The Default Medium

The default medium is the medium which surrounds and encompasses all of the objects in the scene; it is the ``air'' through which eye rays usually travel before hitting an object. The properties of the default medium may be modified through the use of the atmosphere keyword.

$\begin{defkey}{atmosphere}{[{\em N\/}] [{\em atmospheric effects}]} If given, {\... ...o every object in the scene (e.g., rays emanating from the camera). \end{defkey}$

    /*
     * Red sphere on a grey plane, with fog.
     */
    eyep 0. -10. 2.
    atmosphere fog  .8 .8 .8 14. 14. 14.
    plane 0 0 0  0 0 1
    sphere diffuse 0.8 0 0   1.5  0 0 1.5