Oceanology Legacy - Underwater

🌊 Visual Effects

🎨 Post-Processing

💡 God Rays

Create immersive underwater environments with fog, caustics, god rays, and volumetric effects.

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Prerequisites

Requirement	Details
Engine	UE5.x (latest release)
Plugin	Oceanology Legacy installed and configured
Scene	Water body placed in your level
Lighting	A Directional Light (required for God Rays)

Underwater Modes

Oceanology Legacy offers two underwater rendering modes: Underwater (post-process based) and Volumetric Fog (volumetric rendering). Each has different visual characteristics and performance implications.

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Step-by-step

1. Open the Volumetric demonstration map

Oceanology Legacy includes a demonstration map that showcases underwater effects. In the Content Browser, navigate to: Plugins > Oceanology Legacy > Maps > Demonstration > Effects

Here you will find several demonstration levels:

• Mask_Map - Demonstrates underwater masking features.
• Mask_Map_Heightmap - Heightmap-based masking demonstration.
• RVT_Heightmap_Map - Runtime Virtual Texture heightmap features.
• RVT_Heightmap_Map_Heightmap - Combined RVT and heightmap demonstration.
• SoundOfWaves_Map - Audio features demonstration.
• Volumetric_Map - Underwater volumetric fog and effects demonstration.

Open Volumetric_Map to see a pre-configured underwater environment with all effects enabled. This is an excellent reference for understanding how the underwater systems work together.

2. Select the Underwater Mode

Select your BP_OceanologyInfiniteOcean actor and locate the Underwater category in the Details panel. The first setting is Underwater Mode, which determines how underwater rendering is handled.

Available Modes:

• None - Underwater effects are disabled. Use this for surface-only water or when you handle underwater rendering separately.
• Underwater - Post-process based underwater rendering. Provides good visual quality with moderate performance cost.
• Volumetric Fog - Volumetric rendering for more realistic light scattering and fog. Higher visual fidelity but increased performance cost.

Click the dropdown to select your preferred mode. The available settings will change based on your selection.

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Underwater Mode Configuration

3. Configure Underwater mode settings (Part 1)

With Underwater Mode set to Underwater, expand the Underwater subcategory to access all post-process parameters.

Atmosphere and Lighting:

• AtmosphereLighting - 25.0. Controls the intensity of atmospheric lighting underwater.
• SunPower - 6.0. Intensity of sunlight penetrating the water surface.
• UnderwaterLightDepth - 50000.0. Maximum depth where light is still visible.
• UnderwaterNoLightDepth - 100000.0. Depth at which complete darkness occurs.

Water Surface Band:

• Band Offset - 0.5. Vertical offset of the water surface band effect.
• Band Opacity - 1.0. Opacity of the surface band.
• Band Width - 1.0. Thickness of the surface transition band.

Depth and Fog:

• DarknessFadeDepth - 1.0. How quickly darkness increases with depth.
• DepthColorAbsorption - 1.5. Rate at which colors are absorbed underwater.
• FogDensity - 1.0. Overall density of underwater fog.
• LocalPosition - 0.0. Local offset for fog calculations.

Distortion:

• DistortionIntensity - 0.05. Strength of underwater visual distortion.
• DistortionScale - 0.5. Scale of the distortion pattern.
• DistortionSpeed - 0.25. Animation speed of distortion.

Vignette:

• VignetteDark - 1.5. Darkness intensity at screen edges.
• VignetteDistortion - 0.05. Distortion amount in vignette area.
• VignetteEdge - 1.0. Sharpness of vignette edge.

Water Line:

• WaterLineColorIntensity - 4.0. Color intensity at the water surface line.
• WaterLineDistanceFalloff - -0.015. Falloff rate for water line effect.
• WaterLineRefraction - 0.005. Refraction amount at water line.
• WaterLineRefractionWidth - 0.5. Width of refraction zone.

Wet Effect:

• Wet Alpha - 0.2. Opacity of wet screen effect when exiting water.

