More optically correct than Ron's QuickGlass(), but slightly slower because of the math. Just like Ron's QuickGlass... with a RGrad as the control, it can be used for lens warp/dewarp (if the camera had a perfect lens)
It takes 2 input images;
The first to be refracted (warped)
The second for thickness or height (control)
(the macro is made of 2 nodes, 3 if you choose to invert the thickness input)