System architecture

Dynamic Volumetric Sky is one Blueprint actor with a lot of exposed parameters. Knowing how the system thinks makes it much faster to find the right setting.

One source of truth

All time, weather, lighting, and atmosphere is driven by the single BP_DynamicVolumetricSky actor placed in your level. Selecting it shows the full Details panel of everything you can tune.

There is no separate “weather actor” or “atmosphere actor”. The directional light, sky light, sky atmosphere, exponential height fog, volumetric clouds, and any post-process work the sky needs are all spawned, owned, and updated by this one actor. That is also why Quick Start step 1 insists you remove every default lighting and atmosphere actor before placing the system: anything you leave in the level competes with the actor that owns the simulation.

Three runtime modes

System Mode is the first decision. It changes how time and weather progress and how state is shared.

Mode	What it does
Single Player	Runs locally, optimized for one camera. Use this for offline games.
Multiplayer	Replicates time and weather from server to clients so everyone sees the same sky. Use this for any networked game.
Sequencer Mode	For cinematic renders. Disables runtime randomness so frames are deterministic across re-renders. Use this when rendering through Movie Render Queue.

Tip

If you flip a multiplayer game to Single Player for testing, expect the clients to drift apart in seconds. Each instance runs its own simulation in that mode.

Read-only weather state

A handful of values are computed by the simulation, not set by you:

• Current Weather on Display
• Sunrise, Sunset (decimal hours, so 6.67 means 06:40)
• Atmospheric Pressure, with Pressure Unit
• Temperature, with Temperature Unit
• Humidity
• Precipitation Chance
• Wind Direction, Wind Speed, with Wind Speed Unit

You read these. They are useful for HUDs and game logic (spawn ice on cold days, slow movement in heavy wind, expose temperature on a UI panel, and so on). They are also surfaced on the in-game UI widget out of the box.

Configurable units

Temperature can show in °C, K, or °F. Pressure in hPa, Psi, or Atm. Wind in km/h, mph, m/s, or ft/s. Pick whatever your game’s UI prefers; the underlying simulation is unit-agnostic.

Where to next

• Periods and blending: why the system thinks in four key poses
• Weather states: the ten states and what drives transitions
• Indoor occlusion: how the system detects “covered” and switches lighting