Once I came across a publication that was about using complex numbers in 3D, but I just look at it and put it down, later on, I tried to find that pamphlet but never could, have any one come across anything that refers to 3D use of complex numbers?

Second request is that any of you has used the Maple's Symbolic

Mathematics to do feed back and control, Matlab's extensive tool boxes are all numerical, any one seen anything symbolic in relation to feed back and control?