Pixar have recently released the latest version of their Renderman renderer for free to use under a non-commercial license.
Renderman is Pixar’s in house rendering solution that uses it’s own lighting and shading system that is available for use via the appropriate plugin. Renderman has been in development for 25 years and has been used in many of Pixar’s short and feature films as well as being a tool used invarious blockbuster films from Terminator 2 to The Lord of the Rings.
Renderman 21 is compatable with Maya, KATANA, Houdini and Blender. It is available from https://renderman.pixar.com/