returning the detected material??

[WhytWulf]

Does anyone know how I can detect the texture/material on the -Z axis.
IE: for a FPS type situation where the player walks from, grass to metal, I want to know when this happens, and play a different footstep sound.

I'm thinking it would probably involve collision of a vector along the -Z axis with a node, but how can I find out what texture is hit, is where I am stuck..