renderman.escapestudios.com but you cannot access it unless you have an account and they are NOT cheap. Below is an excerpt explaining how they created the groundplane in the Pixar Short "Boundin'":

Quote - First, the groundplane problem is solved using a combination of procedural textures and hand-painted low resolution control maps. This leverages the powerful “what versus where” approach to shading - procedural textures determining what, texture maps determining where. This technique combines the unlimited resolution of procedural textures with the directability of hand-painted maps.

The beauty of this approach is that it's totally doable within Poser 5+ ..... it'd be a great service if BagginsBill wrote a book.