I have a scene where a reflective object needs to be in it's own separate render layer from the rest of the world. I am looking to have one layer which includes the object, it's shadows casted on the world, as well as the reflections of the world, and the world in a separate layer. Is there an easy way to pull this off by using render layers?
Ultimately, I am having this reflective object moving through the world and having the camera track the object. The object will be motion blurred in post for part of it, and another part has the world being motion blurred and not the object.
This has little to do with Render Layers technology vs. good old fashioned 3D compositing. Render Layers can but probably don't really assist you in what your trying to do here.
The idea is this: either copy your scene to a new file or a Render Layer if you want, then make all reflecting objects primary visibility "0" but leave on visible in reflect/refract.
Now create a shader and assign it to your reflecting object and make it 100% reflective and render this pass. Then Render another version of this scene with only the reflected Ball (But no reflection, make a simple lambert shader and assign) to get it's alpha channel only which would be used as your mask in AE or similar comp. In other words you don't want a final alpha that has channels for the invisible reflected objects.