127 lines
16 KiB
Markdown
127 lines
16 KiB
Markdown
# Volumetric Clouds Volume Override reference
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The Volumetric Clouds Volume Override lets you configure how HDRP renders volumetric clouds.
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Refer to [Create realistic clouds (volumetric clouds)](create-realistic-clouds-volumetric-clouds.md) for more information.
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## Properties
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### General
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| **Property** | **Description** |
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| ------------ | ----------------------------------------------------- |
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| **State** | When set to **Enabled**, HDRP renders volumetric clouds. |
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### Shape
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| **Property** | **Description** |
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| --------------------------------- | ------------------------------------------------------------ |
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| **Cloud Control** | Specifies the mode to control volumetric cloud properties. The options are:<br/>• **Simple**: Uses sliders and input fields to customize volumetric cloud shape properties. This mode generates a cloud map from the various properties and uses HDRP's internal cloud lookup table.<br/>• **Advanced**: Uses separate Textures to specify each cloud type and their coverage. This mode generates a cloud map from the various Textures and uses HDRP's internal cloud lookup table.<br/>• **Manual**: Uses the cloud map and lookup table you supply to render the clouds. For more information on the cloud map and cloud lookup table, see [Cloud map and cloud lookup table](#cloud-map-and-cloud-lookup-table). |
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| - **Cloud Preset** | Specifies the preset to apply to the **Simple** mode properties. The options are: <br/>• **Sparse**: Smaller clouds that are spread apart.<br/>• **Cloudy**: Medium-sized clouds that partially cover the sky.<br/>• **Overcast**: A light layer of cloud that covers the entire sky. Some areas are less dense and let more light through, whereas other areas are more dense and appear darker.<br/>• **Storm Clouds**: Large dark clouds that cover most of the sky.<br/>• **Custom**: Exposes properties that control the shape of the clouds. <br/><br/>This property only appears if you set **Cloud Control** to **Simple**. |
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| - **Density Curve** | Controls the density (Y axis) of the volumetric clouds as a function of the height (X Axis) inside the cloud volume. <br/><br/>This property only appears if you set **Cloud Control** to **Simple**.|
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| - **Erosion Curve** | Controls the erosion (Y axis) of the volumetric clouds as a function of the height (X Axis) inside the cloud volume. <br/><br/>This property only appears if you set **Cloud Control** to **Simple**.|
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| - **Ambient Occlusion Curve** | Controls the ambient occlusion (Y axis) of the volumetric clouds as a function of the height (X Axis) inside the cloud volume. <br/><br/>This property only appears if you set **Cloud Control** to **Simple**.|
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| - **Cumulus Map** | Specifies a Texture that defines the distribution of clouds in the lower layer. <br/><br/>This property only appears if you set **Cloud Control** to **Advanced**. |
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| - **Cumulus Map Multiplier** | The multiplier for the clouds specified in the **Cumulus Map**. A value of **0** completely hides the cumulus clouds. <br/><br/>This property only appears if you set **Cloud Control** to **Advanced**. |
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| - **Alto Stratus Map** | Specifies a Texture that defines the distribution of clouds in the higher layer. <br/><br/>This property only appears if you set **Cloud Control** to **Advanced**. |
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| - **Alto Stratus Map Multiplier** | The multiplier for the clouds specified in the **Alto Stratus Map**. A value of **0** completely hides the alto stratus clouds. <br/><br/>This property only appears if you set **Cloud Control** to **Advanced**. |
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| - **Cumulonimbus Map** | Specifies a Texture that defines the distribution of anvil shaped cumulonimbus clouds. <br/><br/>This property only appears if you set **Cloud Control** to **Advanced**. |
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| - **Cumulonimbus Map Multiplier** | The multiplier for the clouds specified in the **Cumulonimbus Map**. A value of **0** completely hides the cumulonimbus clouds. <br/><br/>This property only appears if you set **Cloud Control** to **Advanced**. |
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| - **Rain Map** | Specifies a Texture that defines the distribution of rain in the clouds. <br/><br/>This property only appears if you set **Cloud Control** to **Advanced**. |
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| - **Cloud Map Resolution** | Specifies the resolution for the internal Texture HDRP uses for the cloud map. A lower resolution produces better performance, but less precise cloud type transitions. <br/><br/>This property only appears if you set **Cloud Control** to **Advanced**. |
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| - **Cloud Map** | Specifies the cloud map to use for the volumetric clouds. For information on the format of this Texture, see [Cloud map and cloud lookup table](#cloud-map-and-cloud-lookup-table). <br/><br/>This property only appears if you set **Cloud Control** to **Custom**. |
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| - **Cloud LUT** | Specifies the lookup table for the clouds. For information on the format of this Texture, see [Cloud map and cloud lookup table](#cloud-map-and-cloud-lookup-table). <br/><br/>This property only appears if you set **Cloud Control** to **Custom**. |
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| - **Cloud Map Tiling** | The **X** and **Y** UV tile rate for one or more cloud map Textures. HDRP uses the **X** and **Y** values to tile the clouds across the sky. When modifying those properties, cloud position is only maintained at the origin of the world (0,0,0). <br/>If **Cloud Control** is set to **Advanced**, this affects **Cumulus Map**, **Alto Stratus Map**, **Cumulonimbus Map**, and **Rain Map**.<br/>If **Cloud Control** is set to **Custom**, this affects the Texture assigned to the **Cloud Map** property.<br/><br/>This property only appears if you set **Cloud Control** to **Advanced** or **Custom**. |
