//  Globe gridlines, with poles on Z-axis
//  Last edited on 1999-02-13 18:39:34 by stolfi

//  Requires
//    gridlines_thickness
//    gridlines_focus_lat
//    gridlines_polar_lat
//    gridlines_tropic_lat
//    gridlines_line_texture
//    gridlines_dot_texture
//  Defines
//    gridlines

#declare cf = cos(gridlines_focus_lat);
#declare sf = sin(gridlines_focus_lat);

#declare cp = cos(gridlines_polar_lat);
#declare sp = sin(gridlines_polar_lat);

#declare ct = cos(gridlines_tropic_lat);
#declare st = sin(gridlines_tropic_lat);

#declare gridlines_dot =
  sphere{ <0,0,0>, 0.5*gridlines_thickness }

#declare gridlines_meridian =
  intersection{
    torus{ 1, 0.5*gridlines_thickness }
    plane { < -1,0,0 >, 0 translate cf*x }
  }

#declare gridlines_focus_parallel =
  torus{ cf, 0.5*gridlines_thickness rotate 90*x }
  
#declare gridlines_polar_parallel =
  torus{ cp, 0.5*gridlines_thickness rotate 90*x }

#declare gridlines_tropic_parallel =
  torus{ ct, 0.5*gridlines_thickness rotate 90*x }

#declare gridlines_noon_parallel =
  torus{ 1, 0.5*gridlines_thickness rotate 90*x }

#declare gridlines =
  union{
    union{
      object{ gridlines_meridian rotate < 000,000,000 > }
      object{ gridlines_meridian rotate < 000,000,030 > }
      object{ gridlines_meridian rotate < 000,000,060 > }
      object{ gridlines_meridian rotate < 000,000,090 > }
      object{ gridlines_meridian rotate < 000,000,120 > }
      object{ gridlines_meridian rotate < 000,000,150 > }
      object{ gridlines_meridian rotate < 000,000,180 > }
      object{ gridlines_meridian rotate < 000,000,210 > }
      object{ gridlines_meridian rotate < 000,000,240 > }
      object{ gridlines_meridian rotate < 000,000,270 > }
      object{ gridlines_meridian rotate < 000,000,300 > }
      object{ gridlines_meridian rotate < 000,000,330 > }

      object{ gridlines_focus_parallel  translate < 0, 0, +sf > }
      object{ gridlines_polar_parallel  translate < 0, 0, +sp > }
      object{ gridlines_tropic_parallel translate < 0, 0, +st > }
      object{ gridlines_noon_parallel   translate < 0, 0, 0 > }
      object{ gridlines_tropic_parallel translate < 0, 0, -st > }
      object{ gridlines_polar_parallel  translate < 0, 0, -sp > }
      object{ gridlines_focus_parallel  translate < 0, 0, -sf > }

      texture{ gridlines_line_texture }
    }
    object{ gridlines_dot 
      texture{ gridlines_dot_texture }
      translate <0, 0, 1>
    }
  }