To set VRayEnvironmentFog, go to Render Settings > > Overrides > > Volumetrics.
Enable the Use environment volume optionand as an Environment volume map. Click Add New Item to add a volumetric map. You can add one or multiple maps. As an Environment Volume, select the VRayEnvironmentFog volumetric.
This is the default way of setting an environment fog in the scene.
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Fog Gizmo
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If you want to set an Environment fog gizmo, make the geometry object a member of the VRayEnvironmentFog set. You have to first set the VRayEnvironmentFog as global Environment volumetric as shown above.
This way the object becomes a constraint for the fog. The benefit of a fog gizmo is, a camera inside the gizmo renders the fog.
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Fog Container
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To create a fog container, create the geometry object first. Note that the VRayEnvironmentFog should not be set as an Environment volumetric!
Assign a V-Ray material that has opacity control. Here we use VRayMtl and make the object fully transparent by setting the Opacity Map to black color.
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To make only certain light object(s) to affect the Environment Fog, navigate to the Outliner and make the selected light(s) a member of the Environment Fog set.
Set the Light Mode to either Override shape lights or Intersect with shape lights.
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Common
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Enabled – Enables or disables the VRayEnvironmentFog.
Color – Defines the color of the fog when it is illuminated by light sources. You can also use a texture map to drive the fog color. For more information, see the Color example below.
Emission – Controls the fog emission (self-illumination). You can use this parameter to substitute the ambient illumination inside the fog, instead of using GI. For more information, see the Emission example below.
Emission Multiplier– Multiplies the Emission parameter.
Fog Distance – Controls the fog density. Larger values make the fog more transparent, while smaller values make it denser. For more information, see the Fog Distance example below.
Fog Density – A multiplier for the Fog distance parameter. It allows a texture to be used for the density of the fog.
Transparency – Controls the color of the volumetric shadows and the tint for the objects seen through the fog. Brighter colors make the fog more transparent, while darker colors make it more dense at a distance given by the Fog distance parameter. See the Transparency example below and the How to create underwater shots with fog color transparency video for more information.
Fog Height – If the fog is not contained within a volume, it is assumed to start from a certain position along the scene's up-axis and continue downward indefinitely. This parameter determines the starting point along the up-axis. For more information, see the Fog Height example below.
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When the fog is added to a gizmo, the Height parameter has no effect. When the fog is added to the environment or in a container, then the Height parameter determines the starting point in scene units.
See the How to Set Up section for more details on how to use the fog in a container, or a gizmo, or as an environment effect.
Light Mode – Allows you to specify which lights are considered when rendering the environment fog. It is used when you have certain lights affecting just specific objects in the scene while another group of lights is affecting the environment fog. Note that V-Ray GPU does not support light modes yet.
No lights – The lights in the scene do not affect the environment fog. Use shape lights(default) – The lights attached to the environment fog set are ignored. Only the lights affecting the shape where the fog resides are used. Override shape lights – Only the lights affecting the environment fog set are considered. Intersect with shape lights – Only lights that are affecting both the shape and the environment fog set are considered. Add to shape lights – Both lights that are affecting the shape and the environment fog set are considered.
Ior – Index of Refraction for the volume, which describes the way light bends when crossing the material surface. A value of 1.0 means the light does not change direction.