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| - **Cloud Map Offset** | The **X** and **Y** UV offset for one or more cloud map Textures. HDRP uses the **X** and **Y** values to offset the clouds across the sky.<br/>If **Cloud Control** is set to **Advanced**, this affects **Cumulus Map**, **Alto Stratus Map**, **Cumulonimbus Map**, and **Rain Map**.<br/>If **Cloud Control** is set to **Custom**, this affects the Texture assigned to the **Cloud Map** property.<br/><br/>This property only appears if you set **Cloud Control** to **Advanced** or **Custom**, or if you set it to **Simple** and then set **Cloud Preset** to **Custom**. |
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| - **Density Multiplier** | The global density of the volumetric clouds. <br/><br/>This property only appears if you set **Cloud Control** to **Advanced** or **Custom**, or if you set it to **Simple** and then set **Cloud Preset** to **Custom**. |
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| - **Shape Factor** | Controls the amount of shaping to apply to the cloud volume. A higher value produces less cloud coverage and smaller clouds. <br/><br/>This property only appears if you set **Cloud Control** to **Advanced** or **Custom**, or if you set it to **Simple** and then set **Cloud Preset** to **Custom**. |
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| - **Shape Scale** | Controls the size of the noise HDRP uses in the shaping stage to generate the general cloud shapes. <br/><br/>This property only appears if you set **Cloud Control** to **Advanced** or **Custom**, or if you set it to **Simple** and then set **Cloud Preset** to **Custom**. |
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| - **Shape Offset X** | Controls the offset (world X-axis) applied when evaluating the larger noise passing through the cloud coverage. The values "0", "-1" and "1" will give the same result. |
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| - **Shape Offset Y** | Controls the offset (world Y-axis) applied when evaluating the larger noise passing through the cloud coverage. The values "0", "-1" and "1" will give the same result. |
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| - **Shape Offset Z** | Controls the offset (world Z-axis) applied when evaluating the larger noise passing through the cloud coverage. The values "0", "-1" and "1" will give the same result. |
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| - **Erosion Factor** | Controls the amount of erosion to apply on the edge of the clouds. A higher value erodes clouds more significantly. <br/><br/>This property only appears if you set **Cloud Control** to **Advanced** or **Custom**, or if you set it to **Simple** and then set **Cloud Preset** to **Custom**. |
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| - **Erosion Scale** | Controls the size of the noise HDRP uses in the erosion stage to add local details to the cloud edges. <br/><br/>This property only appears if you set **Cloud Control** to **Advanced** or **Custom**, or if you set it to **Simple** and then set **Cloud Preset** to **Custom**. |
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| **Bottom Altitude** | Controls the altitude of the bottom of the volumetric clouds volume in meters.|
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| **Altitude Range** | Controls the size of the volumetric clouds volume in meters. |
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| **Fade In Mode** | Controls the mode in which the clouds fade in when close to the camera's near plane.|
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| **Fade In Start** | Controls the minimal distance at which clouds start appearing.|
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| **Fade In Distance** | Controls the distance that it takes for the clouds to reach their complete density.|
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### Wind
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| **Property** | **Description** |
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| -------------------------------- | ------------------------------------------------------------ |
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| **Global Horizontal Wind Speed** | Sets the global horizontal wind speed in kilometers per hour.<br />This value can be relative to the **Global Wind Speed** defined in the **Visual Environment**. |
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| - **Orientation** | Controls the orientation of the wind relative to the world-space direction x-axis.<br />This value can be relative to the **Global Wind Orientation** defined in the **Visual Environment**. |
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| - **Cloud Map Speed Multiplier** | The multiplier to apply to the speed of the cloud map. |
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| - **Shape Speed Multiplier** | The multiplier to apply to the speed of larger cloud shapes. |
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| - **Erosion Speed Multiplier** | The multiplier to apply to the speed of erosion cloud shapes. |
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| **Vertical Shape Wind Speed** | Controls the vertical wind speed of the larger cloud shapes. |
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| **Vertical Erosion Wind Speed** | Controls the vertical wind speed of the erosion cloud shapes. |
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### Quality
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| **Property** | **Description** |
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| -------------------------------- | ------------------------------------------------------------ |
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| **Temporal Accumulation Factor** | The amount of temporal accumulation to apply to the clouds. Temporal accumulation increases the visual quality of clouds by decreasing the noise. A higher value produces better quality clouds, but can create [ghosting](Glossary.md#ghosting). |
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| **Ghosting Reduction** | When you enable this property, HDRP removes the ghosting caused by temporal accumulation. This effect might cause a flickering effect when the **Temporal Accumulation Factor** value is low. |
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| **Num Primary Steps** | The number of steps to use to evaluate the clouds' transmittance. Higher values linearly increase the resource intensity of the effect. |
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| **Num Light Steps** | The number of steps to use to evaluate the clouds' lighting. Higher values exponent increase the resource intensity of the effect. |