4. Configure Underwater mode settings (Part 2)

Scroll down to find additional underwater settings including wet effects, colors, and masking options.

Wet Effect Settings:

• Wet Hardness - 0.25. Sharpness of wet droplet edges.
• Wet Location - 0.0. Position offset for wet effect.
• Wet Radius - 1.0. Size of wet effect coverage.

Exponential Fog Colors:

• ExponentialFogColorHigh - Blue color for shallow underwater fog.
• ExponentialFogColorLow - Darker blue for deep underwater fog.

Scene Colors:

• SceneColorDeep - Color tint applied at maximum depth.
• SceneColorShallow - Color tint applied near the surface.

Distortion Texture:

• DistortionTexture - WindTurbulenceVectorAndIntensity. The texture used for underwater distortion animation.

Mask Underwater:

• UnderwaterLandscapeMask - 1.0. Mask intensity for landscape geometry.
• UnderwaterObjectMask - 1.0. Mask intensity for object geometry.
• User Override Underwater - Checkbox to enable custom underwater material override.

Materials:

• Underwater Material - M_UnderOcean_PostProc. The post-process material used for underwater rendering.
• Volumetric Fog Material - None. Not used in standard Underwater mode.

5. Configure God Rays, Volumetric Fog, and Bubbles

Continue scrolling to find the advanced effect settings that work with both underwater modes.

God Rays: This section is collapsed by default. God Rays require a Light Function on your Directional Light (covered in steps 9-10).

Volumetric Fog:

• MultiScatteringContribution - 2000.0. Contribution of multiple scattering to fog appearance.
• MultiScatteringOcclusion - 1000.0. Occlusion factor for scattered light.
• Wet Alpha - 0.5. Wet effect opacity for volumetric mode.
• ExponentialFogColor - Blue color for volumetric fog.

Bubbles Settings:

• Enable Bubbles - Enabled. Toggle underwater bubble particles.
• Bubble Spawn Count - 1000. Number of bubbles to spawn.
• Bubble Speed - 1.0. Rising speed of bubbles.
• Bubbles Material - M_OceanBubbles_Inst. Material instance for bubble rendering.
• Bubbles Effect - NS_OceanBubblesUnderwater. Niagara system for bubble particles.

Default:

• ReloadSettings - Button to reset all underwater settings to defaults.

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Volumetric Fog Mode Configuration

6. Configure Volumetric Fog mode

Change Underwater Mode to Volumetric Fog for more realistic light scattering and atmospheric effects.

When Volumetric Fog mode is selected, the settings panel changes to show volumetric-specific options:

Mask Underwater:

• User Override Underwater - Checkbox to enable custom material override.

Materials:

• Underwater Material - M_UnderOcean_PostProc. Post-process material for screen effects.
• Volumetric Fog Material - M_UnderOcean_Volumetric. Material that renders the volumetric fog.

God Rays: Collapsed section for god ray configuration (requires Light Function setup).

Volumetric Fog:

• MultiScatteringContribution - 2000.0. Controls how much multiple scattering contributes to the fog appearance. Higher values create denser, more atmospheric fog.
• MultiScatteringOcclusion - 1000.0. Controls light occlusion from scattered rays.
• Wet Alpha - 0.5. Opacity of wet screen effect.
• ExponentialFogColor - The color of the volumetric fog (blue by default).

Volumetric Fog mode provides more physically accurate light behavior but requires more GPU resources than the standard Underwater mode.

7. Configure Bubbles in Volumetric Fog mode

The Bubbles Settings work identically in both underwater modes. With Volumetric Fog selected, scroll down to configure bubble particles.

Bubbles Settings:

• Enable Bubbles - Enabled. Toggle to enable or disable underwater bubble particles.
• Bubble Spawn Count - 1000. Total number of bubble particles in the system. Increase for denser bubble fields, decrease for performance.
• Bubble Speed - 1.0. Multiplier for bubble rising velocity. Values above 1.0 make bubbles rise faster.
• Bubbles Material - M_OceanBubbles_Inst. The material instance used to render bubble particles. You can create custom materials for stylized bubbles.
• Bubbles Effect - NS_OceanBubblesUnderwater. The Niagara particle system that spawns and animates bubbles.

