Fog 3D effect
The Fog 3D effect
simulates fog by behaving as though a scattering medium is in the
air that makes objects look more diffuse as they get more distant
along the z axis.
This effect works with 8-bpc, 16-bpc, and 32-bpc color.
Note: As with all effects in the 3D Channel effects category, the
Fog 3D effect depends on depth information from image sequence files
of the kind rendered out of a 3D application. For general information
on 3D Channel effects, see
About 3D Channel effects. For information about simulating fog
in After Effects, see
Fog, smoke, clouds.

Original (upper-left), Gradient Layer (lower-left), and with
Fog 3D applied (lower-right)
- Fog Start Depth
- Where along the z axis the diffuse scattering begins.

To determine the depth of an object, click it in
the Composition panel or Layer panel using the Selection tool while
the effect is selected.
- Fog End Depth
- Where along the z axis the diffusion reaches its maximum.
- Scattering Density
- Determines how quickly the scattering occurs. The higher the
value, the more dense the fog appears from its starting point.
- Foggy Background
- Creates a foggy background (default). Deselect to create transparency
at the back of the 3D scene for compositing on top of another layer.
- Gradient Layer
- (Optional) A grayscale layer to use as a control layer, the luminance
values of which apply to fog density. For example, use the Turbulent Noise
effect to create a swirling control layer for atmospheric fog. Make
sure that the dimensions of the gradient layer are at least as great
as the dimensions of the 3D scene layer.
- Layer Contribution
- How much the gradient layer affects the fog density.