Cloud Layer
The Cloud Layer Volume component override controls settings relevant to rendering 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.
This component also exposes an option to project cloud shadows on the ground.
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.
API
To access and control this override at runtime, use the Volume scripting API. Because of how the Volume system works, you edit properties in a different way to standard Unity components. There are also other nuances to be aware of too, such as each property has an overrideState. This indicates to the Volume system whether to use the property value you set, or use the default value stored in the Volume Profile. For information on how to use the API correctly, see Volume scripting API.
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, 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.
Properties
To edit properties in any Volume component override, enable the checkbox to the left of the property. This also tells HDRP to use the property value you specify for the Volume component rather than the default value. If you disable the checkbox, HDRP ignores the property you set and uses the Volume’s default value for that property instead.
| Property | Description |
|---|---|
| Opacity | The global opacity of the cloud layer. A value of 0 makes clouds completely transparent. |
| Upper Hemisphere Only | Indicates whether the Cloud Layer exclusively renders above the horizon or not. When enabled, HDRP still uses the entire Cloud Map texture, but the clouds will be renderer above the horizon. |
| Layers | The number of cloud layers to render. Each layer has its own set of properties. The options are: • 1: Renders a single cloud layer. • 2: Renders two cloud layers. |
| Resolution | The resolution of the texture HDRP uses to bake the clouds. |
Per-layer
The Inspector shows the following properties for each cloud layer. The Layers property determines the number of cloud layers to render.
| Property | Description |
|---|---|
| Cloud Map | Assign a Texture that HDRP uses to render the cloud layer. For more information about the cloud map, see about the cloud map. |
| - Opacity R | The opacity multiplier to apply to the Cloud Map's red channel. |
| - Opacity G | The opacity multiplier to apply to the Cloud Map's green channel. |
| - Opacity B | The opacity multiplier to apply to the Cloud Map's blue channel. |
| - Opacity A | The opacity multiplier to apply to the Cloud Map's alpha channel. |
| Altitude | The altitude of the Cloud Layer in meters, used to calculate the sun light attenuation. |
| Rotation | The angle to rotate the Cloud Layer texture by, in degrees. |
| Tint | The color HDRP uses to tint the clouds. |
| Exposure Compensation | The exposure compensation of the clouds in EV relative to the main directional Light. |
| Wind | Specifies the method HDRP uses to simulate wind. • None: No wind. • Horizontal: HDRP distorts the clouds using a uniform horizontal wind direction. • Flowmap: HDRP distorts the clouds using the Flowmap texture. |
| - Orientation | The orientation of the wind relative to the X world vector (in degrees). This value can be relative to the Global Wind Orientation defined in the Visual Environment. |
| - Speed | The wind speed in kilometers per hour. This value can be relative to the Global Wind Speed defined in the Visual Environment. |
| - Flowmap | The flowmap HDRP uses to distort UVs when rendering the clouds. For more information about the flowmap, see controlling cloud movement. This property only appears when you select Flowmap from the Distortion drop-down. |
| Raymarching | Indicates whether HDRP calculates lighting for the clouds using the main directional light. When enabled, HDRP uses 2D raymarching on the Cloud Map to approximate self-shadowing from the sun light. The lighting computations are baked inside a texture and only recomputed when any of the relevant parameter changes. |
| - Steps | The number of raymarching steps HDRP uses to calculate lighting for the clouds. The higher the value, the greater the travelled distance is. |
| - Density | The density of the clouds. The larger the value, the darker the clouds will appear. |
| - Ambient Probe Dimmer | Controls the influence of the ambient probe on the cloud layer volume. A lower value will suppress the ambient light and produce darker clouds overall. |
| Cast Shadows | Indicates whether clouds cast shadows for the main directional light. This calculates the shadow texture and sets it as the light cookie for the main direction Light. |
| Shadows Property | Description |
|---|---|
| Shadow Multiplier | The opacity of the cloud shadows. The higher the value, the darker the shadows. |
| Shadow Tint | The tint HDRP applies to the cloud shadows. |
| Shadow Resolution | The resolution of the cloud shadows texture. |
| Shadow Size | The size of the projected cloud shadows. |