Water Body Actors

You can use Water Body Actors to define the location and shape of the water surface and their transitions in the level. Water bodies are made up of water mesh tiles that are managed by the Water Mesh Actor. This actor sets the quality and properties of all water bodies. You can set the water mesh actor up to cover the area where you want water bodies rendered. When you do so, Unreal Engine automatically generates the needed mesh. Rendering all the water bodies as a single water tile mesh allows for smooth and seamless transitions between them.

Water Bodies also determine wave movement and shading of the water surface, as well as the underwater post-processing. Each water body contains information about its depth and flow. You can query these for gameplay usage. For example, you can create physics interactions with the water's surface.

Types of Water Bodies

There are several types of Water Body Actors to choose from.

• Water Bodies for Oceans, Lakes, and Rivers. These are all defined using splines that store data about their type.
• A Custom type. This also has a spline for querying data, but you define the shape with a Static Mesh.
• An Island. This is used to raise landscape terrain within a defined spline area.
• An Exclusion Volume. You can use this to create underwater zones where gameplay can act as if it was not under water.

To add a Water Body Actor to your Level:

• Go to the Place Actors panel, select the Water Body Actor, and drag and drop it into your level

Water bodies automatically work with Landscape Terrain to carve out the terrain beneath them using a Landscape Brush. The Landscape Brush only edits the landscape layer when the Landscape has Enable Edit Layers checked.

Water Bodies include their own underwater post-processing that happens when the camera moves below the water's surface. This enables you to define the look of water with a subset of the standard post-process settings.

Ocean Water Body

The Ocean Water Body is defined by a closed loop spline that forms a shoreline and renders water out to a far distance from those spline points. The spline points all have the same height placement in the level.

Water Bodies are limited by how far they can reach, or their largest Extent Size. However, Ocean Water Bodies can reach this without completely filling the level, leaving a gap between the horizon line and the water depending on the perspective of the camera. Water Zone Actors provide an option to fill that gap with a simplified mesh and water material.

The example below demonstrates how the simplified water mesh can fill the empty space without the added cost of a highly tessellated mesh and complex material.

From an aerial perspective, it can be clear where the Ocean Water Body ends. You can use the Far Distance Mesh and match the color of its material to the Ocean Water Body to seamlessly fill the scene. This has less impact on performance.

The Far Distance Mesh is enabled by default in the Water Zone Actor. The Far Distance Mesh Extent is already set with a large enough distance to stretch to the world's edge.

To change the size of the extent:

• Go to the WaterZone Actor > Rendering > FarDistance, and change the value for Far Distance Mesh Extent.

By default, the Water_FarMesh material is assigned to the Far Distance Material slot. This material matches the default water materials used by the other water bodies ensuring that it will have a consistent look.

For consistency, when you adjust the color or other properties of your ocean water material, make sure to make the same changes to the Water_FarMesh material. Doing so ensures they blend together in the distance.

You can use Far Distance Mesh Extent to set how far (in world units) the Far Distance Mesh should extend beyond the Ocean Water Body. Make sure to use a large enough value that the mesh completely fills any gaps between the edge of the Ocean Water Body and the horizon line.

Lake Water Body

The Lake Water Body is defined by its closed loop, which forms the lake and carves out the landscape beneath it. Each of its spline points is limited to having all points reside at the same height, unlike river spline points.

River Water Body

The River Water Body is defined by its open spline with starting and ending points. Rivers carve out the landscape beneath them along the path of the spline. Rivers allow spline points to have varying heights. They do not drive surface motion using waves. Instead, rivers use velocity from the individual points along the spline to drive motion. The velocity is written to a flow map that visually drives the flow of water along the surface in the direction the spline is going.

River Water Bodies act as connections between other water bodies. At the points where lakes and oceans intersect a river, you can use a transitional material to automatically blend them together seamlessly.

Custom Water Body

The Water Body Custom uses a Static Mesh with the same water material used by other Water Bodies. It also uses the same meshing system with some added flexibility for customization, such as creating a water surface for a pool. The primary difference is that custom water bodies do not use the Water Mesh Actor and therefore do not automatically carve out the terrain. Custom water bodies can use a Wave Source from a Water Wave Asset and underwater post-processing.

Island Water Body

The Island Water Body creates islands based on a spline and includes similar terraforming controls to other water bodies. Their only purpose is to affect the landscape underneath them, to make sure that a given piece of land is always above water. Their terraforming is applied after all other water bodies.

Water Body Properties

All Water Bodies share core properties that make up the Water Body Component, but there are some settings specific to individual Water Body types.

Selected Points

The Selected Points category enables you to cycle through any of the currently selected Water Body's spline points. Each spline point has properties that include its location, rotation, and type. Some spline points also have Water Body-specific properties, such as Rivers having extra properties to define depth and width.

When a single or all spline points are selected, their properties are displayed below, showing their location, rotation, and type.

Each Water Body has its own Water category of settings that relate to the spline points. These include settings for the velocity and audio intensity. River Water Bodies also include settings for depth and river width. The Depth values are fed to the Curve controls of the water body.

River Spline Visualization and Manipulation

Water splines have the same features as generic splines. They have additional manipulators that you can enable through the right-click context menu.

• Visualize Water Velocity displays the velocity at each spline through a trio of arrows, which are scaled according to the velocity of the points.

  

• Visualize River Width displays two handles that you can select and drag to edit the width of river water bodies in the viewport.

  

• Visualize Depth displays an additional handle that you can select and drag to edit the depth within the viewport.

