Rendering shadow/reflection but not the plane itself
Ok. So I have an object that's lying on a plane, casting a nice shadow - or creating a nice reflection. I want to use the finished image on the web.
But, we have a catch 22 here. In order for Maya to render a shadow or a reflection, it needs to render the entire plane beneath the object, meaning that there won't be an alpha channel, meaning that I can't use the resulting image on any background.
So, how do I render only the shadow/reflection on a surface and not the surface itself? Can it even be done? I want the shadow to be a part of the alpha channel, so it can be used on any background. Ditto for a reflection.
Is it possible?