well lets just say i want to render a shere that i want to composite on live footage later. i setup the lighting to be the same as the live footage so teh shadows are the same. Well assuming i dont have to worry about reflections how do i render only the shere to to compositied on live footage with a shadow. and in the alpha channel of a frame the shadow is grey, where the sphere is its white and everything else is black? i dont have a site to upload screenshots to show you