' - - File: XII_Contour6D
' 3D directed field + a contour based upon the z-values, H.

' Plot a "simple surface" directed field.
r = 6 :  er = 0.1  :  sg =0.2

H{x,y} = (16 - x^2 -y^2) / 4
F{x,y} = Diff[H,x]
G{x,y} = Diff[H,y]

PlotDirField[F, G, H, {-4,4,15}{-4,4,20}]

PlotContour1[H,{-r,r,-r,r} { 2,2} {-3,3,0.5} {er,sg}]





