Lumberyard
User Guide (Version 1.15)

Setting Global (Time of Day) Volumetric Fog

You can use global volumetric fog to simulate particles that are distributed uniformly along the ground and fall off exponentially with height above sea level. Global volumetric fog accurately accounts for time of day lighting and for scattered sunlight rays to produce halos around the sun.

Use the Anisotropy parameters to control the amount of sunlight that is scattered through fog and the direction. Set the Anisotropy (atmosphere) parameter close to 0 to achieve a uniform look across the entire sky. Set the Anisotropy (sun radial) parameter close to 1 to create a bloom effect around the sun.

The Radial blend parameters blend the Anisotropy parameters to create various effects. For example, you can create sun radial scattering by setting Radial blend mode to 1 and Radial blend factor to 1.

To set global volumetric fog parameters

  1. In Lumberyard Editor, click Tools, Other, Time Of Day.

  2. In the Time of Day Tasks pane, under Tasks, click Toggle Advanced Properties to view all parameters.

  3. In the Parameters pane, under Volumetric fog, adjust the following parameters as needed:

Parameter Description
Height (bottom)

Specifies a reference height for the vertical fog gradient. This is the height at which the fog color reaches the specified color at the top. For fog density, this value is the height at which the vertical density falloff reaches the specified density.

Density (bottom)

Specifies the fog density at the bottom. Values greater than 0 or less than 1 cause the fog to gradually fall off.

Height (top)

Sets the reference height for the vertical fog gradient. For fog color, this value is the height at which the specified color reaches the top. For fog density, this value is the height at which the vertical density falloff reaches the specified density.

Density (top) Specifies the fog density at the top. You can set the top density to a higher value than the bottom density. Doing so would reverse the vertical falloff and produce thick fog in the sky and clear views at the bottom. You can also set the top and bottom density values to be equal.

Volumetric fog computations treat a level as a continuous unbound volume. If you specify a density greater than 0 at the specified top height, the fog won't suddenly stop at that height. Instead the fog will continue to fall off gradually. The same action is true for bottom boundary or density values that are less than 1.

Global density

Sets the density of the global volumetric fog. Higher values create denser fog.

Ramp start

Specifies the distance from the camera at which the fog starts to render at 0 density.

Ramp end

Specifies the distance from the camera at which the fog ceases to render at 0 density.

Color (atmosphere)

Specifies the fog color for the atmosphere. For example, you can set the fog color to light blue (140, 230, 255) for midday, darker blue (90, 148, 164) for sunset or sunrise, and white for night time.

Anisotropy (atmosphere)

Adjusts the anisotropy for sun atmosphere scattering. Valid values: -1 to 1. Values less than 0 will shift the fog in the opposite direction of the sun. Values greater than 0 create a consistent appearance of atmospheric fog.

Color (sun radial)

Specifies the color of the glow around the sun.

Anisotropy (sun radial)

Adjusts the anisotropy for sun radial scattering. Values less than 0 will shift the glow effect to the opposite side of the sun. Values greater than 0 make the radial color visible even when looking away from the sun.

Radial blend factor

Blends the sun radial color with the atmosphere color. Valid values: 0 to 1. Set the value to 0 to turn off radial fog.

Radial blend mode

Adjusts the blend mode for blending between atmosphere fog and radial fog. Set the value to 0 to use additive blending. Set the value to 1 to use linear interpolation.

Color (entities)

Specifies the global fog color for volumetric lights, excluding the sun.

Anisotropy (entities)

Adjusts the appearance of volumetric fog entities based on the viewing angle in relation to the sun. 0 = isotropic | 1 = perfect forward | -1 = perfect backward in-scattering.

Range

Adjusts the maximum radius of volumetric fog. The default setting is 64.

In-scattering

Specifies how much light (including sun) is scattered by fog. Higher values create a foggier scene (fog density remains unchanged) with bigger and brighter glow effects.

Extinction

Specifies how much light the fog absorbs. Higher values create a thick, atmosphere effect that is tough for sun light to penetrate.

Analytical fog visibility

Adjusts the global visibility of analytical fog. Set the value to 0 to hide analytical volumetric fog. Set the value to 1 to display analytical volumetric fog.

Final density clamp

Sets the maximum density that the fog can reach. This enables the sky, horizon, and other bright, distant objects to be visible through dense fog. Setting this value too low can compromise depth perception and result in implausible visuals and apparent artifacts, especially when moving the camera.