Have a look at how Caustics works in Corona Render 4 in Cinema 4D.

Plenty of people strive for more realistic images, and smaller details count. That is what caustics are considered the one thing that looks great but is rarely attainable. Caustics are typically a separate effect because they are so expensive in terms of resources and time. With the release of Corona 4, the team included the ability to create both reflective and refractive caustics in a render.

Check out this tutorial that covers everything that you need to know about working with the caustic effect in Cinema 4D. The tutorial defines what the impact is, and how to enable caustics and how to optimize production scenes for best rendering speeds.