that overlap in altitude blend correctly.
- Sort Priority (0–7) orders the layers; give lower layers lower numbers. Graph layers are numbered automatically in the order they are wired.
- An Atmosphere Graph holds up to 8 cloud layers. Each extra layer adds rendering cost, so most skies need only two or three.
- Clouds shadow the terrain and the layers below them.
A good real-world stack is one low layer (Cumulus, Stratocumulus or Nimbostratus) plus one high layer (Cirrus). Add Cumulonimbus only where you want storms.
Settings¶
The most useful settings are always visible. On graph nodes the rest are behind the arrow at the bottom of the node; on the component they are under the advanced section of Layer Params.
Shape and amount¶
| Setting | Default | What it does |
|---|---|---|
| Medium Type | Cloud | Cloud, Smoke, Ash or Steam / Fog. Changes how the medium scatters light. Use Ash or Smoke for volcanic plumes and polluted skies. |
| Altitude Inner / Outer Km | 1.5 / 5 | Bottom and top of the layer, above sea level. |
| Coverage | 0.42 | 0 = clear sky, 1 = full overcast. The most important setting. |
| Density | 0.08 | How thick each cloud is. Higher = darker, more opaque bases. |
| Fluffiness | 0.5 | High = soft, billowing puffs; low = sharp, eroded, wind-torn edges. |
| Shape Noise Scale Km | 10 | Size of the cloud cells. Earth cumulus is about 6–12 km; larger values give big cloud fields. |
| Detail Noise Scale Km | 1.6 | Size of the small-scale detail on cloud edges. |
| Detail Noise Strength | 0.38 | (adv.) How strongly the detail eats into the edges. |
| Extinction Scale | 8.5 | (adv.) Overall solidity: ~6 soft and translucent, ~10 balanced, ~16 very solid. |
| Density Contrast | 1.0 | (adv.) Pushes thin parts thinner and thick parts thicker. |
| Vertical Falloff | 0.35 | (adv.) How quickly density fades toward the top of the band. |
| Noise Stretch | (1, 1, 1) | (adv.) Stretches the noise per axis. Stretch X or Y for streaky, wind-sheared clouds. |
Weather and storms¶
| Setting | Default | What it does |
|---|---|---|
| Wind Velocity X / Y | 0.02 / 0.005 | Drift of the clouds, in km/s. |
| Upward Drift Km Per Sec | 0 | (adv.) Rising or sinking motion; positive values for convection and plumes. |
| Macro Weather Scale Km | 900 | (adv.) Size of planet-scale weather regions: where it's cloudy versus clear. Bigger = broader fronts. |
| Weather Mask Influence | 0.65 | (adv.) How much those weather regions decide coverage. 0 = clouds spread evenly. |
| Storm Cell Strength | 0.28 | (adv.) Clustering of clouds into convective storm regions. |
| Edge Detail Strength | 0.95 | (adv.) Extra raggedness at cloud edges. |
| SDF Scale Km | 180 | (adv.) Size of updraft cells (Earth: 100–300 km). |
| SDF Influence | 0.22 | (adv.) 0 = noise-only clouds, 1 = strong, organised storm towers. |
| SDF Shelf Strength | 0.85 | (adv.) The low shelf / gust front under storms. |
| SDF Anvil Strength | 0.75 | (adv.) The flat ice anvil at the top of storms. |
| Rain Shafts | off | Draws rain fog below the cloud base. |
| Rain Strength / Rain Depth Km | 1.0 / 1.0 | How dense the rain fog is and how far below the base it reaches. |
Noise by height¶
Four vectors, each a multiplier for the base / middle / top of the layer. They let one layer change character with height, like real clouds:
| Setting | Default | Effect |
|---|---|---|
| Puffy Noise By Height | (1.25, 1.0, 0.55) | Billowing body. High at the base gives cauliflower bottoms. |
| Wispy Noise By Height | (0.18, 0.45, 1.25) | Streaks. High at the top gives wispy, fibrous tops (cirrus uses 1.2 / 1.3 / 1.4). |
| Erosion Noise By Height | (0.45, 0.9, 1.35) | Edge erosion. |
| SDF Noise By Height | (0.35, 1.0, 0.65) | Where storm updrafts dominate. |
Lighting and colour¶
| Setting | Default | What it does |
|---|---|---|
| Medium Albedo | white | Cloud colour. Tint it for alien clouds or sulphur haze. |
| Absorption Tint | (0.08, 0.075, 0.065) | (adv.) Colour lost inside thick cloud. |
| Silver Lining Strength | 0.62 | Bright rim when the sun is behind a cloud. |
| Medium Anisotropy | 0.72 | (adv.) Forward scattering: how strongly clouds glow toward the sun. |
| Shadow Contrast | 1.25 | Darkness of the shaded side. |
| Powder Strength | 0.65 | The darkened "powder" look at the edges facing the sun, which gives volume. |
| Ambient Fill | 1.0 | Sky light in the shadows of clouds. Lower for moody, high-contrast storms. |
| Detail Lighting Strength | 0.65 | (adv.) Lighting detail on small features. |
