Riverology — Underwater
Last updated: 2025-12-09
Prerequisites
- Unreal Engine 5.6 or newer.
- Riverology installed and configured (see the Setup page).
- At least one BP_Riverology river spline placed in your level.
- Basic understanding of post-processing and fog systems in Unreal Engine.
Notes
- The Underwater settings in Riverology control the visual appearance when the camera submerges beneath the river surface. These parameters define fog density, light absorption, color tinting, and surface effects that create a realistic underwater experience.
- The system automatically detects when the camera enters the water volume and applies the configured post-processing effects.
- Properly tuned underwater settings are essential for immersive swimming gameplay and underwater exploration sequences.
Step-by-step
1. Configure the Underwater parameters
Select BP_Riverology in your scene and scroll through the Details panel to find the Underwater category. This section contains all parameters that control the underwater visual experience:
Fog Settings:
- Enable Fog — ✅ Enables underwater fog rendering.
- Light Absorption — Controls how quickly light diminishes with depth (default: 5.0). Higher values create darker, murkier water.
- Fog Scatter Color — The color of light scattered by particles in the water.
- Fog Ambient Color — The ambient fog color that fills the underwater environment.
- Absorption — The color absorbed by the water, affecting the overall tint.
- Fog — Fog density value (default: 0.005). Higher values reduce visibility distance.
Surface Band Settings:
- Band Color — The color of the surface band visible from underwater.
- Band Width — Width of the surface transition band (default: 2.0).
- Band Offset — Vertical offset of the band effect (default: 1.0).
- Band Opacity — Opacity of the surface band (default: 1.0).
Scattering and Wet Effects:
- Scattering Aniso — Anisotropy of light scattering underwater (default: 0.75).
- Wet Location — Position reference for wet effects (default: 0.0).
- Wet Hardness — Sharpness of the wet/dry transition (default: 0.15).
- Wet Radius — Radius of wet effect application (default: 3.0).
- Wet Alpha — Opacity of wet surface effects (default: 0.2).
Depth Settings:
- Max Depth — Maximum depth for underwater calculations (default: 45000.0).
2. Preview the underwater environment
Press Play and submerge the camera beneath the river surface to observe how your Underwater settings affect the visual experience.
Key visual elements:
- Fog density — How quickly distant objects fade into the fog color.
- Color absorption — The overall tint and mood of the underwater environment.
- Surface visibility — The band effect visible when looking up toward the surface.
- Light behavior — How light rays penetrate and scatter through the water.
The image shows a typical underwater view with fog absorption creating depth, the riverbed visible below, and the water surface with refraction effects visible above.
Parameter Reference
| Parameter | Default | Description |
|---|---|---|
| Enable Fog | true | Enables underwater fog rendering |
| Light Absorption | 5.0 | Light falloff rate with depth |
| Fog Scatter Color | — | Color of scattered light particles |
| Fog Ambient Color | — | Ambient fill color underwater |
| Absorption | — | Water color absorption tint |
| Band Color | — | Surface band color from below |
| Band Width | 2.0 | Surface transition band width |
| Band Offset | 1.0 | Vertical band position offset |
| Band Opacity | 1.0 | Surface band visibility |
| Scattering Aniso | 0.75 | Light scattering directionality |
| Wet Location | 0.0 | Wet effect position reference |
| Wet Hardness | 0.15 | Wet/dry transition sharpness |
| Wet Radius | 3.0 | Wet effect coverage radius |
| Wet Alpha | 0.2 | Wet effect opacity |
| Max Depth | 45000.0 | Maximum underwater depth |
| Fog | 0.005 | Fog density multiplier |
Recommended Presets
| Water Type | Light Absorption | Fog | Scattering Aniso | Notes |
|---|---|---|---|---|
| Clear River | 3.0 | 0.002 | 0.8 | High visibility, light tint |
| Murky River | 8.0 | 0.015 | 0.6 | Low visibility, green/brown tint |
| Deep Pool | 6.0 | 0.008 | 0.75 | Moderate visibility, blue tint |
| Swamp | 10.0 | 0.025 | 0.5 | Very low visibility, dark green |
Troubleshooting Common Issues
| Problem | Likely Cause | Solution |
|---|---|---|
| No underwater effect | Enable Fog disabled | Enable the Enable Fog checkbox |
| Too dark underwater | Light Absorption too high | Reduce Light Absorption value |
| Can't see anything | Fog value too high | Reduce Fog density value |
| Unrealistic color | Absorption color incorrect | Adjust Absorption and Fog colors |
| Surface band not visible | Band Opacity too low | Increase Band Opacity |
| Harsh surface transition | Band Width too small | Increase Band Width value |
| Wet effects too strong | Wet Alpha too high | Reduce Wet Alpha value |
Summary
In this guide, you learned how to:
- Configure underwater fog — Set up fog density, absorption, and scatter colors for realistic depth perception.
- Adjust surface band effects — Control the visual transition when looking at the surface from below.
- Fine-tune wet effects — Configure the wet surface appearance parameters.
These settings create the immersive underwater experience essential for swimming gameplay and underwater exploration in your Riverology rivers.