title: matplotlib 2D slice of 3D data
body: <p>I haven't been able to find anything on this, maybe because I don't have the right nomenclature (i.e. I don't know exactly how to ask for it), but anyway, I have a 3D numpy array "a".  I would like to identify and plot the 2D surface where a=0.  To make clear, the data is double precision floats smoothly varying over 3D space.  It is highly likely that the surface a=0 will "thread between" the points of the array, and not exactly lie right on any of them.  So I need something that can interpolate to find the a=0 surface and plot it.  Does matplotlib have a ready-made routine for doing this?</p>