Vapor — Usage

1. Installation

Follow the Installation guide and add "Vapor" to your Build.cs dependencies.

2. Enable the Plugin

Open Edit → Plugins, search for Vapor, enable it, and restart the editor.

3. Place a Post Process Volume

Add a Post Process Volume to your level. Enable Infinite Extent (Unbound) for a global effect, or set a bounded volume for a localized fog zone.

4. Configure via Detail Panel

Select the Post Process Volume. In the Details panel, scroll to the Vapor category:

5. CVars (Console / INI)

All properties map to CVars. Use the console (~) or DefaultEngine.ini:

[/Script/Engine.RendererSettings]
r.Vapor.Enabled=1
r.Vapor.Density=0.3
r.Vapor.HeightFalloff=0.5
r.Vapor.PhaseG=0.6
r.Vapor.SkyGlowIntensity=1.0
r.Vapor.ResolutionScale=0.5
r.Vapor.RaymarchSteps=32

6. Blueprint API

// Get the subsystem
UVaporSubsystem* Vapor = GEngine->GetEngineSubsystem<UVaporSubsystem>();

// Adjust parameters at runtime
Vapor->SetDensity(0.5f);
Vapor->SetScatterColor(FLinearColor(1.f, 0.95f, 0.88f));
Vapor->SetPhaseG(0.7f);
Vapor->SetEnabled(true);

Blueprint nodes are available under the Vapor category in the node search.

7. Additional Light Sources

Vapor can incorporate up to 8 point/spot lights into the scattering computation. Register a light via Blueprint:

Vapor->RegisterScatterLight(MyPointLight);
Vapor->UnregisterScatterLight(MyPointLight);

Registered lights are uploaded to the constant buffer each frame; unregistered lights cost nothing.

8. Fog Volumes (Localized Fog)

Place an AVaporFogVolume actor in the level. The volume defines a box region with its own density override. Multiple volumes blend additively.