The extinction coefficient is raised to a power equal to the distance the transmitted ray travels through the object. The overall intensity of specularly transmitted rays will be proportional to this factor multiplied by the surface's body color multiplied by the transparency of the object. The default value is equal to the index of refraction of the atmosphere surrounding the eye. If a light source illuminates a translucent surface from the side opposite that from which a ray approaches, illumination computations are performed, using the given color as the surface's diffuse color, and the given exponent as the Phong highlight exponent. The resulting color is then scaled by the surface's translucency.
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. Add global low-altitude mist of the specified color. The color of a ray is modulated by a fog with density that varies linearly with the difference in z coordinate 1 between the ray origin and the point of intersection. The thinness values specify the transmissivity of the fog for each color channel.