Vray - is a rendering engine that is used as an extension of certain 3D computer graphics software. It developing by Chaos Software Ltd.
It is a rendering engine that uses advanced techniques, for example global illumination algorithms such as path tracing, light cache, irradiance maps and directly computed global illumination.
Vray is used in the development of film productions and multi-million dollar game productions.
It is also used extensively in making realistic 3D renderings for architecture. :)