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This page provides 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 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: ||Display Render Settings button|| > Render Elements tab > Caustics



To use render elements, select from the Available render elements column and click the Add button to add the passes you wish to generate at render time. When you render the scene, the added render elements listed in the column on the right, will also render, which can be viewed from the VFB window's channel drop-down menu.

For more information on the parameters on this dialog, see the Render Elements tab page.



The parameters for this render element appear in the Attribute Editor under Extra V-Ray Attributes.

Enabled – When enabled, the render element appears in the V-Ray Virtual Frame Buffer.

Deep output – Specifies whether to include this render element in deep images.

Filename suffix – The text added to the end of the rendered file, when saved as a separate file (e.g. myrender.caustics.vrimg).

Apply color mapping – Applies the color mapping options specified in the Color mapping rollout of the V-Ray tab in the Render Setup window to this render element. This option is enabled by default.

Denoise – Enables the render element's denoising, provided the Denoiser render element is present.


Common Uses

The Caustics Render Element is useful for changing the appearance of rendered caustic effects with a compositing or image editing application. Below is an example of its use.



Original Beauty composite


Caustics Render Element








Tinted Caustics Render Element


Darkened caustics




Compositing Formula

vrayRE_Casutics + Beauty = Final Image





  • The Reflective Caustics and Refractive Caustics options on the GI section in the Render Settings window cause a similar effect in the final rendering, but these caustics do not show up in the Caustics Render Element.

  • This render element is not supported with V-Ray GPU rendering.
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