Quote - Winterclaw:
For applying it to upward surfaces, can you use one of the math tools to do that?  Like the Du Dv variables?

You mean vertical surfaces?  Displacement wouldn't be affected, because it works along the direction of the normal.  It would still work.  (Or do I misunderstand the issue?)

But, I for one would love for bagginsbill to elaborate on the Du Dv node, et al, because I see some node names that appear to be partial derivatives, and -depending on whether they are read or write operators-  could enable a tear to follow a natural path down a cheek, a marble ball to run along a kugelbahn track, or pick out the outside "corners" of a geometry mesh to selectively apply scuff marks in a realistic distribution.  :D

Poser 12, in feet.  

OSes:  Win7Prox64, Win7Ultx64

Silo Pro 2.5.6 64bit, Vue Infinite 2014.7, Genetica 4.0 Studio, UV Mapper Pro, UV Layout Pro, PhotoImpact X3, GIF Animator 5