Fog Area

Fog Area is a handy, blueprint-based tool that adds procedural, noise-driven local fog to your scenes. It is easy to use and highly customizable. The package includes pre-baked noise textures for optimized runtime performance. The core fog shader supports two types of local volumes: sphere and box.

Quickstart

To see local fog in action right away, drag a Fog Area blueprint actor from the Content Browser or the Place Actors tab into your scene.

If the fog is invisible, ensure that Volumetric Fog is enabled in your Exponential Height Fog actor.

Material Modes

Splitting materials into dynamic and static types helps boost performance. Static materials avoid creating a dynamic material instance for every fog actor in the scene, reducing overhead.
Almost all properties available in the fog shader are exposed in the Fog Area actor. You can configure a dynamic fog area with your preferred settings and then transfer those settings to a static version without needing to open the Material Editor.

General Data

Wind

The wind direction can be set to either Local or World space using the Wind World Space variable.

• Local Wind: Driven by the actor’s forward (X) axis.
• World Wind: World Wind uses a global direction. While it is technically possible to pass per-instance data to static materials using Custom Primitive Data, I chose to keep the shader simpler and avoid that complexity. Instead, for world-space wind, connect your global wind vector (e.g., from a Material Parameter Collection) to the Global Wind input pin in the Fog shader and recompile.

Noise

Shape Data

Allows you to mask the fog with a 2D texture, creating any shapes.

Advanced

Modes

Fog Area includes three specialized operational modes: Shadows, Distance Field, and Light Shafts.

Under the hood this modes are just regular material instances with pre-configured shader switches. Materials are stored as Soft pointers to minimize memory usage and reduce dependencies from a Fog area actor.

Shader Complexity

Base noise only

Every feature is enabled

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The primary reason for splitting the material into distinct instances is performance. By pre-configuring the shader switches, the number of shader instructions is greatly reduced, allowing you to use many instances without worrying about performance impact.

Bellow is an example map in Shader Complexity debug view with different modes active on various Fog Area actors.

Self Shadows Data

Distance Field Data

If the Distance Field mode doesn’t produce any effect, make sure that Generate Mesh Distance Fields is enabled in Project Settings.

Shafts Data (Light Shafts)