Depending on the version of maya your suing you could use the closest point on mesh or the closest point on surface to do the collisions.
open the script editor and go to help -> mel command refrence and search thatfor the flags as its up to you what you want it to do.
Also put history echo all commands on so the script editor displays everything thatyou do so you get a grasp of the commands and how maya uses them
"No pressure, no diamonds" Thomas Carlyle