The fog serves to naturally limit the scene visual range. By means of the fog color element the fog color may be defined. If the fog is in the switched off state, it will be switched on. A color can be specified like Peter system’s other colors either by the color constant element, or by the compound color components to color element. By setting the value equal -1 instead of setting a fog color the fog can be switched off. If the fog is switched on by some other fog commanding elements, then the fog color is default set according to the current setting of the scene background color.