rib-mode is intended to be an (X)Emacs plugin in order to add syntax highlighting and indentation automatically to the text editing of RenderMan® Interface Bytestream (RIB) files that are in ASCII. The plugin code is in Lisp which is interpreted by the Emacs environment upon application startup.
I was unable to find such a plugin on the web, yet I do know that those using RenderMan tools also use Emacs editors. For example, there is a plugin for the RenderMan Shading Language (very similar to the C language), but none for the scene description interface known as RIB (a pascal-like language). RIB is intended to be human readable and editable to allow for the highest level of control of your scenes without resorting to C programming.