There are two things under the name RenderMan: 1. Pixar's Photorealistic RenderMan, short PRMan, which is a renderer produced and sold by Pixar. You can buy that renderer directly from Pixar if you like. 2. RenderMan as a standard for the interface/API to a renderer. In theory, any renderer that complies to that standard can be used with any application that complies to that standard. In practice it may require a little hand-editing of the resulting RIB files. Since RenderMan is only a interface standard and says absolutely nothing about the implementation, RenderMan compliance has nothing to do with image quality or rendering algorithms. For example, many RenderMan compliant renderers do not support raytracing, some do. Most of them don't support radiosity. Pixar's PRMan itself didn't support raytracing until november 2002, btw. Poser supports the RenderMan interface ever since, thus you are able to use RenderMan renderers to render Poser scenes. However, since that export is a little dated (e.g. not supporting transparency maps or Poser 5 hair), I wrote my own RenderMan export that can be downloaded for free from my web page. The FireFly renderer in Poser 5 is mostly, but not completely RenderMan compliant. It uses the same algorithm as PRMan does (REYES.raytracing hybrid). 3Delight, the renderer that will ship with Studio is RenderMan compliant (which implies that you can use it with any version of Poser already). It is also a hybrid REYES renderer/raytracer.