Bubbles add significant visual interest to underwater scenes. They respond to camera movement and create a sense of being submerged in water.

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Caustics Configuration

8. Configure Caustics for underwater rendering

Caustics create the characteristic light patterns seen underwater. Select your BP_OceanologyInfiniteOcean actor and search for caustics in the Details panel search box.

Preset Inclusion Groups:

• Preset Inclusion Groups - 25 Array elements. Defines which presets include caustics.
• Index [1] - Caustics. Ensures caustics are included in the preset system.

Caustics Parameters:

• CausticsBrightness - 10.0. Overall brightness of caustic light patterns.
• CausticsFadeInDistance - 1000.0. Distance over which caustics fade in.
• CausticsScale - 16.0. Size of the caustic pattern texture.
• FadeDistance - 1.0. How quickly caustics fade with depth.
• LightParallax - 1.0. Parallax effect for caustic light rays.
• MultiplyRefraction - 1.333. Refraction multiplier (matches water IOR).
• T_Caustics - T_Caustics. The texture used for caustic patterns.

These settings affect how caustics appear both on underwater surfaces and when viewed from below the water surface.

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God Rays Setup

God Rays create dramatic shafts of light penetrating the water surface. This requires assigning a Light Function material to your scene's Directional Light.

9. Locate the God Rays materials

In the Content Browser, navigate to: Plugins > Oceanology Legacy > Design > Ocean > Materials > LightFunction > CausticsDL

Here you will find two assets:

• M_DirectionalCausticsGodRays - The master material for god ray caustics.
• MI_DirectionalCausticsGodRays - A material instance ready to use. Use this one.

The material instance is pre-configured with optimal settings. You can duplicate it if you need custom god ray variations for different scenes.

10. Assign Light Function to Directional Light

Select your Directional Light actor in the scene. In the Details panel, search for lightfunction to filter the settings.

Light Function Settings:

• Light Function Material - MI_DirectionalCausticsGodRays. Assign the material instance from step 9.
• Light Function Scale - 1024.0, 1024.0, 1024.0. Scale of the light function projection. Larger values spread the pattern over more area.
• Fade Distance - 100000.0. Distance at which the light function fades out completely.

Once configured, god rays will appear as animated light shafts when the camera is underwater. The rays follow the directional light angle and create realistic caustic patterns on underwater surfaces.

Tips:

• Ensure your Directional Light has Cast Shadows enabled for best results.
• Adjust Light Function Scale based on your scene scale.
• The Fade Distance should be larger than your maximum underwater view distance.

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Exponential Height Fog Configuration

11. Enable Volumetric Fog on ExponentialHeightFog actor

Critical step for Volumetric Fog mode: If you selected Volumetric Fog as your Underwater Mode but the volumetric effect is not visible underwater, you need to enable Volumetric Fog on your scene's ExponentialHeightFog actor.

Select the ExponentialHeightFog actor in the Outliner (e.g., Darkworld_ExponentialHeightFog). In the Details panel, locate the Volumetric Fog category:

Volumetric Fog Settings:

Property	Value	Explanation
Volumetric Fog	✅ Enabled	Must be enabled for underwater volumetric fog to render. Without this, the Volumetric Fog underwater mode will not display any fog effect.

Why this is required:

Unreal Engine's volumetric fog system is controlled globally by the ExponentialHeightFog actor. Oceanology's underwater Volumetric Fog mode integrates with this system — it doesn't create its own independent volumetric rendering. If the scene's ExponentialHeightFog has Volumetric Fog disabled, there's no volumetric system for Oceanology to inject underwater fog into.

