Fast Clouds
Fast Clouds is a component based data-driven, multi-layered, cloud profiles driven volumetric clouds shader. It comes with multiple presets and the ability to create your own. Includes proxy cloud shadows based on a directional light function. Each cloud profile is customizble and drived by curves. The package includes pre-baked volume noise textures for optimized runtime performance.
Presets included:
- Cloudy
- Partly
- Wispy
- Fluffy
- Overcast Dark
- Overcast Light
- Storm
- Stylized
- Stylized 2
Quickstart
There are two ways to get started: place the Fast Clouds actor directly in a level, or use it with your own custom sky actor.
Actor-Based Approach
Place Fast Clouds
To see Fast Clouds in action right away, drag the Fast Clouds Blueprint actor from the Content Browser or the Place Actors tab into your scene.
Connect Volumetric Clouds
Scroll down in the Fast Clouds actor, find the Volumetric Clouds variable, and select the Volumetric Clouds Actor from your scene.
(Optional) Connect Sky Atmosphere & Directional Light
Optionally, you can connect a Sky Atmosphere to Fast Clouds, which will change some parameters based on the cloud preset. A reference to the Directional Light is necessary for proxy cloud shadows to work.
(Optional) Change Preset
You can select from number of pre-built presets.
Component-Based Approach
Add Component
Navigate to your custom Sky actor, press the Add button at top-left windon, and find AC_FastClouds actor component.
Initialize Component
In the Construction Script or Begin Play, add the nodes in the order shown below. Component references should be first for correct behavior.
General
The Fast Clouds actor is a wrapper around the AC_FastClouds actor component. The actor can be placed directly in a level or serve as a container for creating a custom cloud presets.
AC_FastClouds is an actor component designed for easy integration into a custom sky actor. The component uses a Preset‑only approach — it relies on data assets and does not support custom clouds creation.
The actor wrapper, however, features two separate modes: Custom and Preset. Both modes serve the same purpose but are split to offer flexibility in workflow.
- Custom Mode — Available only in the actor. Allows you to create a cloud preset from scratch directly within the actor.
- Preset Mode — Available in both the actor and the component. Uses a data asset containing the same parameters, enabling you to quickly switch between different visual presets.
Shift+RMB) to copy the entire struct. Then use Shift+LMB to paste the data into a cloud preset.
Wind Direction
Wind Direction is a local Fast Clouds parameter. If you want to use your own global wind, there are two strategies:
- Set wind direction before the Fast Clouds main function in the Construction Script.
- Use a Material Parameter Collection.
Connect your global wind to the Wind Direction input pin in the Volumetric Clouds material and the Cloud Shadows light function material, then recompile both.
Wind Offset parameter drives the animation, and the wind direction in the material is ignored.Main Parameters
| Variable | Default Value | Description |
|---|---|---|
| Profile Row | 0 | The index or row of the cloud profile. |
| Density | 1.0 | General cloud density. |
| Wind Speed | 0.5 | Wind speed value. |
| MultiScatter | 0.8, 0.5, 0.3 | Multi-scattering values. |
| Phase | 0.5, -0.5, 0.25 | Phase function values. |
| Albedo Color | White | Clouds albedo color. |
| Emissive Color | Black | Emissive color setting. |
Map
The Map serves as the foundational 2D layer that defines the overall cloud silhouette. It is also critical for optimization: Unreal Engine leverages conservative density estimation and empty-space skipping, and this 2D layer significantly accelerates ray marching.
The most impactful parameters are Sharpness and Intensity, which enable the construction of multi-layered clouds. Note that each layer—even with low intensity—adds some performance cost. I recommend using at most 1–2 layers and experimenting with the Sharpness value.
Each vector channel corresponds to a cloud layer, which is mapped to a curve float value to shape the cloud at a specific height.
| Variable | Default Value | Description |
|---|---|---|
| Scale | 120.0 | Map base scale (in kilometers). |
| Speed | 0.5 | Map base speed. |
| Density | 1.0 | Map base density. |
| Texture | None | Overridable base map texture. |
Base Noise
Base noise and detail noise share the same structure and act similarly, but each adds another layer of granularity.
| Variable | Default Value | Description |
|---|---|---|
| Scale | 14.0 | Base noise scale. |
| Speed | 40.0 | Base noise speed. |
| Sharpness | 0.25 | Base noise sharpness. |
| Intensity | 1.0 | Base noise intensity. |
Detail Noise
| Variable | Default Value | Description |
|---|---|---|
| Scale | 14.0 | Detail noise scale. |
| Speed | 40.0 | Detail noise speed. |
| Sharpness | 0.25 | Detail noise sharpness. |
| Intensity | 1.0 | Detail noise intensity. |
| Altitude Offset | 0.0 | Offsets noise by normalized height in layer. |
| Altitude Intensity | 1.0 | Scales the altitude detail mask. |
Distortion
Distortion affects the base noise and allows for stylized clouds. It is not enabled in the default cloud material and can be quite expensive.
| Variable | Default Value | Description |
|---|---|---|
| Scale | — | Distortion scale (in kilometers). |
| Intensity | — | Distortion intensity. |
Cloud Shadows
Cloud shadows are built from the directional light (if referenced) and are a cheap approximation of volumetric clouds.
| Variable | Default Value | Description |
|---|---|---|
| Enable Shadows | false | Enables the proxy cloud shadows |
| Cloud Shadows Intensity | 1.0 | Simple multiplier for shadow intensity. |
| Cloud Shadows Exponent | 2.0 | Scales shadow strength using an exponent. |
Performance Comparison
Below is a comparison between the default Fast Clouds preset (with extra cloud shadows) and Unreal’s native clouds material. The performance of Unreal’s clouds material heavily depends on coverage, but generally Fast Clouds is more performant compared to the native material.
Cloud Profiles
Cloud profiles allow you to control the shape of each cloud layer.
To create a custom cloud profile, follow the steps below:
Navigate to Curve Creation
In the Content Browser, navigate to Miscellaneous → Curve, as shown below.
Select Curve Class
Select a Linear Curve in the new editor window.
Modify Curve
The curve should be in the 0–1 range on both axes. Only XYZ or RGB curves are valid; Alpha is not used.
Navigate to Curve Atlas
In the Content Browser, navigate to the Data folder and find CC_CloudProfiles.
Add Curve to Atlas
In the curve atlas windows, find Texture Height parameter and increase value by 1, it will create additional slot for atlas.
Press plus button in Gradient Curves and assign your custom cloud profile.
Presets Blend
Fast Clouds supports blending presets at runtime.
Dynamic blending adds an extra texture sample of Cloud Profiles and is slightly heavier than the original clouds without blending. It is enabled by default in the M_VolumetricClouds material. If your project only needs the static version, you can disable it by creating a material instance and turning off dynamic blend, as shown below.
To blend presets at runtime:
- Call
EnableBlendingat Begin Play or before the first blend. - Call
Set New Preset Databefore each blend to define the target preset. - Call
Blend New Preset— the main function that blends two presets together. It takes a float parameter in the0 to 1range. - Optionally call
Finish Blendafter the new preset is fully blended, so a future preset can be blended.
Blending supports several scenarios, such as blending to a new preset each time or flip‑flopping (forward and reverse) between two presets. However, due to the architecture of Cloud Profiles, a new preset cannot be blended while a blend is already in progress.