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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.

Phase Function – Controls how the light scatters inside the fog. Default value of 0.0 scatters the light uniformly in all directions. Positive value makes the light coming from a certain light source scatter mostly forward. Negative value results in it scattering backwards. See the Phase Function example below for more information.

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.

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.

For more information, see the Volumetric Caustics example below. 

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.

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Scatter GI – When enabled, the fog also scatters global illumination. Note that this can be quite slow. In many cases, global illumination within the fog can be substituted with a simple emission term. When this option is enabled, the currently selected global illumination algorithm in the V-Ray settings are used to accelerate GI inside the volume (e.g. the light cache or  or brute-force). For more information, see the Scatter GI and Scatter bounces example and the Importance of GI example below. 

Scatter bounces – When Scatter GI is enabled, this controls the number of GI bounces that are calculated inside the fog.

This sampler is used when any of the fog properties (color, density or emission) is mapped with a 3d texture. The sampler steps through the volume, evaluating volumetric textures and lighting, until it leaves the volume (if the fog is contained within a volume), or until the accumulated volume transparency falls below a certain cut-off threshold, or until a specified number of maximum steps is reached.

Step size – – Determines the size of one step through the volume. Smaller steps produce more accurate results but are slower to render. In general, dense volumes require smaller step sizes than more transparent volumes. In practice, step sizes that are two to three times smaller than the Fog distance parameter work well. Step size is calculated in scene units.

Max steps – Specifies the maximum number of steps through the volume.

Texture samples – Determines the number of texture samples for each step through the volume. This samples textures more accurately than the volumetric lighting. It is useful in cases where the textures vary much faster than the lighting itself (e.g. for detailed fractal textures). For more information, see the Texture samples with Ray marching example below. 

Cut off threshold – Controls when the raymarcher stops traversing the volume. If the accumulated volume transparency falls below this threshold, the volume is considered opaque and tracing is aborted. Higher values make the rendering faster but may introduce artifacts. This parameter is not available when the render engine is set to CUDA.

Deep Output – Toggles writing deep data to the file. Note that enabling this option forces ray marching even for simple volumetrics which can cause slower rendering.

Fade out mode – – Allows you to choose between two different modes of fade out.

Fade out radius – Allows you to set a radius for the fade out of the fog.

Per Object Fade Out Radius – When enabled, the fade out effect is applied to each fog volume independently using the Fog Fade Out Radius Extra V-Ray Attribute.