Troubleshooting:

• If underwater appears clear with no fog when using Volumetric Fog mode → Check ExponentialHeightFog actor
• If you don't have an ExponentialHeightFog in your scene → Add one and enable Volumetric Fog
• If Volumetric Fog is too dense/sparse above water → Adjust ExponentialHeightFog parameters, Oceanology handles underwater separately

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Underwater Mode Comparison

The following table compares the two underwater rendering modes:

Aspect	Underwater Mode	Volumetric Fog Mode
Rendering Method	Post-process	Volumetric rendering
Visual Quality	Good	Excellent
Performance Cost	Moderate	Higher
Light Scattering	Approximated	Physically-based
Fog Density Control	Basic	Advanced (MultiScattering)
Best For	Mobile, performance-critical	PC, cinematic quality
God Rays Support	✅ Yes	✅ Yes
Bubbles Support	✅ Yes	✅ Yes
Caustics Support	✅ Yes	✅ Yes

Recommendations:

• Use Underwater mode for:

  • Mobile or lower-end hardware
  • Scenes where underwater is secondary
  • Projects prioritizing performance

• Use Volumetric Fog mode for:

  • PC and console projects
  • Cinematic underwater sequences
  • Games focused on underwater exploration
  • Scenes requiring realistic light behavior

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Underwater Settings Reference

Category	Parameter	Default	Effect
Lighting	AtmosphereLighting	25.0	Atmospheric light intensity
Lighting	SunPower	6.0	Sunlight penetration strength
Depth	UnderwaterLightDepth	50000.0	Light visibility depth
Depth	UnderwaterNoLightDepth	100000.0	Complete darkness depth
Fog	FogDensity	1.0	Underwater fog thickness
Fog	DepthColorAbsorption	1.5	Color absorption rate
Distortion	DistortionIntensity	0.05	Visual distortion strength
Vignette	VignetteDark	1.5	Edge darkening intensity
Water Line	WaterLineColorIntensity	4.0	Surface line visibility
Bubbles	Bubble Spawn Count	1000	Number of bubble particles
Volumetric	MultiScatteringContribution	2000.0	Fog scattering amount
Caustics	CausticsBrightness	10.0	Light pattern intensity

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Troubleshooting Common Issues

Problem	Likely Cause	Solution
No underwater effect visible	Underwater Mode set to None	Change Underwater Mode to Underwater or Volumetric Fog
Volumetric fog not visible underwater	ExponentialHeightFog Volumetric Fog disabled	Enable Volumetric Fog on scene's ExponentialHeightFog actor
Underwater too dark	SunPower or AtmosphereLighting too low	Increase SunPower and AtmosphereLighting values
Underwater too bright	UnderwaterLightDepth too high	Reduce UnderwaterLightDepth or increase DepthColorAbsorption
No god rays visible	Light Function not assigned	Assign MI_DirectionalCausticsGodRays to Directional Light
God rays not animating	Material not properly connected	Verify Light Function Material is the material instance, not the master
No bubbles appearing	Enable Bubbles disabled	Enable bubbles in Bubbles Settings
Bubbles too sparse	Bubble Spawn Count too low	Increase Bubble Spawn Count
Heavy distortion	DistortionIntensity too high	Reduce DistortionIntensity to 0.02-0.05
Performance issues	Volumetric Fog mode on weak hardware	Switch to standard Underwater mode
Water line not visible	WaterLineColorIntensity too low	Increase WaterLineColorIntensity

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Summary

In this guide, you learned how to:

1. Explore demonstration maps - Open the Volumetric_Map to see pre-configured underwater effects.
2. Select Underwater Mode - Choose between None, Underwater, or Volumetric Fog rendering modes.
3. Configure Underwater mode - Set up post-process based underwater with lighting, fog, distortion, and vignette.
4. Configure Volumetric Fog mode - Enable physically-based light scattering for realistic underwater rendering.
5. Enable Bubbles - Add animated bubble particles using the Niagara system.
6. Set up Caustics - Configure underwater light patterns for realistic illumination.
7. Enable God Rays - Assign Light Function materials to your Directional Light for dramatic light shafts.
8. Enable ExponentialHeightFog Volumetric Fog - Required for Volumetric Fog underwater mode to render properly.

With these settings, you can create immersive underwater environments ranging from bright tropical shallows to dark ocean depths.