In this lesson, you will learn how to unify your large-scale environment by integrating Volumetric Clouds and Exponential Height Fog to create a cohesive, depth-aware atmosphere.
When working with World Partition, your lighting and atmospheric systems must support the vast scale of your streaming cells without visual popping or discontinuity at the horizon. The goal is to blend your skybox, cloud layers, and fog so that distant objects naturally recede into the atmosphere, maintaining a sense of scale across your massive maps.
Establishing Atmosphere Depth
The Volumetric Cloud actor acts as the primary volume for your weather systems. To ensure consistency, you must link its properties with the Exponential Height Fog. A common mistake is treating these as isolated systems; instead, use the "Volumetric Fog" feature within your fog actor to ensure that the light shafts and density from your clouds interact with the atmosphere at ground level.
To ground your volumetric clouds in the world, use a Sky Atmosphere component. This provides the physical math for Rayleigh and Mie scattering, which defines how light bends as it passes through the atmosphere.
Implementation Tip: Linking Fog to Atmosphere
You can influence the fog's density based on the distance from the player to prevent harsh silhouettes in your distant HLODs. Ensure your Fog Density is low but paired with a high Volumetric Fog Distance to push the "haze" out to the edges of your furthest streaming cells:
// Within your Atmospheric Blueprint or Sky Controller:
// Ensure the Fog Inscattering Color matches the ambient light
// derived from your Sky Atmosphere component.
FogActor->VolumetricFog = true;
FogActor->VolumetricFogExtinctionDistance = 20000.0f; // Scale this to your map size
When you move through your World Partition grid, these systems remain globally persistent, meaning the atmospheric light transition stays smooth regardless of which streaming cell is currently loaded. By using the Sky Atmosphere as the master controller for both the fog and the clouds, you create a seamless transition where the horizon color logically matches the color of the scattered light in the fog.
Key Takeaway: Synchronizing your Sky Atmosphere, Volumetric Clouds, and Exponential Height Fog ensures that distant streaming cells are visually occluded by consistent light scattering, maintaining immersion across the entire expansive map.