This page provides information on the Lighting overrides rollout in the Render Settings.
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.
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.
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).
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.
Full 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. When GPU rendering, this will introduce probabilistic light calculations but will not allow the Number of lights parameter to be set. Older V-Ray scenes with the Probabilistic Lights parameter disabled, will default to using this option. For more information, see the below.
Uniform Probabilistic – V-Ray randomly chooses the specified number of lights and evaluates only those. Lower values make the rendering faster, but potentially more noisy. Higher values cause more lights to be computed at each shading point, thus producing less noise, but increasing render times. This option makes it possible to render images that would otherwise take a very long time, at the expense of possibly introducing more noise into the rendering. When GPU rendering, this will introduce probabilistic light calculations. Previous V-Ray 3 scenes that had the Probabilistic Lights parameter enabled, will default to using this option. For more information, see the below.
Adaptive – Uses information from the Light cache to determine which lights to sample. If a Light cache is not used, uniform sampling will be used. Depending on the scene, it can be faster than the Full evaluation and Uniform Probabilistic mode.
Number of lights – Number of lights from the scene that are evaluated by V-Ray when the Light evaluation parameter is to either Adaptive or Uniform Probabilistic. To achieve a positive effect from probabilistic light sampling, this value must be lower than the actual number of lights in the scene. Lower values make the rendering go faster, but the result is potentially more noisy. Higher values cause more lights to be computed at each hit point, thus producing less noise but increasing render times. For more information, see the below.
Example: Probabilistic Lights
Below is an example rendering of a scene with 1089 sphere lights with the Cutoff threshold set to 0.0. Both images were rendered with the Progressive image sampler and ran for the same amount of time. When probabilistic lights are enabled, the image is much cleaner as V-Ray manages to compute more GI rays (which are the main source of noise in this scene).
Probabilistic lights is Off
Probabilistic lights is On (8 lights)