This is a legacy documentation space! Please refer to V-Ray Next for Rhino help for most up-to-date information.

This page provides details on the Caustics rendering settings in V-Ray for Rhino.


Page Contents



In order to calculate the caustics effects, V-Ray uses a technique known as photon mapping. It is a two-pass technique. The first pass consists of shooting particles (photons) from the light sources in the scene, tracing them as they bounce around the scene, and recording the places where the photons hit the object surfaces. The second pass is the final rendering, when the caustics are calculated by using density estimation techniques on the photon hits stored during the first pass.

Caustics are not supported in VR Camera and Stereo Camera modes.



UI path: ||V-Ray Asset Editor|| > Right Flyout > Caustics





Enabled – Turns rendering of caustics on and off.

Multiplier – Controls the strength of the caustics. This parameter is global and applies to all light sources that generate caustics. If different multipliers for the different light sources are desired, then use the local light settings.

Note: This multiplier is cumulative with the multipliers in the local light settings.

Search Distance – When V-Ray needs to render the caustics effect at a given surface point, it searches for a number photons on that surface in the area surrounding the shaded point (search area). The search area is a circle with the original photon at the center, and its radius is equal to the Search distance value. Smaller values produce sharper, but potentially noisier caustics; larger values produce smoother, but blurrier caustics.

Max Photons – Specifies the maximum number of photons that will be considered when rendering the caustics effect on a surface. Smaller values cause less photons to be used and the caustics will be sharper, but perhaps noisier. Larger values produce smoother, but blurrier caustics. The special value of 0 means that V-Ray will use all the photons that it can find inside the search area.

Max Density – Limits the resolution (and thus the memory) of the caustics photon map. Whenever V-Ray needs to store a new photon in the caustics photon map, it will first look if there are any other photons within a distance specified by this parameter. If there is already a suitable photon in the map, V-Ray will just add the energy of the new photon to the one in the map. Otherwise, V-Ray will store the new photon in the photon map. These options allows many photons to be shot (and thus get smoother results) while keeping the size of the caustics photon map manageable.




Disk Caching

Mode – Controls the mode of the irradiance map:

New map – When enabled, a new photon map will be generated. It will overwrite any previous photon map left over from previous rendering.
From file
– When enabled, V-Ray will not compute the photon map but will load it from a file. Hit the Browse button on the right to specify the file name.

Keep File – When enabled V-Ray keeps the photon map in memory after the scene rendering has finished. When disabled, the map is deleted and the memory it took is freed. Enabling this option can be especially useful if you want to compute the photon map for a particular scene only once and then re-use it for further rendering.

Auto-Save File – When enabled, V-Ray automatically saves the caustics photon map to the provided file when rendering is completed. Specifies the file location where the caustics photon map will be saved after rendering.