Create a current in the Water System

To create and control a current in the water system, apply a current map to a water surface. A current map is a texture that modifies the local swell or agitation of a water surface current. Current maps are different from flow maps because the water flow can’t stop and it always has a direction.

To see a working current map, open the River sample scene.

Open the River sample scene

HDRP includes the River sample scene which shows how a current map behaves.

To open the River sample scene:

  1. Go to Window > Package Manager.
  2. Select High Definition RP.
  3. In the Samples tab, import the Environment Samples.
  4. Open the scene named River.

Create a current map texture

You can create a Current map texture in any image-editing software. The image can be in any non sRGB format. The resolution of a current map texture has a small impact on the current effect.

The Red and Green channels contain the 2D direction of the current and the Blue channel contains the influence of the current map. Black areas use the default direction, which is +X.

The following images display each channel of the current map included in the River sample scene.

  • The red channel of a current map:
  • The green channel of a current map:
  • The blue channel of a current map:

Create a current map texture in Krita

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The image-editing software Krita includes a brush type you can modify to author a current map:

  1. Open the Brush Editor.

  2. Select the arrow icon to open the Presets panel.

  3. In Engine, select Tangent Normal.

  4. Select the Texture Normal Map preset brush**.**

  5. In the General section, select Tangent Tilt.

  6. Set the Tangent Encoding properties to the following**:**

    1. Red: -X
    2. Green: -Y
    3. Blue: -Z

  8. In Tilt Options, select Direction.

  9. Select Save New Brush Preset.

This changes the color of the brush depending on the direction you draw in, allowing you to paint a current map.

Apply a current Map to a water surface

To set the current map a water surface uses:

  • Select a water surface to open its properties in the Inspector window
  • Open the Simulation section
  • In the Current Map property, select the picker (circle) and choose a texture to apply.

Current maps behave in a different way depending on the type of water surface:

  • Ocean: Set the current map in the Swell subsection. This affects properties in the First Band and Second Band subsections. In the Ripples subsection, you can change the Motion property to Inherit from Swell, or set a custom current map in the Swell subsection.
  • Rivers: Set the current map in the Agitation subsection. In the Ripples subsection, you can change the Motion property to Inherit from Agitation, or set a custom current map in the Agitation subsection.
  • Pools: You can only set a current map in the Ripples subsection.

Make an object follow a current map

When using Script Interactions to make an object float on the surface, you can get the current at the resulting location to make the object move with the flow of the water.

The River sample scene includes a script that extends the Float script to make objects float along the current map.

Debug a current map

To visualize the effect of a current map on a water surface:

  • Select a water surface to view its properties in the Inspector.
  • Open the Miscellaneous section.
  • Locate Debug Mode and select Current.