Page History

Enabled – Turns indirect illumination on and off.

Primary Rays – Specifies the GI method to use for primary bounces.

Irradiance map – Causes V-Ray to use an irradiance map for primary diffuse bounces. See the Irradiance Map Settings section for more information.
Brute force – Specifies direct computation for primary diffuse bounces. See the Brute Force Settings section for more information.
Light cache – Specifies the light cache for primary diffuse bounces. See the Light Cache Settings section for more information.

Secondary Rays – Specifies the GI method to use for secondary bounces.

None – No secondary bounces will be are computed. Use this option to produce skylit images without indirect color bleeding.
Brute force – Specifies direct computation for secondary diffuse bounces. See the Brute Force Settings section for more information.
Light cache – Specifies the light cache for secondary diffuse bounces. See the Light Cache Settings section for more information.

Image Modified

 The second rollout of the Global Illumination settings allows adjustment of the Secondary GI engine - either Brute Force or Light Cache. For more information on each, please refer to their respective page.

Image Modified

Light Cache as Secondary GI engine

Image Modified

Brute Force as Secondary GI engine

Caustics – Enables or disables rendering of caustics.

Progressive Caustics

Multiplier – Controls the strength of the caustics. It is global and applies to all light sources that generate caustics. Should a different multipliers for each light source be needed, the V-Ray properties of each light should be edited. Note: this multiplier is cumulative with the multipliers in the local light settings.

It should also be noted that changing multipliers, while useful for artistic purposes, will result results in physically-inaccurate scenes.

Search Dist (Pixels) – Specifies the initial photon lookup radius in pixels. The Progressive mode works only in Pixels.

Image Modified

Multiplier – Controls the strength of the caustics. This parameter is global and applies to all light sources that generate caustics.

Search Distance Units – Determines in what units the Search distance parameter is specified - World units or Pixels.

Search Dist (World)/(Pixels) – When V-Ray renders the caustics effect at a given surface point, it searches for a number of photons on that surface in the area surrounding the shaded point (search area). The search area in fact is a circle with center the original photon and its radius is equal to the Search distance value. Smaller values produce sharper, but perhaps more noisy caustics; larger values produce smoother, but blurrier caustics.

Max Photons – Specifies the maximum number of photons that is considered when rendering the caustics effect on a surface. Smaller values cause fewer photons to be used and the caustics are sharper, but noisier. Larger values produce smoother, but blurrier caustics. The special value of 0 means that V-Ray uses 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 first checks if there are any other photons within a distance specified by Max density. If there is already a suitable photon in the map, V-Ray just adds the energy of the new photon to the one in the map. Otherwise, V-Ray stores the new photon in the photon map. Using this options allows you to shoot many photons (and thus get smoother results) while keeping the size of the caustics photon map manageable.

Calculation Mode/Disk Caching

Mode – Controls the mode of the irradiance map:

New map – When enabled, a new photon map will be is generated. It will overwrite overwrites any previous photon map left over from previous rendering. 
From file – When enabled, V-Ray will does not compute the photon map but will load loads it from a file. Press the Browse button on the right to specify the file name.
Progressive – Uses advanced sampling techniques and is able to trace as many photons as required without suffering the memory constraints of traditional Photon Mapping techniques.

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 is saved after rendering.

Image Modified

GI Caustics rollout is available only in Advanced mode.

Reflective Caustics – Allows indirect light to be reflected from specular objects like mirrors, etc. Note that this is not the same as Photon Mapped Caustics, which represent direct light being reflected by reflective surfaces.

Refractive Caustics – Allows indirect lighting to pass through transparent object like glass, etc. Note that this is not the same as Photon Mapped Caustics, which represent direct light going through transparent objects. You need refractive GI caustics to get skylight through windows, for example.

Image Modified

These controls allow an ambient occlusion term to be added the global illumination solution. Ambient Occlusion rollout is available only in Advanced mode.

Enabled – Turns ambient occlusion on or off.

Radius – Determines the amount of area (in Scene units) where the ambient occlusion effect is produced.

Occlusion Amount – Specifies the amount of ambient occlusion. A value of 0.0 will produce 0 produces no ambient occlusion.

Image Modified