Lighting Overrides

The Lighting options globally control some lighting aspects of the rendering. For example, these options can be used to disable all shadows in your scene, or to use probabilistic light sampling to speed up test renders.

UI Path: ||Render Settings window|| > Overrides tab > Lighting rollout

Lights – Enables lights globally. Note: Disabling this will cause V-Ray to use the default lights. If you do not want any direct lighting in your scene, you must disable both this and the Default lights override parameter.

Export hidden lights – Determines whether or not lights marked as hidden (i.e., not Visible) will be exported to V-Ray.

Auto – Lights with animated visibility are exported to V-Ray only for frames where they are visible. Invisible lights (lights with the  Visibility option disabled) are not exported. 
Always – Hidden lights are always exported to V-Ray regardless of whether it is rendering or creating a .vrscene file.  
Never – Hidden lights are never exported to V-Ray, even if they become visible during animation.

Default lights – Enables the usage of the default lights when there are no light objects in the scene or when you have disabled lighting globally (see the Lights parameter). 

Shadows – Enables shadows globally. When using V-Ray GPU renderer, this option is not available.

Ignore shadow and light linking – When enabled, V-Ray ignores all light linking in the scene.

Disable self-illumination – Disables the rendering of self-illuminated objects (objects assigned a VRayLightMtl). When using V-Ray GPU renderer, this option is not available.

Photometric lights scale – Globally changes the strength of all the photometric lights in the scene, such as IES lights or V-Ray lights, for which the units parameter is different from Default.

Light evaluation – Determines how lights are sampled in scenes with many lights. For more information, see the Adaptive Lights example below.

Adaptive lights – Uses information from the Light cache to determine which lights to sample. If a Light cache is not used, light tree sampling is used. Depending on the scene, it can be faster than the Full lights evaluation mode.
Full lights evaluation – V-Ray goes through each scene light and evaluates it at each shading point. In scenes with many lights and lots of GI bounces, this leads to a lot of shadow rays being traced and rendering can become extremely slow.  
Light tree – V-Ray selects a variable number of suitable finite light sources based on proximity and evaluates only those. This mode may speed up the Light Cache and Brute Force calculations for scenes with lots of lights. It can also reduce flickering due to missed light sources. 

Number of lights – Number of lights from the scene that are evaluated by V-Ray when the Light evaluation parameter is set to Adaptive. Lower values make the rendering go faster, but the result is noisier. Higher values cause more lights to be computed at each hit point, thus producing less noise but increasing render times.