Shadows on invisible objects
 

Is there a way to, in this composition, make the white plane (below the cube) invisible and keep the cube and its shadow visible?

Thanks for support!

http://img335.imageshack.us/img335/2544/samplegg2.jpg

you should be able to use a 'use background' shader.

when you apply said shader to the white plane and render, you'll notice that the alpha channel for your render no longer includes the plane itself, just the shadow that was cast onto it.

It worked. Thanks!