V-Ray lights are designed specifically to work with V-Ray and optimize its features. V-Ray also provides shadow options for standard Maya lights and utilities to assist in the lighting process.
The VRayLightRect, also known as the V-Ray Rectangle light or an "area light" is a planar light source with the shape of a rectangle or circular disk. Rectangle lights are useful for simulating man-made light sources in an interior environment, such as lamps. A rectangle light can have any one of two different shapes: plane or disc. For more information, see Rectangle Light | VRayLightRect.
The VRayLightSphere is a VRay Light object in the shape of a sphere, casting light outward in all directions. For more information, see Light Sphere | VRayLightSphere.
A dome light (also considered an area light) creates light within a dome or spherical shape to create a traditional global illumination setup. This Light is frequently used to load HDRI environment images. For more information, see Dome Light | VRayLightDome.
A Sun light is a spherical light source placed at a specific location which simulates the sun in the sky. A Sun light has some unique qualities:
For more information, see Sun and Sky System | VRaySun.
Photometric lights are designed to simulate a light source's distribution pattern exactly as they behave in real life by loading and using an IES (Illumination Engineering Society) file. An IES profile contains details about the light's behavior, such as how the light passes through fresnel lenses, its intensity, and its and falloff. For more information, see Photometric Lights | VRayIES.
The VRayLightMesh can create light sources that have volume and shape defined by geometry in the scene, without the need to use self illuminated objects and global illumination. For more information, see Mesh Light | VRayLightMesh.
The Light Meter helper shows how a scene is illuminated, which aids in troubleshooting or in adjusting lights. For more information, see Light Meter | VRayLightMeter.
Another UI tool that can be extremely helpful when setting up and adjusting like is the V-Ray Light Lister. It provides quick access to many of the most important attributes for all the lights in your scene. It also makes it easy to select, turn off, or solo a light to see it's contribution to your scene's lighting. For more details, please see the Light Lister page.
The V-Ray Light Lister is a window that gives users an easy access to all the lights in a scene, whether V-Ray or Maya lights. Using this interface allows users to adjust many commonly used parameters for lights such as a light's intensity and color, as well as quick access to renaming, selecting, and enabling/disabling lights. For more on the Light Lister, click here.