YafaRay is an open source raytracing render engine. As an open source project, users and developers have free access to the source code and it is free, as in free speech.
Ray tracing is a rendering technique for generating an image by tracing the path of light through the 3D scene. This technique tries to reproduce the natural behaviour of light and its particular effects on surfaces, such as reflection and refraction, caustics and indirect lighting. More Info »
YafaRay works as a render engine. An engine consists of a 'faceless' computer program that interacts with a host 3D application to provide very specific raytracing capabilties "on demand". Blender 3D is the host application of YafaRay.
By using python scripts, YafaRay takes advantage of the new ID Property mechanism of Blender to retrieve most of the scene data, without adding any custom code to Blender. Other specific parameters are set up by a python-coded settings interface used from Blender.