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Create simple clouds (Cloud Layer)
A Cloud Layer is a simple representation of clouds in the High Definition Render Pipeline (HDRP). The cloud layer is a 2D texture rendered on top of the sky that can be animated using a flowmap. You can also project cloud shadows on the ground.
Refer to Understand clouds for more information about clouds in the High Definition Render Pipeline (HDRP).
Using the Cloud Layer
The Cloud Layer uses the Volume framework, so to enable and modify Cloud Layer properties, you must add a Cloud Layer override to a Volume in your Scene. To add Cloud Layer to a Volume:
- In the Scene or Hierarchy view, select a GameObject that contains a Volume component to view it in the Inspector.
- In the Inspector, navigate to Add Override > Sky and click on Cloud Layer.
After you add a Cloud Layer override, you must set the Volume to use Cloud Layer. The Visual Environment override controls which type of clouds the Volume uses. In the Visual Environment override, navigate to the Sky section and set the Cloud Type to Cloud Layer. HDRP now renders a Cloud Layer for any Camera this Volume affects. To enable the Cloud Layer override, you must assign a cloud map. For information about the cloud map's format or how to find the example cloud map texture, see about the cloud map section.
The Cloud Layer will bake the cloud map to an intermediate texture, which is recomputed everytime a parameter changes. The resolution of the baked texture is determined by the Resolution parameter in the advanced settings of the inspector. Clouds shadows are also baked to a separate texture whose resolution is set by the Shadow Resolution parameter.
Refer to the Cloud Layer Volume Override reference for more information.
About the cloud map
The cloud map is a 2D RGBA texture in LatLong layout (sometimes called Cylindrical or Equirectangular) where each channel contains a cloud opacity. For rendering, HDRP mixes the four channels together using the Opacity RGBA parameters of the Volume override. This allows you to change the aspects of the clouds using a single texture and the volume framework. If you enable Upper Hemisphere Only, the map is interpreted as containing only the upper half of a LatLong texture. This means that clouds will only cover the sky above the horizon.
By default, HDRP uses a cloud map named DefaultCloudMap. This texture contains cumulus clouds in the red channel, stratus clouds in the green channel, cirrus clouds in the blue channel and wispy clouds in the alpha channel.
Note: This cloud map is formatted differently to the cloud map that the Volumetric Clouds feature uses.
Controlling cloud movement
The Cloud Layer override provides a way to move clouds at runtime, using a flowmap. A flowmap has the same layout as the [cloud map]create-simple-clouds-cloud-layer#about-the-cloud-map), in that it is a LatLong layout 2D texture, and also uses the Upper Hemisphere Only property to determine the area it affects.
A flowmap only uses the red and green channels and they represent horizontal and vertical displacement respectively. For each of these channels, a value of 0.5 means no displacement, a value of 0 means a negative displacement and a value of 1 means a positive displacement.