Options
Cast shadows - when on (the default), the light casts shadows. Turn this option off to disable shadow casting for the light.
Double-sided - when the light is a planar light source this option controls whether light is beamed from both sides of the plane. This field has no effect for Sphere or Dome light sources.
Invisible - this setting controls whether the shape of the VRayLight source is visible in the render result. When this option is turned off the source is rendered in the current light color. Otherwise it is not visible in the scene. Note that this option only affects the visibility of the light when seen directly by the camera or through refractions. The visibility of the light with respect to reflections is controlled by the Affect specular option.
Ignore light normals - normally, the surface of the source emits light equally in all directions. When this option is off, more light is emitted in the direction of the source surface normal.
No decay - normally the light intensity is inversely proportional to the square of the distance from the light (surfaces that are farther from the light are darker than surfaces which are closer to the light). When this option is on the intensity will not decay with distance.
Skylight portal - when this option is on, the Color and Multiplier parameters are ignored; instead the light will take its intensity from the environment behind it.
Simple portal - this option is only enabled if the Skylight portal option is on. It tells the VRayLight that there is nothing of interest behind the light itself, and so the environment color can be used directly. Normally, the portal light takes its color from whatever objects are behind it. In order to do this, the light traces additional rays, which may slow down the rendering. Turning this option on makes the rendering of portal lights faster.
Store with irradiance map - when this option is on and GI calculation is set to Irradiance map V-Ray will calculate the effects of the VRayLight and store them in the irradiance map. The result is that the irradiance map is computed more slowly but the rendering takes less time. You can also save the irradiance map and reuse it later.
Affect diffuse - this determines whether the light is affecting the diffuse properties of the materials.
Affect specular - this determines whether the light is affecting the specular of the materials.
Affect reflections - this determines whether the light will appear in reflections