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

Component-Based Approach

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 preset.

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 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.

To speed up the creation of a new preset, you can copy struct parameters more quickly. Right-click the struct parameter (or use the shortcut 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:

1. Set wind direction before the Fast Clouds main function in the Construction Script.
2. 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.

Volumetric clouds material

Cloud shadows light function

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Main Parameters

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.

Base Noise

Base noise and detail noise share the same structure and act similarly, but each adds another layer of granularity.

Detail Noise

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.

Cloud Shadows

Cloud shadows are built from the directional light (if referenced) and are a cheap approximation of volumetric clouds.

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.

Fast clouds, cloudy preset and shadows

Default in Unreal

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Cloud Profiles

Cloud profiles allow you to control the shape of each cloud layer.

To create a custom cloud profile, follow the steps below: