Linear material over non-uniform object?

[Matthew Hagerty]

Greetings,

I need a material that will fade a color (or modify illumination) over 
the length of an object.  Think of a wall, on the left I'd like white, 
on the right some color, with a nice even fade across the surface.  That 
much I figured out.  What I'm having a problem with is when I need one 
or more corners in the wall, I can't figure out how to start at one end 
and follow the wall's "path" to the other end while fading the color.

Currently my wall is an analytic polyhedron, but it could be a mesh too, 
as long as it has sharp corners.  My current material works fine as long 
as the wall is straight, but I really need the linear fading to continue 
around the wall's corners.

I'm hoping someone can give me some ideas on how to do this, I'm at a 
total loss.

Thanks,
Matthew