Wind
Renzora has one wind. Set a speed and a bearing on the World Environment and every system that should respond to weather does: grass lays over, tree canopies sway and rustle, cloth and flags pull downwind, the cloud deck drifts on the same heading, and the ocean builds to a rougher sea state.
That sounds obvious, and it is the point. Before this existed each of those systems had its own private wind knob, so a scene could easily end up with grass leaning east under clouds sailing west — the kind of mismatch nobody consciously notices and everybody reads as "this looks fake".
Quick start
- Select the World Environment entity in the outliner.
- Open the Wind section in the inspector (Rendering category).
- Drag Speed up from the default 4 m/s and watch the whole scene respond.
There is nothing to add or enable per-scene — every scene has a wind, calm by default is still a light breeze, and the toggle in the section header turns it off entirely.
The controls
| Field | What it does |
|---|---|
| Direction | Compass bearing the wind blows toward, in degrees. 0° is +X, 90° is +Z. |
| Speed | Sustained speed in m/s. 4 is a gentle breeze, 12 is a fresh-to-strong breeze (the reference point everything is tuned against), 25+ is a storm. |
| Gust Strength | How far gusts lift the speed above sustained, 0–1. At 0.5 a gust peaks at 1.5× Speed. 0 is a perfectly steady wind, which reads as artificial. |
| Gusts / sec | Gust rate. 0.15 (one gust every ~7 s) is natural outdoor wind; above 1 it stops being gusting and becomes buffeting. |
| Turbulence | Cross-wind chaos, 0–1. This is what stops foliage from all swinging along one axis like a row of metronomes. |
Direction is "toward", not "from". Weather forecasts report the direction wind comes from, which is the opposite of what a shader wants. Renzora stores travel direction, so a bearing of 90° pushes things toward +Z.
What responds to it
Grass and terrain foliage
Automatic. Each foliage layer keeps its own Wind Strength in the terrain foliage settings, which is now a response multiplier rather than a wind: stiff sedge at 0.4, tall meadow grass at 1.0. Turning the world wind down calms every layer regardless of what they are set to.
How far a blade leans also scales with how long the blade is, normalised against a 0.25 m reference so the default height range keeps the motion it already had. Grass grown with the Grow brush therefore sweeps further than the cropped grass beside it, rather than leaning the same absolute distance and reading as stiffer.
Gusts travel spatially, so a gust front visibly sweeps across a field rather than every blade surging at once. That front is also broken up by a noise field drifting downwind, so a surge arrives as patchy cells rather than a straight band running to the horizon — the envelope decides when a gust happens, the noise decides where it lands.
Individual blades are decorrelated on top of that. Every blade gets its own sway speed, amplitude and heading, hashed from where it stands, so neighbouring blades beat against each other and the field never resynchronises. This is why grass doesn't read as a repeating pulse: a field of oscillators that all run at one frequency returns to its starting arrangement every cycle no matter how their phases are offset, and what you see is the whole field breathing in and out on a fixed period. Turbulence widens the per-blade heading spread, so a steady wind still combs the field one way while a gusty one scatters it.
Trees and plants
Procedural trees sway out of the box — the generator writes per-vertex stiffness weights into the mesh, and the wrapper tags both the trunk and the leaf canopy with a Wind Sway component tuned for each.
For anything else — an imported bush, a hand-modelled palm, a fern — add Wind Sway from the inspector:
| Field | What it does |
|---|---|
| Response | Multiplies the world wind for this mesh. Stiff shrub ≈ 0.4, willow ≈ 1.6. |
| Flutter | High-frequency leaf rustle, independent of the branch sway. Set to 0 for anything woody that should only bend. |
| Amplitude | How far the floppiest vertex travels at reference wind, in metres. |
| Pivot Height | Fallback only. Height at which a mesh with no authored wind weights counts as fully flexible. |
Adding Wind Sway swaps the mesh's material for a wind-animated variant of the same material — you keep alpha cutouts, lighting, shadows and everything else. Removing the component puts the original back. Meshes that share a material and the same Wind Sway settings share one animated material too, so a forest of a hundred identical trees costs one.
Authored weights vs. the fallback. Motion quality depends on where the
per-vertex stiffness comes from. A procedural tree carries real weights in its
UV_1 attribute — 0 at the trunk base, 1 at a twig tip — so it bends the way a
tree bends. A mesh without them falls back to a height ramp: rigid at the object
origin, flexible at Pivot Height. That looks right on a bush and wrong on
anything with a long horizontal branch, which will swing as a rigid arm.
Cloth
Automatic. Cloth follows the instantaneous wind including gusts, so a flag snaps in the same gust that flattens the grass beneath it. The world wind occupies the first slot in the cloth wind list; any extra forces a scene pushes (a scripted downdraft, a fan) add on top rather than being overwritten.
Clouds
The cloud deck takes its heading from the world wind and scales its drift with wind strength, controlled by Follow World Wind on the Clouds component (on by default). The authored Speed stays meaningful — it is the drift the deck reaches at reference wind.
Two deliberate differences from ground-level foliage:
- The deck ignores gusts entirely. Cloud features are kilometres across; a two-second gust does not move them.
- It never fully stops. Air aloft is always moving, so even a dead-calm scene keeps a slow drift. A frozen sky looks more wrong than a drifting one.
Turn Follow World Wind off for a deliberately decoupled sky — a stylised level, or a cutscene where the ground wind is scripted and the sky must not change.
Oceans
The FFT ocean scales its whole sea state with the world wind, via Follow World Wind on the Water Surface component (on by default) and Wind Response (how much of the wind reaches this surface — a sheltered bay is ~0.4, open ocean 1.0).
The authored per-cascade wind speeds and bearings become the sea's shape — the swell-to-wind-sea balance, the relative headings — and the world wind scales and rotates that set as a whole. Turn the wind up and the same ocean gets harsher without becoming a different ocean. Turning the flag off restores exactly the sea you authored.
The ocean lags, on purpose. It follows a heavily smoothed wind, so the sea takes tens of seconds to build after you turn the dial. This is not a shortcut. Wind speed is an input to the JONSWAP wave spectrum, so every change re-bakes the cascade textures — and a real sea takes hours to build to a new wind, so a sea that snapped instantly would look wrong as well as cost more. Watch the swell arrive after the gust; that delay is the effect working.
Scripting
-- Speed in m/s, direction in degrees the wind travels toward.
set_wind(14.0, 90.0)
-- Gust depth (0-1), gusts per second, cross-wind turbulence (0-1).
set_wind_gusts(0.7, 0.3, 0.6)
-- Reading goes through reflection.
local speed = get("WindState.speed")
A storm rolling in is a script that ramps set_wind over time — the ocean's
natural lag will make the sea build behind it without any extra work.
Notes and limits
- Shading normals do not bend with the geometry. A swaying branch keeps the normals it was built with. At sane amplitudes the error is invisible; at very high Amplitude on large woody geometry it can show as lighting that does not quite track the motion.
- Wind is uniform across the level. There are no local wind zones yet — no explosion gusts, no rotor wash, no shelter behind a cliff. Gusts do travel spatially, so wind is not static, but every point of the world sees the same wind field.
- Wind Sway needs a StandardMaterial. A mesh already using a procedural graph material is not swapped; author the sway into the graph with the Wind node in the material editor instead.