Additional info, example images, and demo scenes to be added.

Table Of Contents


Cinema 4D Advanced Caustics Settings

Maya Advanced Caustics Settings

3ds Max Advanced Caustics Settings

Houdini Advanced Caustics Settings

Katana Advanced Caustics Settings


Cinema 4D Caustics

Maya Caustics

3ds Max Caustics

Houdini Caustics

Katana Caustics

For more information please see the Photon Mapping for Caustics page.


Enables or disables the rendering of Caustics.


Specifies the caustics Mode to be used from the following options:

Light-emitted photons are independent from the camera settings, so fly-through animations can get away with generating the photon map once (on the first frame) and re-using it for all other frames.

If, however, photon-emitting lights move or material settings are animated, a new photon map will have to be generated.


Specifies where to save or load the caustics data depending on the chosen caustics mode as covered below.


Specifies the upper limit number of photons that can be stored in the "Blur Radius."

Higher values will allow the photon shooting algorithm to store more photons per unit area which means a larger memory requirement but not necessarily improved image quality! 

We recommend leaving this setting at the default value.

This setting does not limit the total number of photons in the scene that are shot from lights, that is specified by the "Number of Photons to Emit" found under the Photon section of a Redshift light.

Blur Radius

Controls the distance in world units around each shaded pixel that will be used to find photons.

Higher values mean smoother but blurrier results while lower values mean sharper but potentially more splotchy results. 

This setting is very closely tied to the number of photons shot from the lights. The more photons that lights have been configured to shoot the more the search radius can be shrunk without splotchy artifacts. If too few photons are shot from the lights the search radius has to be increased in order to not be splotchy. 

Fast Irradiance

When enabled, it allows Redshift to use a faster, pre-processed approximation that requires less searching for blurry effects.

Searching for photons during final rendering can be time-consuming and might slow down the render, "Fast Irradiance" allows caustics that are more blurry to render faster. 

The preprocessing step happens after the photons have been computed and might take a few seconds but the savings when rendering are worth it, so it is recommended that you leave this option enabled.

Trace Depths

Cinema 4D Trace Depths

Maya Trace Depths

3ds Max Trace Depths

Houdini Trace Depths

Katana Trace Depths


Specifies the number of times photons can bounce around the scene for reflections.

If you are rendering caustics and don't want reflective caustics but only want refractive caustics, you can try limiting the reflection trace depth to zero.


Specifies the number of times photons can bounce around the scene for refractions.


Specifies the maximum number of times photons can bounce around the scene for both reflections and refractions.

This means that if the individual trace depth value for reflections or refractions is higher than the Combined Depth the resulting render will still be capped at the Combined Depth value.