// uses image color index as height, extends along X-Z axes
// from <0 0 0> to <1 1 1>
height_field {
  png               // the file type to read (tga/pot/pgm/ppm/png/sys)
  "plasma3.png"     // the file name to read
//  [smooth]        // smooth surface normal
//  [water_level N] // truncate/clip below N (0.0 ... 1.0)
//  texture {...}
//  translate VECTOR | rotate VECTOR | scale VECTOR
}