This page gives some basic details about the Caustics Render Element and how it is used in compositing.
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 the same object or on other objects. The Caustics Render Element stores the effects that are generated with Caustics photon mapping, enabled from the Caustics rollout under the V-Ray GI Render Settings. This render element is useful for enhancing or toning down caustic effects in the composite.
UI Path: ||Shading viewport|| > Shader Tree > Add Layer button > V-Ray Render Elements > V-Ray Additional Outputs > Caustics
This render element is enabled and controlled through the V-Ray Additional Outputs properties.
Enable Caustics – Enables the Render Element.
Name – Sets a custom name for the Caustics Render Element.
Deep Output – Specifies whether to include this Render Element in deep images.
Apply Color Mapping – Applies the color mapping options specified in the Color mapping rollout of the V-Ray Main Render Settings.
The Caustics Render Element is useful for changing the appearance of caustic elements after rendering in a compositing or image editing application. Below is an example of its use.
Original Beauty composite
Caustics Render Element
The VRayCasutics Render Element is added to the Beauty render to form the final image.
The Reflective Caustics and Refractive Caustics options of the GI Render Settings cause a similar effect in the final rendering, but these caustics do not show up in the Caustics Render Element.