  

You can set a global scale in the Project Settings, under the Plugins > Water Editor settings.

Water

The Water category contains information about the selected Water Body. It also lists what Islands and Exclusion Volumes affect it. Under each of those categories, you can find the index number of the GPU-driven wave data.

This index is automatically used in the default Water_Material to calculate the correct surface waves. You can also manually set it to read from the parent material or any child instances through the scalar parameter called WaterBodyIndex.

Terrain

The Terrain category contains settings that change how the Water Body carves the terrain around the water.

For Water Bodies to interact with terrain, the Landscape must have Enable Edit Layers checked.

Curve Settings

The Curve Settings define the shape of the surface that is carved under the water, and primarily provides the water depth profile.

An Elevation Curve Asset is defined within a 0 to 1 range on both the X and Y axis. The Y axis represents the water's depth, and is multiplied with the Depth value set on each spline point. The default curve is a simple S curve that works for most cases.

The bottom-left corner of the curve is at 0,0. This is where the shoreline is located and the upper-right corner of the curve represents the maximum water depth.

For the Depth value that you set on River Water Body spline points to be accurate, you must keep the Y value at 1.

Water Heightmap Settings

Blend Mode

The Blend Mode provides a selection of modes that gives different results for how Water Bodies carve out the landscape terrain beneath them.

You can choose between Blend Modes called Alpha Blend, Min, Max, and Additive.

Most Water Bodies only need to use Alpha Blend, since it can both lower and raise the terrain to make sure a foundation exists at the height of the water.

The Min and Max options are ideally used in situations where you'd want to intersect a river with another water body without having the elevation of one affecting the other. For example, a river intersecting a lake should use a Min blend mode to prevent the river from raising the elevation inside the lake's carved-out terrain.

The Additive mode should be saved for special cases where you want to preserve the underlying detail since it does not ensure exact values are written to the landscape terrain.

Falloff Settings

The Falloff Settings determine how the Water Body carving blends into the existing terrain. You can customize this in several ways.

You can choose between two Falloff Modes called Angle and Width.

Angle-based falloff extends the object at a specified angle until an intersection with the landscape terrain occurs. Width-based falloff sets a fixed width that is used regardless of intersection with the landscape.

The Edge Offset applies a flat edge around the Water Body. This can be useful for flat shores on the sides of rivers, even when the river is carved through a mountain.

Effects

The Effects settings are a powerful sub-category of terrain carving settings. They provide controls to tweak the output and blending of a Water Body into the landscape terrain.

Blurring

The Blurring settings reduce artifacts that can occur during distance field generation. Such items come from aliasing due to texture resolution. A small amount of blurring is applied automatically, but you can increase or decrease the strength of the blurring by disabling Blur Shape and setting a custom Radius.

Curl Noise

The Curl Noise settings add procedural distortion to the Water Body's spline. It uses two octaves of curl noise, each with a separate tiling parameter and strength. By default, the curl noise is set to 0 and the effect is disabled.

The examples below have different Curl Amounts and Curl Tiling applied.

Smooth Blending

The Smooth Blending provides smoothing parameters for the inner and outer edges of a Water Body, which is useful for seamlessly blending into nearby terrain for player navigation.

The example below shows the effect of an increased Inner Smooth Distance and Outer Smooth Distance.

Terracing

Terracing applies steps to the terrain area affected by a Water Body. Terracing can be masked to only occur a specified distance away from the water's edge using an alpha range. Terraces can also be blended from sharp to smooth.

Below is an example of various terracing values for smoothness, spacing, and masking working together.

You can use the Mask Length and Mask Start Offset to adjust where the terracing starts within the falloff area.

Wave

The Wave section defines the waves of the selected Water Body. You can set the depth at which waves are attenuated, their max height bounds, and specify a Water Waves Asset used to drive Gerstner wave properties for a Water Body.

The Wave category contains the following:

Rendering

The Rendering category is where all Materials are applied to the Water Body, such as the surface material and the underwater post-process material. This section also contains common rendering properties found on all Actors and Components.

The properties table below covers water-related properties.

Not all properties are displayed that fall under the Rendering > Advanced category. Only the ones directly related to water bodies.

Water Bodies have their own default surface material and underwater post-process materials already assigned. You can create your own water materials for use with Water Bodies, but we recommend that you use the default water material as a starting point.

River Water Bodies contain two additional material assignment slots for transition materials for River to Lake and River to Ocean. These transition materials enable the seamless blending of rivers into other Water Body types that it connects to.

Below is an example of a River Water Body flowing into an Ocean Water Body with a transition material.

The Overlap Material Priority determines the priority given to that Water Body when it comes to generating water tiles. Higher valued priorities take precedence over others. When a Transition material is not applied to the River Water Body, this property is used to determine the precedence of the overlapping Water Body.

Underwater Post Process Settings

The Underwater Post Process Settings apply post-processing when the camera goes underwater.

Water Body Exclusion Volume

You can use Water Body Exclusion Volumes to create cavities in any kind of Water Body. This creates underwater zones where gameplay can act as if it was not underwater. For example, you could have an underwater base or tunnel where players can walk as normal.

Like Geometry Brushes, these volumes can be placed using the Place Actors panel. You can edit their shapes when the Level Editor has its Mode set to Brush Editing.

For Water Body Exclusion Volumes to work, you must set which Water Bodies they must ignore by choosing Exclude All Overlapping Water Bodies or by adding them to the Water Bodies to Exclude array.