color - defines the color of the fog when it is illuminate by light
sources. You can also use a texture map to drive the fog color.
Fog distance - controls the fog density.
Larger values make the fog more transparent, while smaller values make it
more dense. You can also control the density with a texture map.
Fog emission - controls the fog emission
(self-illumination). You can use this parameter to substitute the ambient
illumination inside the fog, instead of using GI.
Scatter GI - when on,
the fog will also scatter 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 on,
the currently selected global illumination algorithm in the V-Ray settings
will be used to accelerate GI inside the volume (e.g. the
photon map or
Scatter bounces - when Scatter GI is
enabled, this controls the number of GI bounces that will be calculated
inside the fog.
Fog height - if no atmospheric gizmos are
specified, the fog is assumed to start from a certain Z-level height and
continue downward indefinitely. This parameter determines the starting point
along the Z-axis. If there are atmospheric gizmos listed in the
Nodes section, this parameter is ignored.
VRayEnvironmentFog can use either of two
algorithms to calculate volumetric lighting. The first algorithm is a simple
exponential sampling scheme, which is used when there are no texture maps
specified. In this mode, VRayEnvironmentFog takes
a number of random points inside the volume and calculates the volumetric
lighting at those points. The second algorithm is a
raymarching scheme, which is used when any of the volume properties
are mapped with a texture. In that case,
VRayEnvironmentFog traverses the fog volume in small steps,
calculates the volume properties at each step and computes the volume
This sampler is used when there are no texture maps specified, in which
case the volume properties are the same everywhere.
Subdivs - this parameter determines the
number of points inside the fog at which volumetric lighting is evaluated.
Smaller values for this parameter render faster, but may produce noise in
the image. Higher values render longer, but with less noise.
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
there are atmospheric gizmos specified), 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
Texture samples - determines the number of
texture samples for each step through the volume. This allows to sample
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).
Cutoff threshold - this parameter controls
when the raymarcher will stop traversing the volume. If the accumulated
volume transparency falls below this threshold, the volume will be
considered opaque and tracing will be aborted. Higher values make the
rendering faster but may introduce artifacts.
Max steps - specifies the maximum number
of steps through the volume.
section allows you to map various properties of the fog - its color, density
and emission. Note that whenever a texture is used,
VRayEnvironmentFog will use the raymarching sampler to calculate the
You can use any 3ds Max 3d texture map to define the volume properties.
Note that you should use World XYZ mapping for
Color texture - this texture controls the
fog color when it is illuminated by light sources.
Density texture - this texture allows you
to modify the texture density. Black values in the texture correspond to
perfectly transparent fog; white areas correspond to the density specified
by the Fog distance parameter.
Emission texture - this texture controls
the fog light emission (self-illumination).
section allows you to specify gizmos that confine the fog atmospheric
effect, and also to specify which scene lights contribute to the
illumination of the volume.
Gizmos - A list of atmospheric gizmos
within which the fog will be calculated.
Use all lights - when on, all scene lights
contribute to the illumination of the volume, and the
Lights list is ignored.
Lights - a list of lights that affect the volume when
Use all lights is off.