The ExponentialFog leaf node extends the Fog leaf node by adding a fog density that is used as the exponent of the fog equation. The density is defined in the local coordinate system of the node, but the actual fog equation will ideally take place in eye coordinates.
The fog blending factor, f, is computed as follows:
f = e-(density * z) where
z is the distance from the viewpoint.
density is the density of the fog.
In addition to specifying the fog density, ExponentialFog lets you specify the fog color, which is represented by R, G, and B color values, where a color of (0,0,0) represents black.