Planètes en orbite  

#declare Moon_Orbit_Radius   =  4;
#declare Earth_Orbit_Radius  = 16;
//--------------------------------
#declare Moon_Radius   = 0.7;
#declare Earth_Radius  = 2.0;
#declare Sun_Radius    = 3;
//--------------------------------

#declare Moon = // Lune
sphere{ <0,0,0>,Moon_Radius
        texture{ ... }}
#declare Earth =  // Terre
sphere{ <0,0,0>,Earth_Radius
        texture{ ... }}
#declare Sun   =  // Solei
light_source{ <0,0,0>
              color rgb<0,0,0>
 looks_like{
 sphere{ <0,0,0>,Sun_Radius
         texture{ pigment{ ... }
                  finish{ ambient 1,
                          diffuse 0}
                } // end of texture
       } // end of sphere
   } // end of looks_like
 } // end of light_source
//--------------------------------

#declare Time = clock + 0.00;
 // Time = 0 à 1 dans une année !!!
#declare Earth_around_Sun_Rotation
 = 360*Time;   // 1 tour par an !!!
#declare Moon_around_Earth_Rotation
 = 360*Time*12; //12 mois!!!
#declare Earth_Rotation
 = 360*Time*360; // ~ 365 jours !!!
//--------------------------------

//-----------------------------------------------------------
union{ // Earth + Moon  // Terre et Lune
  object{ Earth
          rotate <0,Earth_Rotation,0>
        } // end Earth
  object{ Moon
          translate <Moon_Orbit_Radius,0,0>
          rotate <0,Moon_around_Earth_Rotation,0>
        } // end Moon

 // puis les deux (comme "union") meuvent par Earth_Orbit_Radius en +x.

  translate <Earth_Orbit_Radius,0,0> 
 // et pivotent autour il Solei
  rotate <0,Earth_around_Sun_Rotation,0>

} // fin de union de "Earth + Moon"

object { Sun }
//-----------------------------------------------------------