Mapping the input of an image via nodes.

So I’ve figured out how to get an image to be painted on regardless of the size of the object it’s on (so I don’t need to use UV mapping), but I need to do the same thing using nodes.

The method I used was to input an image into a texture slot, map the texture via cube method to an empty, and all was well.

However, if I try to input the image via a texture node (and use the material’s map input), or input the texture using materials nodes, I can’t seem to replicate the same behavior.

So any ideas on how to map an image using nodes without UV mapping?