[pstricks] iso contour lines

[Cyrille Piatecki]

Is there a way to plot a surface with the isocontour line projected on the x,y plan  without being obliged to give to pstriocks the explicit equatin of the curves
-- not the surface ?

I dont' know if it is possible to pass some parameters like the change of origin in command like \rput. If it's not the cas and not a mistake of mine It will be great.

Thanks
  Cyrille Piatecki