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 water 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.

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

To use water exclusion, you need to enable it in the following locations:

  • Enable exclusion in a scene in the HDRP Asset:
  1. Select the HDRP Asset in the Project window.
  2. In the Inspector, go to Rendering > Water > Exclusion.
  3. Enable Exclusion.
  • Enable exclusion for all Cameras in the Frame Settings:
  1. Open the HDRP Global Settings.
  2. Go to the Frame Settings (Default Values) > Camera section.
  3. In the Rendering section, enable Water Exclusion.

To override the Frame Settings for an individual Camera:

  1. Click on a Camera in the Scene view or Hierarchy window to view its properties in the Inspector.
  2. Go to the Rendering section and enable Custom Frame Settings. This exposes the Frame Settings Overrides, which you can use to customize this Camera.
  3. In the Frame Setting Overrides section, open the Rendering drop-down
  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.