Exclude part of a water surface

Sometimes you might want to prevent water from appearing on top of other surfaces. For static environments, you can use a simulation mask to make sure the water stays under the terrain. For dynamic objects, it’s more practical to use a water excluder. A water excluder is a GameObject that marks pixels on screen that should not receive a water surface.

You can use a water excluder to remove a water surface inside a floating object. The following example shows a water excluder applied to the inside of a boat.

A water excluder applied to the inside of a boat.

This image shows the following, from left to right:

  • A boat with no water excluder. The water surface appears inside the boat and creates an artifact.
  • The water excluder used for this boat. It’s a custom mesh that fits the shape of the inside of the boat.
  • The boat with the water excluder inside it. This makes the water surface inside it invisible.

The water excluder is a child GameObject of the boat so that the excluder moves with the boat.

Note: A water excluder only affects the water surface from above. This means it does not exclude the underwater view of the surface.

Set up exclusion in your project

Water exclusion is enabled by default. For most projects, you don't need additional configuration.

To check water exclusion is enabled or to re-enable it, follow these steps:

  1. In the Project window, select the HDRP Asset.
  2. In the Inspector, go to Rendering > Water > Exclusion and verify that Exclusion is enabled.
  3. Go to Edit > Project Settings > Graphics > Pipeline Specific Settings > HDRP.
  4. In Frame Settings (Default Values) > Camera > Rendering, verify that Water Exclusion is enabled.

To override the Frame Settings for an individual Camera:

  1. In the Scene view or Hierarchy window, select a camera to view its properties in the Inspector window.
  2. In the Rendering section, enable Custom Frame Settings. Unity displays the Frame Settings Overrides section.
  3. In the Frame Settings Overrides section, open the Rendering dropdown.
  4. Enable Water Exclusion.

Create a water excluder

To add a water excluder to your scene go to GameObject > Water > Excluder. This adds a water excluder on a plane mesh. To change the shape of the water excluder:

  1. Click on the water excluder in the Scene view or Hierarchy window to view its properties in the Inspector.
  2. In the Mesh property, select the mesh picker (circle).
  3. Select the mesh you want to apply to this water excluder.

You can also right-click on a GameObject in the Hierarchy and select Water > Excluder to make the excluder copy the mesh of that GameObject.

Change the shape of a Water Excluder

If you want to exclude water from the inside of a boat, you will probably need to author a custom mesh that fits the shape of your boat. To do this, create a simplified version of the inside of your boat in a 3D modelling software, then assign the mesh to a Water Excluder object.