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### Lighting
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| **Property** | **Description** |
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| ------------------------------ | ------------------------------------------------------------ |
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| **Ambient Light Probe Dimmer** | Controls the influence of light probes on the cloud volume. A lower value suppresses the ambient light and produces darker clouds overall. |
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| **Sun Light Dimmer** | Controls the influence of the sun light on the cloud volume. A lower value suppresses the sun light and produces darker clouds overall. |
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| **Erosion Occlusion** | Controls how much Erosion Factor is taken into account when computing ambient occlusion. The Erosion Factor parameter is editable in the custom preset, Advanced and Manual Modes. |
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| **Scattering Tint** | The color to tint the clouds. |
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| **Powder Effect Intensity** | Controls the amount of local scattering in the clouds. When clouds have a lot of local details due to erosion, a value of **1** provides a more powdery aspect. |
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| **Multi Scattering** | Controls the amount of multi-scattering inside the cloud. Higher values make lighting look more diffuse within the cloud. |
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### Shadows
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| **Property** | **Description** |
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| -------------------------------- | ------------------------------------------------------------ |
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| **Shadows** | When enabled, HDRP evaluates the Volumetric Clouds' shadows. The Volumetric Clouds shadow is rendered independently of the shadow map toggle of the directional [Light](Light-Component.md). |
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| - **Shadow Resolution** | Specifies the resolution of the volumetric clouds shadow map. |
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| - **Shadow Distance** | The size of the area to render volumetric cloud shadows around the camera. |
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| - **Shadow Opacity** | The opacity of the volumetric cloud shadows. |
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| - **Shadow Opacity Fallback** | Controls the shadow opacity when outside the area covered by the volumetric clouds shadow. |
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### Cloud map and cloud lookup table
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The **Cloud Map** and **Clout LUT** Textures define the shape and look of volumetric clouds. Both of these Textures are [channel-packed](Glossary.md#channel-packing) where each channel contains a separate grayscale Texture with a specific purpose. These two maps are not trivial to author, so it is best to only set **Cloud Control** to **Manual** if your project requires very specific clouds and you can use tool assistance to generate the maps.
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For the **Cloud Map**, the color channels represent:
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* **Red**: Coverage. Specifies the density of the clouds across the Texture.
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* Values closer to **0** represent an area of the clouds less affected by noise.
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* values closer to **1** represent an area of the clouds more affected by noise.
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* **Green**: Rain. Specifies the areas of the clouds that are lighter/darker.
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* Values closer to **0** represent an area of the clouds with less rain that are lighter in color.
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* Values closer to **1** represent an area of the clouds with more rain that are darker in color.
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* **Blue**: Type. Maps along the cloud lookup table's horizontal axis to specify cloud properties at the world position the texel Texture represents.
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For the **Cloud LUT**, the color channels represent:
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* **Red**: Profile Coverage. Determines the density of the cloud based on its height within the cloud volume.
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* **Green**: Erosion and shaping. Determines which areas of the cloud volume are more susceptible to erosion and shaping. Values closer to 1 mean the cloud is more susceptible to erosion and shaping.
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* **Blue**: Ambient Occlusion. A multiplier that HDRP applies to the ambient probe when it calculates lighting for the volumetric clouds.
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When importing these two map Textures, disable **sRGB**. For best results, do not use any compression.
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As a reference, here is the procedurally generated cloud LUT used for advanced mode. You can clearly see the 3 types of clouds (mid-altitude on the left, high altitude in the middle and cumulonimbus on the right).
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Also, there is variations in the green and blue channels to specify more of less erosion and ambient occlusion depending on the cloud profile.
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Here is an example cloud LUT that can be used in manual mode. On the top image, the LUT is divided into 8 32px wide parts, each representing a cloud type with a specific profile and altitude. (stratus on the left and cumulus on the right)
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On the bottom left, the cloud map uses grayscale values to map which type of clouds is used. For exemple a radial gradient using thoses values creates a circular cloud as seen on the bottom right using the profile set on the cloud LUT.
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For more examples, you can get the [environment samples](HDRP-Sample-Content.html#environment-samples) from the package manager.
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**Note**: This cloud map is formatted differently to the cloud map that the [Cloud Layer](create-simple-clouds-cloud-layer.md) feature uses.
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