I assume the most straightforward way to draw planetary rings (such as those around Saturn) is to use a texture that is transparent everywhere except for the rings, and then place the planet in the middle of the texture and that's it.
The problem with this approach is that I don't know how to shadow the area of the rings texture that is behind the planet (which isn't lit by the sun). At the moment I have a rings texture that is permanently lit and a planet that darkens in the areas where it's not lit by the sun. The planet revolves around the sun, so the lit/shadowed areas are constantly changing.
Any suggestions on how to apply shadow on the rings?