Share 'Creating a simple Gaussian like NURBS surface'

Trying to reproduce the mill surface in this great video:   http://www.grasshopper3d.com/video/gcode-writer-for-surface?xg_source=activity   See the GH file attached. Used a 2D Gaussian function as this seems to be the closest to me. Need to give credits to   http://www.grasshopper3d.com/forum/topics/2d-contour-plot-and-zero-of-a-1d-function   where I borrowed some code for plotting a 2D contour…