rendering no background but have a shadow
 

I am coming to the completion of my group animation and we were wanting to have our characters doing things as the credits go by. Our problem is that we cant figure out how to have the background of the render all white but show the character and a shadow where the ground would be located. Any help would be apprecitated
thanks

Put a poly or nurbs ground plane in your scene. Make your camera's background color white. Put a "Use Background" material on the plane. Should find it in the hypershade.

Ooh, thanks for the tip mike.
That'll come in handy,

thanks alot,

i hope to post the final version to hear some opinions of the animation when its all done and over with