mapping streamlines to scalar value

This message is in MIME format. Since your mail reader does not understand
this format, some or all of this message may not be legible.

Content-Type: text/plain



On a Gridded2DSet I am plotting a scalar value (density) as well as
streamlines for a 2D vector field (velocity).  Right now I have the density
mapped to the ZAxis and my streamlines lie in the z=0 plane.  My goal is to
have the streamlines lie on top of the density surface.  I came up with


(( x , y ) -> ( density )) -> ( u , v )


which clearly violates the FunctionType constructor.  Are there any easy
ways to accomplish this?  Thanks in advance.