Introduction to LuxRender
From LuxRender Wiki
LuxRender is a physically based and unbiased rendering engine. Based on state of the art algorithms, LuxRender simulates the flow of light according to physical equations, thus producing realistic images of photographic quality.
The program is based on the PBRT project, but differs from that program by focusing on production rendering and artistic efficiency instead of scientific purposes.
LuxRender is free software - both for personal and commercial use - and is licensed under the GPL. The program runs on Windows, Mac OS X and Linux. Fully functional exporters are available for many popular 3D packages.
LuxRender comprises an interactive user interface and exporters for various 3D programs, including Blender, 3ds Max and XSI. Additionally, a command line tool is available. For developers we provide a C/C++ API that allows embedding LuxRender into third-party applications. The program runs on Windows, MacOS-X and GNU/Linux platforms and can be downloaded for free.