Realistic light fixtures are essential for creating photoreal visualizations — both interior and exterior. In the real world, these fixtures can be very complicated combinations of light sources and diffuse, transmissive or reflective surfaces surrounding them in order to create the desired light distribution. However, accurately simulating the overall illumination from such fixtures is a computationally intensive task, and most often than not, they end up being simplified in order to get a result in a reasonable time frame.

The Cosmos library — included with most Chaos products — includes many light fixtures, some of which are provided by companies producing the original physical versions of these fixtures. As such, they are modeled in a realistic way in order to correctly represent the product in 3D scenes. While these models are very accurate, they may also be somewhat challenging to render.

The V-Ray Luminaires, introduced in V-Ray 7, provide a completely new way to efficiently and accurately render such light fixtures. In a pre-computation step, we calculate a very accurate version of the light field surrounding the light fixture — i.e., the amount of light emitted in any given direction from the surface of the luminaire — and store this in a file that accompanies the relevant Cosmos models. When the model is imported from the Cosmos library, in addition to the geometry and the light sources, a new type of light source is created as well, called a VRayLuminaire light. This light encompasses portions of the light fixture and emulates its emission when viewed from outside. The VRayLuminaire light references the precomputed light field and also allows to control aspects of the light fixture as a whole — including the color of the lights and their intensity.

Here is an example of a simple setup where a scene is lit by two light fixtures. Each fixture consists of a light source surrounded by a lamp shade as can typically be seen in the real world.

Rendering the scene without luminaire light fields in 21m 50s

The resulting sampling rate

Rendering the scene with luminaire light fields in 1m 1s

The resulting sampling rate

If a light fixture has a VRayLuminaire object attached to it, then control of the light emitted from the fixture, like intensity and temperature, should be handled from the VRayLuminaire object. However at this time, disabling a VRayLuminaire light simply disables the light field calculation and not the regular light sources that are a part of the light fixture. An easy way to disable all of the light emitted from the fixture is to set the intensity of the VRayLuminaire light to 0.0.

Similarly, in the VRayLightMix system, the original lights in the fixture and the VRayLuminaire light will appear separately; this is something that will be improved in subsequent V-Ray 7 releases.