| Deep Storm Tint | 0.75 | (adv.) Darkening deep inside storm cores. |
| Emissive Strength | 0 | Self-illumination, e.g. clouds lit from below by lava on a volcanic world. |
Quality¶
| Setting | Default | What it does |
|---|---|---|
| Noise Volume Resolution | 64 | (adv.) Resolution of the baked 3D noise (16–128). |
| Tile Noise | on | (adv.) Wraps the noise so it never ends at the edge of the wind. |
| Shape / Detail Noise Tile Km | 10000 / 2500 | (adv.) Wrap size. Keep it larger than the noise scale and scale it with planet size. |
Rendering quality for all layers is set on the AtmosphereComponent under Atmosphere → Cloud Quality and Cloud Shadows:
| Setting | Default | Notes |
|---|---|---|
| Cloud Render Downsample | 1 | 2 or 4 renders clouds at lower resolution, much faster, but needs temporal smoothing (experimental, below) to resolve the dither. Keep 1 for renders. |
| Use Cloud Temporal Smoothing (Experimental) | off | A temporal denoiser for the clouds. It still ghosts: clouds smear and trail when the camera or objects move. Leave it off for renders and shipping. |
| Cloud Near Step Km | 0.12 | Step size near the camera. Lower = crisper silhouettes, more cost. |
| Cloud Max March Iterations | 48 | Upper limit on samples per pixel. |
| Cloud Shadow Map Resolution | 384 | (adv.) Up to 512. |
| Cloud Shadow Extent Km | 80 | Area around the camera that receives cloud shadows. |
| Cloud Shadow Strength | 0.75 | How dark cloud shadows are on the ground. |
Recipes¶
Each recipe lists the layers and the values that differ from the type's defaults. Build them as graph nodes into a Cloud Stack, or as Cloud Layer components.
Fair-weather day¶
Scattered cumulus with thin cirrus above. This is AG_Earth and AG_Canopy.
- Cumulus: Coverage 0.3–0.38.
- Cirrus: Coverage 0.2–0.25.
Overcast and rain¶
- Nimbostratus: Coverage 0.8–0.9, Rain Shafts on, Rain Strength 1.5.
- Lower Ambient Fill to ~0.7 for a flat, grey light.
- Add a Ground Fog node with Density ~0.08 in the graph for wet, low visibility.
Thunderstorms¶
The AG_Storm example:
- Cumulonimbus: Coverage 0.42.
- Stratocumulus: Coverage 0.55 underneath.
- Haze Density 2.4 and Ground Fog Density 0.09 in the same graph.
For larger, more organised storm towers, raise SDF Influence to 0.8–1.0 and Storm Cell Strength to 0.8–1.2 on the cumulonimbus layer.
Low marine deck¶
A sheet of stratocumulus over the sea, broken into cells:
- Stratocumulus: band 0.4–1.2 km, Coverage 0.65, Shape Noise Scale Km 20, Fluffiness 0.3.
High ice clouds on a thin atmosphere¶
The AG_Mars example: a single, faint, high layer.
- Cirrus: band 15–24 km, Coverage 0.2, Density 0.008, Medium Albedo (0.85, 0.92, 1.0).
Haze deck on a thick world¶
The AG_HazyMoon example: a warm layer lifted high into a deep atmosphere.
- Stratocumulus: band 8–14 km, Coverage 0.5, Medium Albedo (1.0, 0.85, 0.6).
- Output AtmosphereHeight 400.
Alien clouds¶
The AG_Alien example: ordinary shapes, unusual colours.
- Cumulus: Coverage 0.32, Medium Albedo (0.9, 1.0, 0.96).
- Cirrus: Coverage 0.4, Medium Albedo (1.0, 0.78, 0.95).
Volcanic plume or ash sky¶
- Cumulus layer with Medium Type = Ash, Medium Albedo (0.35, 0.33, 0.32), Density 0.15, Upward Drift 0.05.
- Emissive Strength 2–6 with an orange Medium Albedo on a low layer gives clouds lit from below by lava.
Wind-sheared streaks¶
- Cirrus with Noise Stretch (4, 1, 1) and Wind Velocity X 0.08.
Limitations¶
- Seen from the ground, a layer goes from clear to a fairly uniform veil as coverage rises; individual cumulus cells are not yet strongly separated at high coverage. Keep cumulus coverage under ~0.45 for distinct clouds.
- Procedural storm cells (Cumulonimbus with storm strength) are placed on the world XY plane rather than wrapping the whole sphere.
- Low cloud layers seen from high altitude (above roughly 30 km, and from orbit) show concentric "onion-ring" banding. For orbital shots, keep only high, thin layers such as Cirrus enabled, and bring low decks in below about 20 km.
- Since 2.1.0, cloud noise is sampled on the sphere (no seams or polar streaks). Levels made before 2.1.0 get statistically similar but different cloud patterns.
Performance
Clouds are usually the most expensive part of the sky. Use two or three layers, not eight, and raise Cloud Near Step Km a little for games. For cinematics, keep downsample at 1 and lower Cloud Near Step Km for crisp silhouettes. Don't rely on temporal smoothing for either: it is experimental and ghosts.