Background color

mainprogram@backgrd4.f
subroutine  backd (n1, n2, rd)

Description: This program gives the color to the background.

Input variable:
  n1 : The number of the step in which the color of the ground changes
  n2 : The number of the step in which the sky of the ground changes
  rd : The angle per one step
Drawing example: backgrd4.wrl