Fog

Category: Volume

Shader Family: Volume

Output: Color

Implements a vertical layer of fog between two specified distances. This shader uses Poisson distribution to calculate the density of the fog, where the fog is at its density at half the layer's height and drops to half its maximum value at its edges. In addition to this vertical component, the volume of the fog is specified by a start and stop distance from the ray, which corresponds to the ray entering and leaving the volume.

This shader is also used to create a depth fading effect when applied to a render pass.

NoteThis distance clipping only works correctly for primary rays; secondary illumination such as reflected or refracted rays are treated as if they originated from the camera. This means that for start distances greater than 0, the first segment of the length as given by the start parameter of the secondary ray is not affected by the fog, even if the ray originates in the middle of the fog layer.

Name	The shader's name. Enter any name you like, or leave the default.
Start, End Distance	Specifies the distance between where the fog begins (completely transparent) and where it ends (completely opaque). Fog appears only between these two distances, and the fog density is linearly interpolated between these them.
Transparency Rate	Specifies the density of the fog. 0 = no fog and will not obscure light; 1 = opaque fog.
Transmissive Color	Specifies the color of the fog that light rays are faded into.
Light Rays	Specifies whether or not light rays are also attenuated by fog. When on, light illumination is subject to fog attenuation; when off, lights can illuminate objects at any distance regardless of fog.

Render Tree Usage

To apply this volume effect to an object (as opposed to a scene) connect this shader to the Volume input of the Material node. Volume shaders cannot be expanded or built upon in the render tree.