Shrimp is a visual workflow to the RenderMan shader creation, written on top of the FLTK2 library and using OpenGL for scene display. It will let you connect blocks of functions in a visual fashion much like an electronic CAD package, and it will create a preview from the connected shaders (surface, displacement, light, etc). Once satisfied, you can export the resulting shaders and use them in your 3D scenes using any RenderMan compliant engine, such as Aqsis, 3Delight, or PRMan.