Re: DataReference

Hi Doug,

> I have data of the type (x,y) -> (t,u,v)
> I display t as contours (IsoContour) and u,v as a vector field
> (Flow1X,Flow1Y). No problem so far, but I'd like to be able to turn each
> of them off and on via my GUI. I have done this sort of thing
> successfully by removing and adding DataReferences to the Display. But,
> for this case, there is one DataReference for the whole thing. I can't
> remove one (e.g. t countours) without removing the other (e.g. u,v
> vectors). Do I have to create 2 distinct Fields with types:
> (x,y) -> (t)
> (x,y) -> (u,v)

This will work.

> If so, then I'd like to have my generic data reading code create
> something like:
> (x,y) -> (t)
> (x,y) -> (u)
> (x,y) -> (v)
> But then, as far as I can tell, the Flow vectors won't work unless u and
> v are part of the same Field. Is that the case?

Yes, they must be part of the same Field.

> Then what do I do if I
> want to have individual contours of u and v also? Do I have to have
> multiple copies of data all over the place? Is there a better way to
> add/remove data from the Display?

Given a FlatField with the MathType ((x, y) -> (u, v)) you can map:

  u -> Flow1X
  v -> Flow1Y
  u -> IsoContour
  v -> IsoContour

and get flow vectors plus contours of both u and v.  If you
want to turn flow, u contour and v contour all on and off
independently, then you'll need multiple FlatFields (or
another suggestion below).  No need for multiple copies of
the float u and v values though, just use copy = false in
calls to FlatField.setSamples() and FlatField.getFloats()
and repeat the same float[] arrays inside various float[][]
arrays passed to setSamples().

Another way to do this (JMet does it) is to create a complex
Tuple object with MathType:

  ((select1 -> ((x, y) -> (u, v))),
   (select2 -> ((x, y) -> u)),
   (select3 -> ((x, y) -> v)))

and to give each of the FieldImpl's (selectN -> ...) a domain
set Integer1DSet(2), where one range value is the FlatField
((x, y) -> ...) you want to display, and the other range value
is a FlatField with missing value (just don't call its
setSamples() method).  Then construct ScalarMaps of each selectN
to SelectValue.  The advantage of this approach is faster
toggling speed.

Bill Hibbard, SSEC, 1225 W. Dayton St., Madison, WI  53706
hibbard@xxxxxxxxxxxxxxxxx  608-263-4427  fax: 608-263-6738

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