Caustics is an effect that is produced when light rays are reflected or refracted by the materials within a scene, which can produce light patterns on objects in the scene. The Caustics Render Element displays these effects, generated with Caustics photon mapping. It is enabled from the Caustics rollout under the GI tab in the Render Settings window. This render element is useful for enhancing or toning down caustic effects in the composite.

UI Path: ||V-Ray|| > Render Elements > Caustics