what i want to do is render and object with a shadow and composite but have the shadow be .5 in the alpha grey in the alpha channel so its just appears darker on that spot where the shadow is but still see the bottom layer or the composite. when i try and render out an object taht has a shadow the floor is included in teh alpha so i make add it to a scene layer and turn off visibility but then i get no shadow since there is no floor for the shadow to be on. How do you do this. thanks for your help