color_map
// texture pigment {} attribute
// create a smooth color gradation map
color_map {
// [ END_VAL color red R green G blue B filter F transmit T]
[ 0.1 color red 0.0 green 0.0 blue 0.0]
[ 0.3 color red 0.8 green 0.4 blue 0.2]
[ 0.5 color red 0.0 green 0.0 blue 0.0]
[ 0.7 color red 0.0 green 0.0 blue 0.8 filter 0.5]
[ 1.0 color red 0.8 green 0.8 blue 0.8 filter 1.0]
// (---alternative form---)
//[ 1.0 color rgbf <0.8, 0.8, 0.8, 1.0> ]
} // color_map