Carrara will calculate g-buffers that will export (post-render) with a tiff image that can be used as photoshop alpha channels for various effects. The Distance and 3D position (y-axis) g-buffers might be worth trying. The depth-of-field function renders in Carrara, but it might be the wrong effect for you.

Scaling a shader might be analogous to using an ordinary texture map and tiling it in the y-axis only.