9.5.2

924 • CHAPTER 18
THE SHADERS • 925
Volumetric
Volumetric adds greatly to render time. If the option is disabled, the basic color of the fog is all
pervading. Light sources will have no effect. This is normally sufcient to simulate fog in a fractal
valley. With Volumetric enabled, all light sources will be taken into account. If the light sources cast
soft shadows, and if there are objects in the beam, the objects will cast shadows in the fog.
Frequency
Increase Frequency for ner detail in the X, Y and Z directions.
Type
Set Type to the desired falloff for the fog: Linear, Exponential or No Decrease. Linear decreases the
fog intensity along the Y-axis of the texture axes. Exponential decreases the fog intensity along the
Y-axis of the texture axes. No Decrease means constant fog density.
Thickness, Decrease
The lower the Thickness value, the thinner the fog. Decrease controls the volume (or depth) of the
fog that is generated.
Turbulence
Turbulence species the degree of swirl within the fog (0% = no turbulence).
Amplitude
Amplitude species the average size of the rotating turbulence cells (rolling fog).
T-Frequency
T Frequency controls the speed of the swirling fog (0% = no movement).