In the case of a 3d response surface a similar approach is used, with the first step being to find the local gradient vector at your current location. I think. Best place to read up on it is Matlab's help files.
Cheers
Greg Locock
New here? Try reading these, they might help FAQ731-376
A very interesting resource discussing N-R method for single and multi DOF cases is K.J. Bathe’s lecture 10 in "Finite Element Procedures for Solids and Structures". You can find it on MIT OpenCourseWare website. His book ("Finite Element Procedures") is also great but it skips the multi DOF case.