Opposition loops in 3D

Okay, at this point you may be interested in outer planets, i.e. planets outside the orbit of Earth. Here it is: Regard the helio- and geocentric view, trace the planet orbit in 3D and watch the opposition loops. The outer planets actually do exactly this movement relative to the stars in the night sky. For special orbits the orbits are closed. You find some examples when you click the buttons on the left side. You can also chose some default planets as well as Ceres (which shows wonderful loops by the way) on the right side.