Free Indigo Renderer

The free Indigo renderer at http://www2.indigorenderer.com is an "unbiased render engine", meaning that it works purely based on physical properties. Similar in concept to the more famous and commercial Maxwell renderer.

Free but not open-source (at the moment). Commercial use is allowed with some minor limitations. There is support for Blender, 3ds max/VIZ, Cinema4D, SketchUp, Maya and XSI.

Windows only.