Atmospheric Effects

Any number of atmospheric effects may be associated with the default medium (``air'').


\begin{defkey}{fog}{\evec{color} \evec{thinness}} Add exponential fog with the specified {\em thinness} and {\em color}. \end{defkey}
Fog is simulated by blending the color of the fog with the color of each ray. The amount of fog color blended into a ray color is an exponential function of the distance from the ray origin to the point of intersection divided by the specified thinness for each color channel. If the distance is equal to thinness, a ray's new color will be half of the fog color plus half its original color.


\begin{defkey}{mist}{\evec{color} \evec{thinness} {\emzero scale}} Add global lo... ...}, which scales the difference in altitude used to compute the fog. \end{defkey}


\begin{defkey}{fogdeck}{{\em altitude} {\em offset} \evec{scale} {\em chaoscale}... ...-altitude fog, with transmissivity modulated by a chaotic function. \end{defkey}