A while ago I was looking for a way to do footprints in sand. I know you can project an image on the sand, but the image would have static lighting, meaning, for example, if the sun were to travel across the sky, there would be no change in the footprint images shadows. Is there a shader that I could use as a projection that would essentially draw the footprint on the terrain, but with a bumpmap elemnt to it so the projected image would change with the lighting changes?
Take a look at the Decal framework on Showoff section.
Not completely sure, but I have watched couple of the videos and saw that the footprints are implemented so you might want to take a look at it. Not sure if it uses bump maps or not