Volume Fog provides
a fog effect in which the fog density is not constant through 3D
effects such as puffy, cloudy fog that appears to drift and break
up in the wind.
Volume fog added to
Volume Fog renders only
in Camera or Perspective views. Orthographic or User views don’t
render Volume Fog effects.
To use volume fog:
- Create a Camera or Perspective view of
- Choose Rendering Environment.
- Under Atmosphere on the Environment panel,
The Add Atmospheric Effect
dialog is displayed.
- Choose Volume Fog, and then click OK.
- Set the parameters for volume fog.
NoteIf there are no objects
in your scene, rendering shows only a solid fog color. Also, with
no objects and Fog Background turned on, volume fog obscures the
To create a volume fog gizmo:
Volume fog gizmo surrounds
- In the Helpers category of the Create
panel, choose Atmospheric Apparatus from the pop-up menu.
- Click one of the buttons to choose a
gizmo shape: SphereGizmo, CylGizmo, or BoxGizmo.
- Drag the mouse in the viewport to create
You create Gizmos in
much the same way as their matching geometry types. Drag the mouse
to create the initial dimensions. The Sphere gizmo has an additional
Hemisphere check box that turns the sphere into a hemisphere.
In addition, each gizmo has a Seed spinner and
a New Seed button. Different seed values generate different patterns.
Clicking the New Seed button randomly generates a new seed value
To assign volume fog to a gizmo from
an apparatus modify panel:
- Open the Modify panel of an apparatus.
- Open the Atmospheres & Effects rollout.
- Click Add.
- Select Volume Fog from the Add Atmospheres
dialog and click OK.
- Highlight Volume Fog from the Atmospheres
list and click setup to adjust the Volume Fog parameters.
To assign a gizmo to volume fog from
the Environment panel:
- On the Volume Fog Parameters rollout,
click the Pick Gizmo button.
- Click a gizmo in the viewport.
The name of the gizmo appears in the list field
When you render, the
volume fog will be confined to the shape of the gizmo.
To remove an assigned gizmo:
- In the Environment dialog, go to the
Volume Fog Parameters rollout
- Select the gizmo name from the pop-up
- Click Remove Gizmo.
This action doesn’t delete the gizmo from the
scene, but simply unbinds it from the fog effect.
The Volume Fog Parameters
rollout appears when you select Volume Fog under Effects in the
Environment dialog. The Volume Fog Parameters rollout has the following
By default, volume fog
fills the entire scene. However, you can choose a gizmo (an atmospheric
apparatus) to contain the fog. The gizmo can be a sphere, a box,
a cylinder, or some combination of these.
- Pick Gizmo
Click to enter Pick mode
and click an atmospheric apparatus in the scene. The apparatus contains
the volume fog when you render. The name of the apparatus is added
to the apparatus list.
Multiple apparatus objects
can display the same fog effect.
You can pick multiple
gizmos. Click Pick Gizmo and then press H.
This opens the Pick Object dialog, which lets you choose multiple
objects from a list.
Changing the dimensions
of a gizmo changes the region that fog affects, but doesn't change the
scale of the fog and its noise. For example, reducing the radius
of a spherical gizmo crops the fog, and moving the gizmo changes
the fog's appearance.
- Remove Gizmo
Removes a gizmo from
the volume fog effect. Select the gizmo in the list, and then click Remove
- Soften Gizmo Edges
Feathers the edges of
the volume fog effect. The higher the value, the softer the edges.
Range=0 to 1.0.
TipDon't set this value
to 0. At 0, Soften Gizmo Edges can cause aliased edges.
Sets the color for the
fog. Click the color swatch, and then select the color you want
You can animate the color
effect by changing the fog color at a nonzero frame with Auto Key on.
Increases density exponentially
with distance. When turned off, density increases linearly with distance.
Activate this check box only when you want to render transparent
objects in volume fog.
TipIf you turn on Exponential,
increase the Step Size value to avoid banding.
Controls the fog density.
Range=0 to 20 (anything over that tends to obliterate the scene).
Left: Original scene
Right: Increased fog
- Step Size
Determines the granularity
of the fog sampling; the "fineness" of the fog. A large step size
creates coarse (and to some extent, aliased) fog.
- Max Steps
Limits the amount of
sampling so that computing the fog doesn't take forever (literally).
This is especially useful when the fog is of low density.
When both Step Size and
Max Steps have low values, aliasing results.
- Fog Background
Applies the fog function
to the background of the scene.
Left: Original scene
Right: Noise added
to the fog
Noise options for volume
fog are comparable to the noise options for materials.
Choose one of three types
of noise to apply.
The standard noise pattern.
An iterative fractal
An iterative turbulence
Reverses the noise effect.
Dense fog becomes translucent and vice versa.
- Noise Threshold
Limits the noise effect.
Range=0 to 1.0. When the noise value is above the Low threshold
and below the High threshold, the dynamic range stretches to fill
0-1. This makes for a smaller discontinuity (First order instead
of 0 order) at the threshold transition, and thus produces less potential
Sets the low threshold.
Left: Fog with noise
Right: Changing uniformity
creates "blobby" fog
Ranges from -1 to 1 and
acts like a high-pass filter. The smaller the value, the more transparent
the volume is with discrete blobs of smoke. Around -0.3 or so your
image begins to look like specks of dust. Because the fog becomes thinner
as this parameter gets smaller, you'll probably need to increase
the density or the volume will start to disappear.
Sets the number of times
the noise is iteratively applied. Range=1 to 6, including fractional values.
Enabled only for Fractal noise or Turbulence.
Determines the size of
the tendrils of smoke or fog. Smaller values give smaller tendrils.
Left: Fog with noise
Right: Decreasing the
Controls the speed of
the wind. If you have Wind Strength also set to greater than 0,
the fog volume animates in accordance with the wind direction. With
no Wind Strength, the fog churns in place. Because there's an animation track
for phase, you can use the Function Curve editor to define precisely
how you want your wind "gusts" to occur.
- Wind Strength
Controls how fast the
smoke moves away from the wind direction, relative to phase. As mentioned
above, if the phase is not animated then the smoke won’t move, regardless
of the wind strength. By having the phase animate slowly with a
large wind strength, the fog moves more than it is churns.
- Wind from the
Defines the direction
the wind is coming from.