Light Node

Light node is generally used for producing self-illuminated surfaces. This material's light emission can be used as indirect as well as direct illumination in the scene.

This allows for light sources of any shape, and may even be assigned at the object level and at the face level for self-illuminating only portions of a mesh.

Light Color – This parameter controls the color of the light material.

Color Multiplier – A multiplier for the Light Color.

Opacity –  A texture to use as opacity for the material. Note that making the material less opaque does not affect the intensity of the self-illumination color. This is so that you can create perfectly transparent materials that nevertheless still emit light.

Emit on Back Side – When enabled, makes the object emit light from its back side as well. If this is off, the material is rendered as black on the back sides.

Compensate Exposure – Used when rendering with the V-Ray Physical Camera. When enabled the intensity of the material is adjusted to compensate for the camera exposure. Note that this option is disabled when the Direct illumination is enabled.

Multiply by Opacity – When enabled, the color of the light material is multiplied by the opacity texture. Otherwise, the color and opacity act independently (so-called additive transparency).